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ARVO 2015 Annual Meeting Abstracts
163 Cornea biomechanics and keratoprosthesis
Sunday, May 03, 2015 3:15 PM–5:00 PM
Exhibit Hall Poster Session
Program #/Board # Range: 1099–1140/D0001–D0042
Organizing Section: Cornea
Program Number: 1099 Poster Board Number: D0001
Presentation Time: 3:15 PM–5:00 PM
An Engineering-based Methodology to Characterize the In
Vivo Nonlinear Biomechanical Properties of the Cornea with
Application to Glaucoma Subjects
Michael J. Girard1, 2, David Tan1, Marcus Ang2, Jod S. Mehta2, Liang
Zhang1, Cheuk Wang Chung1, Baskaran Mani2, Tin A. Tun2, Tin
Aung2. 1Biomedical Engineering, National University of Singapore,
Singapore, Singapore; 2Singapore Eye Research Institute, Singapore,
Singapore.
Purpose: To characterize the in-vivo nonlinear biomechanical
properties of normal and glaucoma corneas using a robust inverse
finite element approach.
Methods: The corneas of 12 subjects (3 normal, 3 ocular
hypertensive, 2 angle-closure, and 4 open-angle glaucoma;
IOP=14.9±3.1 mmHg; Age=61±16 years; CCT=560±42 μm) were
deformed (air jet) and their transverse cross-sections simultaneously
imaged using the Corvis ST Tonometer (Oculus, Wetzlar, Germany).
Since the Corvis cannot directly derive ‘true-engineering’
biomechanical properties, we propose a novel methodology that
uses Corvis images. Briefly, the corneal geometry of each subject
was digitally reconstructed and meshed using 8-node hexahedrons.
A Veronda-Westmann constitutive model that incorporated stretchinduced stiffening of the collagen fibrils was introduced. Stiffness
parameters were varied until model corneal displacements (affected
by IOP and air jet loading) matched those derived experimentally.
This was performed using an inverse finite element approach driven
by a global optimization algorithm (differential evolution). Such a
methodology was able to derive stress & strain (air jet induced), and
a unique set of biomechanical properties for each subject’s cornea.
Results: In all cases, our models matched the Corvis data well
(Figure). On average, corneas exhibited 9.05±2.29% maximum
effective strain and 65.5±10.9 kPa maximum effective stress as a
result of air jet loading. Corneas had an average initial stiffness of
0.08 MPa (95th percentile: 0.11 MPa) that increased to 0.31 MPa (95th
percentile: 1.02 MPa) at 5% strain, indicating nonlinear stiffening
behavior. Corneal bulk moduli were on average 5.49 MPa (95th
percentile: 17.6 MPa). No differences in mechanical properties
between groups could be reported due to the small sample size.
Conclusions: Our novel methodology can estimate ‘true’ in-vivo
corneal biomechanical properties that are likely more relevant than
surrogate parameters provided either by the Corvis or the Ocular
Response Analyzer. Our ultimate goal is to identify whether corneal
biomechanics could serve as a biomarker for glaucoma.
Commercial Relationships: Michael J. Girard, None; David Tan,
None; Marcus Ang, None; Jod S. Mehta, None; Liang Zhang,
None; Cheuk Wang Chung, None; Baskaran Mani, None; Tin A.
Tun, None; Tin Aung, None
Support: NUS Young Investigator Award (NUSYIA_FY13_P03,
Girard); NMRC STAR GRANT (NMRC/STaR/0023/2014; Aung)
Program Number: 1100 Poster Board Number: D0002
Presentation Time: 3:15 PM–5:00 PM
Corneal strains induced by ocular pulse and larger IOP
elevations
Elias Pavlatos1, Hong Chen1, Xueliang Pan2, Jun Liu1, 3. 1Department
of Biomedical Engineering, Ohio State University, Columbus, OH;
2
Center For Biostatistics, Ohio State University, Columbus, OH;
3
Department of Ophthalmology, Ohio State University, Columbus,
OH.
Purpose: To compare corneal strains induced by an ocular pulse
of a few mmHg with those during inflation from 5 to 30 mmHg in
the same eye to evaluate whether the ocular pulse associated strains
could predict the outcome of a standard mechanical testing, i.e.,
inflation.
Methods: Seventeen porcine globes were tested within 48 hours
postmortem. Whole globes were secured using a custom-built holder
and immersed in 0.9% saline. A 20G needle was inserted into the
anterior chamber and connected to a pressure sensor (P75, Harvard
Apparatus) to monitor the intraocular pressure (IOP). Another 20G
needle was connected to a programmable syringe pump (PHD Ultra,
Harvard Apparatus) to control IOP. The globes were preconditioned
with 5 pressure cycles from 5 to 30 mmHg and then equilibrated
at 16.5 mmHg for 15 minutes. The ocular pulse was simulated by
oscillating IOP between 15 and 18 mmHg at 1 Hz for 25 cycles,
and ultrasonic scans (radiofrequency data) were saved for the last 5
cycles. After equilibration at 5 mmHg for 15 minutes, the globe was
inflated from 5 to 30 mmHg with 0.5 mmHg steps every 15 seconds.
Ultrasonic scans were performed at each step. Corneal radial strains
were determined using an ultrasound speckle tracking technique
(Tang & Liu, J Biomech Eng 2012, 134(9)). For both the ocular pulse
and inflation tests, a stiffness index “b” was calculated by fitting the
nonlinear relationship between IOP and strain.
Results: For all seventeen globes, the average peak radial strain
induced by ocular pulse was 0.13 ± 0.03%. The average radial strain
at 30 mmHg in the inflation tests was 3.10 ± 0.72%. The correlation
between these peak strains was significant (R=0.671, p=0.003;
Figure 1). A representative strain map obtained from ocular pulse is
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
shown in Figure 2. The b-values, more representative of the overall
nonlinear relationship, were also significantly correlated (R=0.570,
p=0.017).
Conclusions: The strong positive correlation in maximum strain
magnitudes and b-values between ocular pulse and inflation
tests suggested that these two methods generated correlative
biomechanical evaluation of the cornea. While the inflation across
a large range of IOPs is difficult to implement in vivo, the naturally
occurring ocular pulse could be a feasible alternative to evaluate
corneal biomechanics in vivo.
Fig 1. Comparison of inflation and ocular pulse maximum strains.
Fig 2. Corneal strain map at peak pressure of ocular pulse.
Commercial Relationships: Elias Pavlatos, None; Hong Chen,
Ohio State University (P); Xueliang Pan, None; Jun Liu, Ohio State
University (P)
Support: NEI Grant RO1EY020929
Program Number: 1101 Poster Board Number: D0003
Presentation Time: 3:15 PM–5:00 PM
The Role of Iron II (Fe+2) as a Cross-linking Enhancer in CXL
Sarah Peterson, Pavel Kamaev, William A. Eddington, Marc D.
Friedman, David Muller. Avedro, Inc., Waltham, MA.
Purpose: Riboflavin (Rf) is used as a primary photosensitizer
for Corneal Collagen Cross-linking (CXL). Understanding the
underlying photochemical mechanisms provides insight into the
addition of additives for enhancement of cross-linking efficiency.
H2O2 is a byproduct of the Type I reaction in CXL. We investigated
the addition of transitional metals such as Fe+2 to drive H2O2 to OH
through a Fenton-like reaction in a porcine eye model.
Methods: Fresh whole globe porcine eyes were obtained <24 hours
postmortem in saline on ice from Sioux-preme (Sioux City, IA). Eyes
were cleaned and de-epithelialized with a dull blade, then soaked for
20 minutes in an incubator set at 37°C by using a rubber ring to hold
solutions (A) 0.1% Rf in distilled water or (B) 0.1% Rf with 0.5mM
Iron(II) sulfate heptahydrate (Sigma Aldrich) in distilled water on
the corneal surface. Eyes were placed in a beaker with a light oxygen
stream for 2 minutes, and pan-corneally irradiated for 8 minutes at
30mW/cm2 pulsed 1 second on: 1 second off, measured with a power
meter (Ophir, Inc.) at the corneal surface. Cross sections of cornea
were first measured using biaxial extensiometry (Eddington W, et al.
IOVS 2013;54:ARVO E-Abstract 1619), then analyzed using papain
digestion (Rood-Ojalvo S, et al. IOVS 2013;54:ARVO E-Abstract
5280).
Results: The results of extensiometry show Rf + Fe+2 obtained
markedly increased stiffness over Rf alone. This was corroborated by
the increase of fluorescence in corneal flaps digested with papain by
approximately 45% compared to Rf alone.
Conclusions: The addition of Fe+2 to Rf increases the efficiency of
corneal collagen cross-linking in a porcine eye model. The presence
of iron catalyzes the formation of highly reactive OH radicals from
H2O2. This makes more OH radicals available to further increase
collagen crosslinking per equivalent UV dose. Fe+2may be used as an
enhancer in riboflavin CXL.
Commercial Relationships: Sarah Peterson, Avedro, Inc. (E);
Pavel Kamaev, Avedro, Inc. (E); William A. Eddington, Avedro,
Inc. (E); Marc D. Friedman, Avedro, Inc. (E); David Muller,
Avedro, Inc. (E)
Program Number: 1102 Poster Board Number: D0004
Presentation Time: 3:15 PM–5:00 PM
Confocal Brillouin spectrometer for measuring corneal
biomechanics
Michael Bukshtab, Amit Paranjape, Marc D. Friedman, David
Muller. Avedro, Waltham, MA.
Purpose: Current methods for in-vivo measurement of corneal
biomechanics are inadequate. This presents an impediment to
diagnosis and treatment of corneal conditions such as keratoconus.
Brillouin spectroscopy provides a non-contact, objective method to
measure mechanical properties. This study developed a non-contact,
confocal Brillouin spectrometer, capable of millisecond signal
acquisition times, for measurement of corneal biomechanics.
Methods: A highly-sensitive confocal microscope-spectrometer
was built to detect Brillouin signal shifts. The system utilizes an
eye-safe, highly coherent, single-frequency, fiber-coupled laser at
780 nm wavelength, stabilized at the Rubidium D2 absorption line.
A polarization-extinction scheme and confocal fiber optic system
were used to collect Brillouin shifted light scatter. This system
in conjunction with a rubidium filtering cell (to reduce Rayleigh
scattering and stray-light of the excitation wavelength) analyzes the
Brillouin signal with an enhanced VIPA spectrometer and low-noise
EMCCD camera.
The system was tested by measuring fresh porcine corneas with and
without cross-linking. Crosslinking was performed at UVA doses
of 0 to 20 J/cm2 with irradiances of 3 to 30 mW/cm2 using 0.12%
riboflavin solution.
Results: Microsecond acquisition-time sensitivity for corneal
biomechanics was demonstrated via Brillouin spectroscopy
measurements. Brillouin spectral shifts ranging from 7.8 to 8.7 GHz
were observed for porcine specimens, with cross-linked eyes showing
linear increase as a function of CXL dose as compared to non-crosslinked eyes.
Conclusions: A non-contact, confocal Brillouin scanning
microscope-spectrometer is demonstrated. This device allows
measurement of the biomechanical, spatial distribution of corneal
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
tissue and is able to differentiate CXL treated tissue. This system
holds future promise as a tool to enhance corneal diagnostics and
corneal cross-linking treatments.
Commercial Relationships: Michael Bukshtab, Avedro (E); Amit
Paranjape, Avedro (E); Marc D. Friedman, Avedro (E); David
Muller, Avedro (E)
Program Number: 1103 Poster Board Number: D0005
Presentation Time: 3:15 PM–5:00 PM
Investigating the association between ocular biometry and
corneal biomechanics in healthy human
Daniela Oehring1, Christine Purslow1, 2, Phillip J. Buckhurst1,
Hetal Buckhurst1. 1Optometry, Plymouth University, Plymouth,
United Kingdom; 2School of Optometry & Vision Sciences, Cardiff
University, Cardiff, United Kingdom.
Purpose: The CorvisST (Oculus) and Reicherts Ocular Response
analyzer (ORA) provide in vivo measures of corneal biomechanics.
It is likely that the structure of the ocular globe affects the
biomechanics. The study assesses the association between corneal
biomechanics using CorvisST and ORA and theirs with axial length
(AL), refractive error and central corneal thickness (CCT) in healthy
eyes
Methods: Corneal biomechanics was assessed in 43 healthy adults
(18-40 yrs (25.2±7.0); 81% female, 19% male) with CorvisST and
ORA. The biomechanics of both eyes were evaluated randomized.
Measures of length (L), time (T) of the applanation point 1 (A1)
and 2 (A2) and the highest concavity (HC) were determined with
CorvisST. The ORA provided measures of corneal hysteresis
(CH) and corneal resistance factor (CRF). Refractive error [MSE
(D)] and AL were measured using cycloplegic autorefraction and
the Haag Streit LenStar. CCT was determined with Pentacam
(Oculus). Subjects were grouped according to MSE (D): myopic
(<-0.50) -2.96+/-1.99, AL 24.82+/-1.05mm, n=18; non-myopic
(≥-0.50) +0.80+/-1.23, AL 23.27+/-0.90mm, n=23. To evaluate the
relationship between MSE, AL and biomechanics a multivariate
variance analysis was conducted, using CCT and age as covariates.
Correlation coefficient was calculated CCT and age-adjusted
Results: Mean CCT was 559+/-37mm, CRF 13.0+/-11.6, CH 13.6+/12.7, A1T 7.12+/-0.25sec, A1L 1.79+/-0.04mm, A2T 21.98+/1.49sec, A2L 1.70+/-0.35mm and HC 16.71+/-0.61mm. Significant
correlation was found between MSE and AL (r=-0.826, p<0.001). No
significant effect of MSE was found for CorvisST and ORA metrics.
When assessing the groups separately, no significant (p>0.05)
correlation was found between corneal biomechanics and MSE and
AL (p>0.05) for the myopics. In the non-myopic group a positive
association was identified between AL and CRF (r=0.458, p=0.049),
CH (r=0.457, p=0.049) and A1L (r=0.456, p=0.013) whilst AL and
HC were found to be negatively correlated (r=-0.487, p=0.036)
Conclusions: The study demonstrates significant correspondence
between corneal biomechanics parameters derived from CorvisST
and ORA and AL in non-myopics. The results have interesting
implications on the role of corneal biomechanics in MSE
development. Further investigation into the relationship between
biometric and corneal biomechanical properties in keratoconus,
refractive surgery and juvenile myopia is required.
Commercial Relationships: Daniela Oehring, None; Christine
Purslow, None; Phillip J. Buckhurst, None; Hetal Buckhurst,
None
Support: -
Program Number: 1104 Poster Board Number: D0006
Presentation Time: 3:15 PM–5:00 PM
Biomechanical Evaluation of Response to Treatment with Human
Decorin Core Protein in Ex-Vivo Human and Porcine Corneas
Cynthia J. Roberts1, 2, Kimberly M. Metzler2, 1, Ashraf M. Mahmoud1,
2
, Jun Liu2, 1. 1Ophthalmology, The Ohio State University, Columbus,
OH; 2Biomedical Engineering, The Ohio State University, Columbus,
OH.
Purpose: To investigate changes in corneal biomechanical responses
after crosslinking with decorin core protein. Decorin is a small,
naturally occurring proteoglycan that bridges collagen fibrils,
organizing and stabilizing lamellar collagen architecture.
Methods: A paired eye study design was utilized to investigate
corneal biomechanical changes in 5 human donor pairs (10 eyes)
and in 4 porcine pairs (8 eyes) after one random eye was treated
(tx) with human decorin core protein (Galacorin), and the untreated
fellow eye served as control (c). Epithelium remained intact in all
eyes. An eye cup was used for instillation of pretreatment (45-60
sec), followed by the penetration enhancer (45-60sec), followed
immediately by decorin core protein (45-60sec) with rinsing in
between the last 2 steps. Total treatment time was less than 4 minutes
per eye. Human eyes were secured in a custom tripod mount and
dynamic Scheimpflug deformation analysis was performed using the
CorVis ST at 15, 20, 30, 40, and 50mmHg of intraocular pressure
(IOP). Elastic modulus (E) of the cornea was calculated at each
pressure level in the human eyes, using equations of applanation
and parameters derived from Scheimpflug images. ANOVA was
performed with independent variables of treatment and IOP. Porcine
corneas were investigated using uniaxial tensile testing with a
Rheometrics Systems Analyzer. Paired t tests were then performed.
Results: One human eye pair was excluded based on initial
pachymetry greater than 850mm. ANOVA of the included 4 pairs
demonstrated a significant treatment effect (p < 0.05) in deformation
amplitude, 1st applanation velocity, initial curvature, and pachymetry,
with all lower in the Tx group, consistent with stiffening and
crosslinking. E demonstrated a significant treatment effect with a
higher E in the Tx group. A significant IOP effect was present in most
deformation parameters, as well as E, and the interaction term was
not significant in any parameter. In porcine eye pairs, secant modulus
at both 5% (tx: 1.71± 1.20MPa; c: .85±.62MPa) and 6% (tx: 2.30
±1.33MPa; c: 1.33±.88MPa) strain was significantly higher in the
treated than the untreated corneas (p < 0.05).
Conclusions: Treatment with decorin core protein appeared to
produce higher modulus and stiffer biomechanical behavior in both
human and porcine corneas. This result will be confirmed in future
studies with a larger sample size.
Commercial Relationships: Cynthia J. Roberts, Carl Zeiss
Meditec (F), Euclid Systems Corporation (R), Oculus Optikgeräte
GmbH (C), Ziemer Ophthalmic Systems AG (C); Kimberly M.
Metzler, None; Ashraf M. Mahmoud, None; Jun Liu, None
Support: Euclid Systems Corporation supplied pre-treatment,
penetration enhancer and Galacorin. The Central Ohio Lions
Eye Bank supplied human cadaver eyes. The Ohio Lions Eye
Research Foundation sponsored K. Metzler with the Norbert Peiker
Fellowship.
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Program Number: 1105 Poster Board Number: D0007
Presentation Time: 3:15 PM–5:00 PM
Quantification of corneal biomechanical properties by optical
coherence elastography and a Lamb wave model
Zhaolong Han1, Salavat R. Aglyamov2, Jiasong Li1, Manmohan
Singh1, Shang Wang3, Srilatha Vantipalli4, Chen Wu1, Chih-hao
Liu1, Michael D. Twa5, Kirill Larin1. 1Department of Biomedical
Engineering, University of Houston, Houston, TX; 2Department
of Biomedical Engineering, University of Texas at Austin, Austin,
TX; 3Department of Molecular Physiology and Biophysics,
Baylor College of Medicine, Houston, TX; 4College of Optometry,
University of Houston, Houston, Houston, TX; 5School of Optometry,
University of Alabama, Birmingham, AL.
Purpose: To quantitatively assesse the corneal viscoelasticity by
using optical coherence elastography (OCE) and a Lamb wave
model.
Methods: Air-pulse OCE experiments were conducted on porcine
corneas to obtain the elastic displacement distributions which
behaved as an elastic wave. Phase velocities of the air-pulse induced
elastic waves were extracted by spectral analysis and used for
calculating the Young’s moduli of the samples using the RayleighLamb frequency equation (RLFE). For cornea, the RLFE was
modified to consider the effect of the aqueous humor. Experiments
were performed on 2% agar phantoms (n=3) and then applied to
porcine corneas (n=3) in situ.
Results: Validation experiments were performed on 2% agar
phantoms (Figure a) and compared with uniaxial compressional tests
(Figure b), which demonstrated the accuracy and feasibility of the
RLFE method to reconstruct sample’s mechanical properties. Figure
c demonstrates results from RLFE application to process OCE data
from porcine corneas: the Young’s moduli were estimated to be ~60
kPa with a shear viscosity ~0.33 Pas.
Conclusions: OCE combining RLFE is a promising method for
noninvasive quantification of the corneal biomechanical properties
and may potentially be useful for clinical ophthalmological
applications.
Commercial Relationships: Zhaolong Han, None; Salavat R.
Aglyamov, None; Jiasong Li, None; Manmohan Singh, None;
Shang Wang, None; Srilatha Vantipalli, None; Chen Wu, None;
Chih-hao Liu, None; Michael D. Twa, None; Kirill Larin, None
Program Number: 1106 Poster Board Number: D0008
Presentation Time: 3:15 PM–5:00 PM
A reduced whole eye model to estimate in vivo biomechanical
properties of the human cornea
Mathew Kurian Kummelil1, Rohit Shetty1, Abhijit Sinha Roy2.
1
Cataract and Refractive surgery, Narayana Nethralaya, Bangalore,
India, Bangalore, India; 2Imaging and Biomechanics, Narayana
Nethralaya, Bangalore, India.
Purpose: To develop a reduced whole eye model for inverse
estimation of corneal biomechanical properties
Methods: Figure 1 shows a cross-section of the model. The corneal
limbus was supported by a parallel network of spring (Kz, Kx) and
dashpot (μ) to account for globe, muscles and fat viscoelasticity.
The cornea itself was modeled as a fiber dependent, hyperelastic
and incompressible material. Depth dependent properties were
incorporated to model shear resistance (Petsche et al., 2013).
Corneal deformation from Corvis-ST (OCULUS Optikgerate Gmbh,
Germany) was used in the inverse finite element (iFE) method.
Transient air-puff pressure and a constant intraocular pressure (IOP)
were applied as loads. 10 eyes of 10 normal subjects were measured.
The optimized function was defined as the difference between the
displacement of the anterior edge of the cornea estimated by iFE
and obtained after image processing of Corvis-ST images. The iFE
was solved using Abaqus v.6.12 (Simulia Inc., USA) and custom
python scripting. Further IOP was varied from a normal of 15 mmHg
to 13 and 17 mmHg to assess sensitivity of property parameters to
measured IOP.
Results: Figure 2 shows the apical rise of the corneas vs. simulated
increase in pressure applied to the posterior surface using the
estimated biomechanical properties. The non-linear response of
the cornea was evident and the regression was excellent (R2=0.98).
Figure 3 shows the regressed data for IOP=13, 15 and 17 mmHg
for all the 10 corneas averaged together for each IOP. The average
difference in estimated apical rise was ~5% at 15±2 mmHg. The
mean biomechanical properties of the cellular matrix were 73±22.8
kPa and 4.81±9.97MPa at IOP=15 mmHg. Similarly, the mean
properties of collagen network were 0.39±0.05 kPa and 308±76 at
IOP=15 mmHg.
Conclusions: A novel reduced whole eye model was developed
which significantly reduced the computation time from the previous
whole eye model developed by the authors. The model also
incorporated depth dependent shear properties and demonstrated its
application to estimate in vivo properties.
Validation experiments were performed on 2% agar phantoms (Figure
a) and compared with uniaxial compressional tests (Figure b). Figure
c demonstrates results for porcine corneas: the Young’s moduli were
estimated to be ~60 kPa with a shear viscosity ~0.33 Pas.
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Figure 1 shows a cross-section of the model
Figure 2 shows the apical rise of the corneas vs. simulated increase
in pressure applied to the posterior surface using the estimated
biomechanical properties
Figure 3 shows the regressed data for IOP=13, 15 and 17 mmHg for
all the 10 corneas averaged together for each IOP
Commercial Relationships: Mathew Kurian Kummelil, None;
Rohit Shetty, None; Abhijit Sinha Roy, Avedro (C), Carl Zeiss (C),
Cleveland Clinic Cole Eye Institute (P), Topcon (C)
Program Number: 1107 Poster Board Number: D0009
Presentation Time: 3:15 PM–5:00 PM
Sensitivity analysis of corneal biomechanical and optical behavior
to material and geometrical parameters
Mengchen Xu1, 4, Ashutosh Richhariya2, Amy L. Lerner1, 3, Geunyoung
Yoon4, 3. 1Department of Mechanical Engineering, University of
Rochester, Rochester, NY; 2L V Prasad Eye Institute, Kallam Anji
Reddy Campus, Hyderabad, India; 3Department of Biomedical
Engineering, University of Rochester, Rochester, NY; 4Flaum Eye
Institute, University of Rochester, Rochester, NY.
Purpose: To quantify the relative contribution of different material
and geometrical parameters to apical displacement and optical
aberrations using finite element method and a statistical approach.
Methods: A 3D anisotropic corneal model (Pandolfi, 2006)
with collagen fibril distribution was generated in FEM software
(ABAQUS). The sensitivity analyses were performed in two groups
of parameters (1) geometrical parameters: central and peripheral
corneal thickness, apical rise (H) and base diameter (2Ri), (2) radius
of curvature (R) and material parameters: matrix stiffness (C10), fiber
dispersion (k) denoting the degree of anisotropy, fiber stiffness and
nonlinearity. Ranges of the parameters were chosen from previously
reported data. Outcome measures included apical displacement and
changes in refractive power and spherical aberration (SA) calculated
for 6 mm corneal diameter using an optical ray-tracing software at
multiple intraocular pressures (IOP). Sixteen combinations of the
parameters in each group were designed based on Taguchi style 16TC
Factorial Array (Funkenbusch, 2004). The relative contribution of
each factor to the variance in results was represented by percentage
of total sum of squares (%TSS) and quantified through ANOM and
ANOVA analyses.
Results: Among geometrical parameters, 2Ri influenced apical
displacement most (85.6%TSS) while H was the most important
factor influencing refractive power change (90.4%TSS). Change
in SA was sensitive to both 2Ri and H (37.1 and 57%TSS). In the
second group, k, R and C10 were found to be significantly important
(P<0.01) for apical displacement (80.9%TSS total at 20mmHg IOP).
The significance of k was increased with higher IOP, demonstrating
that fiber dispersion dominated corneal behavior. For optical
behavior, k was the most contributing factor. Varying the degree
of anisotropy due to fiber dispersion from highly oriented to fully
isotropic induced positive SA up to 0.78mm and myopic refractive
power up to 9.9D at 20mmHg IOP. In addition, the interactions of k
with R or C10 also had a significant impact.
Conclusions: Apical rise and base diameter were the two critical
geometrical parameters while fiber dispersion was the most important
material parameter contributing to corneal biomechanical and
optical behavior. These parameters need to be well characterized in
individualized cornea modeling in order to reliably predict surgical
outcomes.
Commercial Relationships: Mengchen Xu, None; Ashutosh
Richhariya, None; Amy L. Lerner, None; Geunyoung Yoon, None
Support: NIH EY014999
Program Number: 1108 Poster Board Number: D0010
Presentation Time: 3:15 PM–5:00 PM
Depth-Dependent Mechanical Properties of the Human Cornea
under Compression
Stephen R. Sloan1, Manuel A. Ramirez Garcia1, Yousuf Khalifa2,
Mark R. Buckley1. 1Biomedical Engineering, University of Rochester,
Pittsford, NY; 2Ophthalmology, Emory University, Atlanta, GA.
Purpose: Characterize the depth-dependent compressive modulus of
central and peripheral human corneas.
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Methods: Unpaired central (n=3) and peripheral (n=3) corneal
buttons 3 mm in diameter were punched from donor human corneas,
then stained in acridine orange (a nuclear dye) to enable straintracking. Specimens were subjected to a stress relaxation test in an
Optisol-GS bath with a microscope-mounted mechanical testing
device (TDIS; Sloan et al., IOVS, 2014) under fluorescence imaging.
A loading rate of 1 um/sec was applied until a peak force of 2.9
N was reached, then the specimens were allowed to relax for 30
minutes.
Two-dimensional digital image correlation software (Jones, Exp.
Mech., 2014) was utilized to calculate the location-dependent
Lagrangian compressive strain. Force measurements at the
equilibrium state (taken to be at the 30 minute mark) were divided by
the cross-sectional area to calculate stress. Compressive modulus was
calculated by dividing stress over strain.
Results: In general, the compressive modulus varied continuously
with depth for both locations and was highest at d/T ~ 0.6, where d
is depth from the anterior surface and T is the tissue thickness. In the
central specimens, a peak compressive modulus of 66 +/- 11 kPa was
found at 60% depth, while the peripheral specimens exhibited a peak
compressive modulus of 55 kPa at 40% depth. At the equilibrium
state, central specimens measured a relaxation thickness of 472 +/- 14
um, while peripheral specimens were 569 +/- 44 um (mean +/- SEM).
Conclusions: Compared to our previously reported corneal shear
modulus profiles that peaked at d/T ~ 0.25, the compressive modulus
peaks substantially closer to the central stroma. These differences
likely reflect distinct structural components of the cornea that
contribute to different modes of mechanical loading.
Compressive Modulus as a function of normalized thickness. Mean
+/- SEM
Commercial Relationships: Stephen R. Sloan, None; Manuel A.
Ramirez Garcia, None; Yousuf Khalifa, None; Mark R. Buckley,
None
Program Number: 1109 Poster Board Number: D0011
Presentation Time: 3:15 PM–5:00 PM
A computational model for collagen-swelling interaction in the in
vivo human cornea
Xi Cheng, Steven J. Petsche, Peter M. Pinsky. Mechanical
Engineering, Stanford University, Stanford, CA.
Purpose: The mechanical behavior and stability of the in vivo cornea
depends on the 3-D organization of stromal lamellae, on the stromal
hydration, and on the interaction between collagen and swelling
forces. A computational biomechanical model for the in vivo cornea,
based on the full 3-D lamella organization and osmotic pressure-
based swelling, is used to investigate: (i) the role of the specific
collagen architecture in corneal biomechanical behavior, including
depth-dependent lamella inclination and interweaving, and (ii)
collagen-swelling interaction in normal and diseased cornea.
Methods: A continuum mechanics-based 3-D model of corneal
behavior has been developed with two principal modeling inputs:
(i) the elasticity of the stroma, and (ii) the swelling behavior. The
elasticity is based on averaging with lamella orientation distributions
at every point in the cornea, and where the orientation distributions
are derived from a synthesis of X-ray diffraction data and second
harmonic-generated image processing. The swelling behavior is
modeled using equilibrium thermodynamics for osmotic pressure
and accounting for active endothelial ion transport which modifies
stromal ionic concentrations. The coupled models are embedded in
a general 3-D finite element framework and used to simulate corneal
biomechanical performance in the normal and swollen state.
Results: Depth-dependence of lamella inclination was found to
significantly affect mechanical and in vivo swelling behavior. Shear
stiffness is predicted to be greater in the anterior cornea, which
was confirmed by direct experimental measurement. Modeling of
swollen corneas (Fuch’s dystrophy) predicts predominant swelling
in the posterior stroma and the role of lamella inclination is clarified
by synthetically varying inclination. Adapted to ex vivo conditions,
the model accurately predicts swelling pressure experimental
measurements.
Conclusions: The model quantifies both lamella-lamella and lamellaswelling structural interactions and predicts a relatively rigid anterior
stromal region. In vivo swelling simulations reproduce observed
primary swelling in the posterior stroma and little change in anterior
surface curvature. The model can predict swelling due to reduction in
active endothelial ion transport. The proposed model is a significant
improvement over existing pure elasticity approaches which cannot
address swelling.
Commercial Relationships: Xi Cheng, None; Steven J. Petsche,
None; Peter M. Pinsky, None
Support: Stanford Bio-X Interdisciplinary Research Initiative II
Program Number: 1110 Poster Board Number: D0012
Presentation Time: 3:15 PM–5:00 PM
BIOMECHANICAL COMPARISON OF CONTRALATERAL
FLAP-BASED AND NO-FLAP FEMTOSECOND LENTICULE
EXTRACTION PROCEDURES USING INVERSE FINITE
ELEMENT ANALYSIS
Ibrahim Seven1, Ali Vahdati1, Cynthia J. Roberts3, Iben B. Pedersen2,
Jesper Hjortdal2, William J. Dupps1. 1Ophthalmic Research,
Cleveland Clinic Cole Eye Institute, Cleveland, OH; 2Aarhus
University Hospital, Aarhus, Denmark; 3The Ohio State University,
Columbus, OH.
Purpose: No-flap lenticule extraction procedure has been introduced
in order to conserve anterior stromal collagen fibers (RELEX SMILE
Carl Zeiss Meditec, Germany). Prior studies using clinical corneal
stiffness measurement devices were limited to differentiate the
biomechanical impact of this procedure comparing to flap based
procedures. This contralateral study aims at predicting the amount of
weakening in collagen fibril elasticity induced by flap-based versus
no flap lenticule extraction methods.
Methods: Patient specific tomography data were meshed using a
custom meshing software consisting epithelium, flap/cap, wound and
residual stromal bed. A hyperelastic, anisotropic, incompressible and
depth dependent material formulation was utilized for the stroma.
Inverse FE analyses were performed using Abaqus 6.11 and Matlab
7.8.0 with 15mmHg intraocular pressure followed by a forward
analysis using 30mmHg IOP to better demonstrate the mechanical
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
impact of each procedure. Two cases, one myopic and one myopic
astigmatism,who received flap-based and no-flap treatments contralaterally were simulated with their clinical treatment settings.
Percentage weakening in the fiber stiffness within the flap region
compared to the no-flap procedure was found by preforming inverse
finite element (FE) study.
Results: Flap based procedure demonstrated 68%, 71% surgically
induced weakening within flap region for patient1 and patient2
respectively. Lower stress and deformation within the residual
stromal bed were noted in the no-flap procedures as opposed to
the flap-based procedures. Simulated refractive outcomes closely
matched the 6month clinical follow-up topographies.
Conclusions: Based on the results of this study, the no-flap procedure
demonstrated higher biomechanical stability following the surgery
as opposed to the flap-based procedure when the same preoperative
material properties were assigned to each contralateral eye.
Surgically induced deformation within residual stromal bed from a
single case. Comparing two procedures at two IOP levels
Surgically induced von-mises stresses within residual stromal bed
from a single case. Comparing two procedures at two IOP levels
Commercial Relationships: Ibrahim Seven, Optoquest (C); Ali
Vahdati, None; Cynthia J. Roberts, Zeiss (C), Zeiss (F); Iben B.
Pedersen, None; Jesper Hjortdal, Zeiss (C); William J. Dupps,
Cleveland Clinic Innovations (P), Zeiss (F)
Support: NIH/NEI R01 EY023381
Program Number: 1111 Poster Board Number: D0013
Presentation Time: 3:15 PM–5:00 PM
Computational Modeling of Unilateral Ectasia after LASIK and
PRK
William J. Dupps1, 2, Ali Vahdati1, Naveen Mysore1, Ibrahim Seven1,
Ronald R. Krueger1, J. Bradley Randleman3. 1Cole Eye Institute,
Cleveland Clinic, Cleveland, OH; 2Biomedical Engineering,
Lerner Research Institute, Cleveland Clinic, Cleveland, OH;
3
Ophthalmology, Emory University, Atlanta, GA.
Purpose: A priori prediction of post-refractive surgery ectasia risk
remains a challenge. Current clinical screening paradigms rely on
incomplete corneal shape characterizations and surrogate surgical risk
factors. We present the first patient-specific computational analyses
of clinically documented post-PRK and post-LASIK ectasia cases
and assess differences in load-induced stress/strain in affected and
unaffected eyes.
Methods: Preoperative and postoperative tomography data from
ectatic and unaffected contralateral eyes were imported into custom
finite element meshing software. Epithelium, flap, wound and
residual stromal bed (RSB) layers were each defined in the LASIK
models. The PRK model consisted only of epithelium and RSB
layers. Stress/strain distributions were obtained using an iterative
method. Munnerlyn ablation algorithms were implemented in
simulations. The cornea was modeled as a fiber-reinforced material
with homogenous solid matrix. At each integration point within
the model, splay of fibers was modeled and angularly integrated.
Each fiber was represented by a 3D helical spring in order to
capture crimping behavior of collagen fibrils. In addition to actual
preop, actual postop and simulated postop simulations, additional
simulations modeled focal reductions in fiber or matrix modulus. All
simulations were performed with 15mmHg and 30 mmHg loads.
Results: In the eye that developed post-LASIK ectasia, maximum
principal strain was 10% higher and more asymmetrically distributed
than the stable eye. Simulated LASIK procedures closely matched
actual postop geometries and produced 10% higher von Mises
stresses in the ectatic eye with a more asymmetric, eccentric
distribution than the stable eye. For the PRK case, similar but
smaller differences in strains and von Mises stresses were observed
in the ectatic eye with shifts in von Mises stress toward the inferiortemporal cornea where the ectatic region manifested clinically.
Similar shifts were observed in models based on actual postoperative
geometry. In both cases, when corneal shear modulus was reduced,
the cornea thinned slightly and the steep feature shifted peripherally.
Conclusions: Structural simulations using patient-specific geometry
and a microstructurally motivated fiber-reinforced model reveal
potential disease-predisposing differences in case-specific mechanical
behavior that may be useful for prediction of post-refractive surgery
ectasia.
Commercial Relationships: William J. Dupps, Cleveland Clinic/
OptoQuest (P); Ali Vahdati, None; Naveen Mysore, None; Ibrahim
Seven, Cleveland Clinic/OptoQuest (C); Ronald R. Krueger, Alcon
(C), Cleveland Clinic/OptoQuest (C); J. Bradley Randleman,
Cleveland Clinic/OptoQuest (C)
Support: NIH Grant R01 EY023381, Innovation Platform Award
from the State of Ohio Third Frontier Commission, and Unrestricted
Grant from Research to Prevent Blindness. WJD is a recipient of a
Research to Prevent Blindness Career Development Award.
Program Number: 1112 Poster Board Number: D0014
Presentation Time: 3:15 PM–5:00 PM
Interlamellar cohesion after collagenase type II exposure in
rabbit cornea
XIAOMING YAN1, JING QIAO1, Wenjing Song1, Yun Tang1, Haili
Li1, Bei Rong1, Songlin Yang1, Yaqi Yin2, Yuan Wu1. 1Department of
Ophthalmology, Peking University First Hospital; Key Laboratory of
Vision Loss and Restoration, Ministry of Education., Beijing, China;
2
Institute of mechanics, Chinese Academy of Sciences; the State Key
Laboratory of Nonlinear Mechanics., Beijing, China.
Purpose: Collagenase could be considered as a method for
generating animal model of keratoconus. The authors aimed to
evaluate the impact of collagenase on the interlamellar cohesive force
of rabbit corneas.
Methods: 20 post mortem New Zealand white rabbit corneas were
divided into 4 groups: group 1(15 mg/ml collagenase type II with
15% dextran, N=5), group 2(10 mg/ml collagenase type II with
15% dextran, N=5),group 3(5 mg/ml collagenase type II with 15%
dextran, N=5) and group 4(the control group,15% dextran, N=5).
After removing epithelium and measuring the corneal thickness,
9*4mm corneal strips were incised and interlamellar cohesive force at
50% depth of stroma was measured with a microcomputer-controlled
biomaterial testing machine.
Results: The mean interlamellar cohesive force of group 1group
2,group 3 and group 4 was 0.225 N/mm,0.217 N/mm,0.199 N/
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
mm,and 0.211 N/mm respectively; without statistically significant
differences. Light microscopy showed stromal tissue became less
tight after collagenase exposure.
Conclusions: Collagenase exposure does not decrease the
interlamellar cohesive force in rabbit corneas, indicating that there
is no significant effect of collagenase on interlamellar cohesion.
Histopathology revealed less tight stroma after collagenase exposure
due to its collagen digestion effect.
Commercial Relationships: XIAOMING YAN, None; JING
QIAO, None; Wenjing Song, None; Yun Tang, None; Haili Li,
None; Bei Rong, None; Songlin Yang, None; Yaqi Yin, None; Yuan
Wu, None
Support: National Natural Science Foundation of China (Grant
No.11372011 ), Beijing Natural Science Foundation(Grant No.
7142159 )
Program Number: 1113 Poster Board Number: D0015
Presentation Time: 3:15 PM–5:00 PM
A pilot study of creating keratoconus model by collagenase type
II
JING QIAO1, XIAOMING YAN1, Wenjing Song1, Yun Tang1, Bei
Rong1, Haili Li1, Songlin Yang1, Yaqi Yin2, Yuan Wu1. 1Department of
Ophthalmology, Peking University First Hospital; Key Laboratory of
Vision Loss and Restoration, Ministry of Education, Beijing, China;
2
Institute of mechanics, Chinese Academy of Sciences; the State Key
Laboratory of Nonlinear Mechanics, Beijing, China.
Purpose: To set up an experimental animal model of keratoconus
using collagenase type II and evaluate corneal curvature changes.
Methods: 20 mortem New Zealand white rabbit corneas were
divided into 4 groups: group 1(15 mg/ml collagenase type II with
15% dextran, N=5), group 2(10 mg/ml collagenase type II with
15% dextran, N=5), group 3(5 mg/ml collagenase type II with 15%
dextran, N=5) and group 4(the control group,15% dextran, N=5).
After epithelial debridement, corneas were mounted and pressured
on artificial anterior chambers,then different kinds of solution was
applied to corneas for 1 hour. Corneal curvature was measured before
and after collagenase exposure at different intraocular pressure
levels(15mmHg, 30mmHg,45mmHg). The results were analyzed
statistically.
Results: After exposure, changes of Kmean in group 1,group 2,group
3 and group 4 were 6.33±4.05D, 0.93±1.13D, 0.67±1.66D and
-0.26±0.77D respectively at 15mmHg; 5.36±2.39D, 1.49±1.70D,
1.37±2.07D and -0.77±1.11D respectively at 30mmHg; 7.29±3.39D,
2.41±2.37D, 1.47±2.63D and -0.56±1.35D respectively at
45mmHg. Compared to group 4, a statistically significant increase
in Kmean across all the intraocular pressure levels was seen in
group 1 (p<0.05).However, group 2, group3 and group 4 were not
significantly different from group 4(p0.05).
Conclusions: 15 mg/ml collagenase type II could induce significant
increase in corneal curvature, which might be considered as a method
of building the rabbit model of keratoconus.
Commercial Relationships: JING QIAO, None; XIAOMING
YAN, None; Wenjing Song, None; Yun Tang, None; Bei Rong,
None; Haili Li, None; Songlin Yang, None; Yaqi Yin, None; Yuan
Wu, None
Support: National Natural Science Foundation of China (Grant
No.11372011 )Beijing Natural Science Foundation (Grant
No.7142159)
Program Number: 1114 Poster Board Number: D0016
Presentation Time: 3:15 PM–5:00 PM
Synthetic media for replacement of serum based conventional
organ culture corneal preservation system
Mohit Parekh1, 3, Gianni Salvalaio1, Stefano Ferrari1, Alessandro
Ruzza1, Marie-Claude Amoureux2, Denis Fortier2, Diego Ponzin1.
1
International Center for Ocular Physiopathology, The Veneto
Eye Bank Foundation, Zelarino, Italy; 2Eurobio, Paris, France;
3
Department of Molecular Medicine, University of Padova, Padova,
Italy.
Purpose: To evaluate the efficacy of a new synthetic medium
(Cornea Syn, Eurobio, France) and compare it with conventional
organ culture medium (Cornea Max, Eurobio, France).
Methods: Cornea Syn is Iscove based, serum free and completed
with recombinant factors needed for maintaining cornea healthy in
organ culture. Seven pairs of human donor corneas were evaluated
using Cornea Syn against the traditional serum based Cornea Max.
Each cornea from the same donor was preserved in Cornea Cold or
Cornea Prep II for 48 hours at RT [phase I], transferred and preserved
in Cornea Syn or Cornea Max for 28 days at 31oC [phase II] followed
by preservation in Cornea Trans or Cornea Jet for 4 days at RT [phase
III]. Parameters such as thickness, transparency, viable endothelial
cell density (VECD), morphology and overall quality were used to
determine the quality of the cornea. Trypan blue for cell mortality;
Lactic acid production in the media; Alizarin red for hexagonality;
ZO-1, p63 and alpha SMA immunostaining for tight junctions, limbal
and smooth muscle actin in the stroma respectively on histological
sections; Hematoxylin Eosin staining for corneal integrity and TdT
dNTP kit for cell apoptosis, were used for analytical study.
Results: Thickness, transparency and overall quality showed
statistical significance (p<0.05) showing better results with Cornea
Syn at phase I however, none of the other parameters showed
any significance at any stage. Cornea Syn showed statistically
significantly lower (p<0.05) production of lactic acid as compared
to Cornea Max however, no statistical significance was observed
in other phases. Alizarin red showed partial preservation of
hexagonality as the morphology deteriorated to some extent in both
series. Immunostaining showed expression of tight junctions of the
endothelium, preservation of the limbal region of the epithelium and
muscle fibres in the stroma. Hematoxylin Eosin staining showed
presence of all the corneal layers. No apoptosis was observed in any
preserved corneas.
Conclusions: Cornea Synthetic series is comparable to the
conventional serum based media which helps to preserve the corneal
integrity and metabolism active. Cornea Syn is a safe and reliable
media for preservation of human donor corneal tissues at 31oC and
has an advantage of having no animal or animal derived components.
Commercial Relationships: Mohit Parekh, None; Gianni
Salvalaio, None; Stefano Ferrari, None; Alessandro Ruzza, None;
Marie-Claude Amoureux, None; Denis Fortier, None; Diego
Ponzin, None
Program Number: 1115 Poster Board Number: D0017
Presentation Time: 3:15 PM–5:00 PM
Keratoprosthesis decentration results in degradation in image
quality
Amanda Tang1, Xiaoyong Fu2, Rony Sayegh1. 1Ophthalmology, Case
Western Reserve University/University Hospitals, Cleveland, OH;
2
Engineering, Case Western Reserve University, Cleveland, OH.
Purpose: Recent reports have focused on methods to improve
centration of the Boston keratoprosthesis (KPro) during surgery.
However, the optical effects of decentration and consequently tilting
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
of the device are unknown. We investigate these effects on image
quality using a computer model.
Methods: A model of the PMMA KPro was created in Zemax (Focus
Software Inc, San Diego, Calif). Computerized ray-tracing technique
was used to simulate the image projected on the retina in an eye with
a perfectly centered KPro, and eyes with various degrees of KPro
decentration and corresponding tilt. The degree of tilt was calculated
based on the radius of curvature of KPro backplate of 8.0 mm. The
spot diagrams for a wavelength of 587.6 nm and a pupil diameter of
3.0 mm were derived and the simulated images on the macula are
presented.
Results: The perfectly centered KPro (0 mm decentration) had a
tight point spread function which resulted in the formation of a
high quality image. Decentration of the KPro by 0.8, 1.5, and 2.3
mm (backplate abutting the angle) with a corresponding respective
tilt of 5.6, 11.4, and 17.0 degrees was simulated. Spot diagrams
demonstrating the change in image quality of a point object across
the retina showed increased astigmatism and peripheral distortions of
the retinal image with increasing decentration and tilt. This became
significant with a decentration of 1.5 mm and beyond. Simulated
images illustrate the resultant distortions. The addition of asphericity
to the anterior lens surface of the KPro resulted in improved off-axis
image quality while maintaining good potential visual acuity.
Conclusions: Low amounts of decentration and tilt of the KPro are of
little consequence on image quality projected on the retina, however,
distortion of the projected image occurs with higher amounts of
decentration. Our results illustrate the importance of attempting good
centration of the device during surgery. Alternatively, aspherically
optimizing the lens surface during manufacturing would result in
dampening of the distortion effect. The model also confirms our
previous observation that tilting of the KPro result in astigmatism on
refraction.
Commercial Relationships: Amanda Tang, None; Xiaoyong Fu,
None; Rony Sayegh, None
Program Number: 1116 Poster Board Number: D0018
Presentation Time: 3:15 PM–5:00 PM
Anatomical and visual outcomes after Boston Keratoprosthesis
type 1 in chemical burns: the Santo Domingo experience
Borja Salvador Culla1, Linette Arzeno2, Paraskevi E. Kolovou1,
Santiago Martínez2, Claes H. Dohlman1, Miguel Ángel López2.
1
Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard
Medical School, Boston, MA; 2Hospital Elías Santana, Santo
Domingo, Dominican Republic.
Purpose: To describe the visual outcomes, anatomical retention
and postoperative complications of patients who underwent type 1
Boston Keratoprosthesis (B-Kpro) after ocular chemical burns in the
Dominican Republic.
Methods: A retrospective review of case series including 42 eyes of
36 patients with ocular chemical burn who underwent B-Kpro type
1 implantation at Hospital Elías Santana in Santo Domingo between
September 2006 and October 2014 was conducted. Visual acuity,
anatomical retention and the rate of postoperative complications were
evaluated.
Results: The mean age of patients was 40.86 years (25-62); 34 were
male while 2 were female. The causative agent was ammonia in 21
cases, hydrochloric acid in 6 cases, hydraulic fluid in 1 case, and the
agent was unknown in 14 cases. The mean follow-up time was 38.45
months (median 30; range 2-98). Best corrected mean visual acuity
(LogMAR) was 2.12 (+/-0.9) at first visit, 2.44 (+/-0.64) immediately
prior to B-Kpro implantation, 0.71 (+/-0.61) at 1 month, 0.69 (+/0.75) at 6 months, 0.95 (+/-0.98) at 1 year, 1.27 (+/-1.30) at 2 years,
1.53 (+/-1.43) at 3 years, 1.25 (+/-1.41) at 4 years, and 1.32 (+/-1.44)
at 5 years. Anatomical retention of the first implanted B-Kpro was
achieved in 90.5% of the eyes after 1 year and 78.6.3% at 2 years.
The most frequent postoperative complication was the development
of a posterior capsule opacification (26%), followed by glaucoma
(19%) and corneal melting (17%). Other complications included
hypotony (5%), extrusion (5%), retroprosthetic membrane (5%),
epiretinal membrane (3%), retinal detachment (3%), hemovitreous
(3%), endophthalmitis (1%), and Ahmed valve abscess (1%).
Conclusions: Our study demonstrates an excellent retention rate of
the B-Kpro type 1 in chemical burns after 2 years, with a maintained
improvement of the best corrected visual acuity in the majority of
patients. Because these eyes are severely damaged, it is important to
follow up closely these patients after B-Kpro implantation to prevent
and address promptly any vision-threatening complication.
Commercial Relationships: Borja Salvador Culla, Boston
Keratoprosthesis, Massachusetts Eye and Ear Infirmary (F); Linette
Arzeno, None; Paraskevi E. Kolovou, Boston Keratoprosthesis,
Massachusetts Eye and Ear Infirmary (F); Santiago Martínez, None;
Claes H. Dohlman, Boston Keratoprosthesis, Massachusetts Eye and
Ear Infirmary (F); Miguel Ángel López, None
Program Number: 1117 Poster Board Number: D0019
Presentation Time: 3:15 PM–5:00 PM
Long Term Outcomes of Boston KPro Type I implantation in
Aniridia Associated Keratopathy
Jose De la Cruz, Maria S. Cortina, Samantha L. Williamson,
Kimberly Hsu. Ophthalmology, University of Illinois Eye and Ear
Infirmary, Chicago, IL.
Purpose: To evaluate the long term outcomes of aniridic patients
undergoing keratoprosthesis implantation in an Interdisciplinary
artificial cornea center.
Methods: Retrospective, Single Center, Case Series
Results: Eighteen Aniridic KPRO Type I (17 patients, 1 bilateral).
Age: Mean 44, (SD 18): Female: Male, 13:4. KLAL prior to KPRO:
11 eyes. Survival Rate (days): Mean: 1635 days, SD: 1132 days
(Min 269 days, Max 3156 days). Type of Surgery: Aphakic KPRO
10 (55%), Pseudophakic KPRO 5 (28%). Combined KPRO/PPV/
Glaucoma Tube Shunt 3 (17%). Follow up: Mean 990 days, SD 692
days.Visual Acuity Pre OP (18 eyes): 20/400 (2) 11%, 20/800 (1)
5%, CF (7) 39%, HM (7) 39%, LP (1) 5%. Last Follow up BCVA:
20/60 (2) 12.5%, 20/100 (3) 18.7%, 20/250 (3) 18.7%, 20/300 (1)
6%, 20/400 (2) 12.5%, CF (1) 6%, HM (1) 6%, LP (1) 6%, NLP
(2) 12.5%.•VA 20/250 or better 55%. VA 20/300 or better 61%.
VA 20/400 or worse 39%. Worst than pre-op 16 % (3) (one due to
trauma, one due to intraop complication choroidal heme, one due to
hypotony). Complications: Retroprosthetic Membranes (RPM) (12
eyes) 67%,. Period of Time of Appearance of RPM: Mean: 293 days
(SD: 511 days, Min 35 days, Max 1855 days. Sterile keratolysis/
extrusion (3 eyes) 25%. Time to sterile keratolysis/extrusion: Mean:
169 days, (SD: 30 days, Min: 150 days, Max: 204 days). Extrusion
preserved baseline VA after replacement (20/100, 20/250, 20/100).
Conclusions: Long term implantation of Boston KPRO provides for
a viable alterrnative for visual rehabilitation in aniridia associated
keratopathy. Even in cases of extrusions the eyes preserved adequate
vision after re-implantation comparesd to pre-op.
Commercial Relationships: Jose De la Cruz, None; Maria S.
Cortina, None; Samantha L. Williamson, None; Kimberly Hsu,
None
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Program Number: 1118 Poster Board Number: D0020
Presentation Time: 3:15 PM–5:00 PM
Pars Plana Vitrectomy and Silicone Oil insertion Protect Against
Endophthalmitis in Patients with Boston Type 1 Keratoprosthesis
Mohamed Abou Shousha, Zachary Schmitz, Joshua Abernathy, Ross
Chod, Zachary Bodnar, Rocio Bentivegna, Sean Edelstein, Levent
Akduman. Ophthalmology, Saint Louis University, St. Louis, MO.
Purpose: To evaluate visual outcomes and postoperative
complication rates in eyes with Boston type 1 keratoprosthesis
combined with pars plana vitrectomy and silicone oil insertion
(KPro+PPV+SOI) as compared to eyes receiving Boston type 1
keratoprosthesis (KPro) alone.
Methods: Retrospective case control study of 24 eyes with Boston
type 1 keratoprosthesis. Ten of these eyes had hypotony and/
or retinal detachment in addition to corneal pathology, and thus
received KPro implantation combined with pars plana vitrectomy
and silicone oil insertion. Outcome measures included best-corrected
visual acuity (BCVA) and rates of post-operative complications
including endophthalmitis, KPro extrusion, retinal detachment, newly
developed glaucoma and retroprosthetic membrane (RPM) recorded
at 1, 3, 6 and 12 months follow-up visits
Results: In the KPro+PPV+SOI group, no eyes had developed
endophthalmitis by the 12 month follow-up visit. On the other hand,
5 eyes in the uncombined KPro group developed endophthalmitis
(P<0.05). Four of these 5 eyes had vitreous taps with positive
bacterial cultures. Other complications included Kpro extrusion
(1 in each group), retinal detachment (1 in each group), newly
developed glaucoma (2 in the KPro group) and RPM (6 in KPro and
4 in KPro+PPV+SOI group). The KPro group had better average
preoperative and 1st month postoperative BCVA as compared to those
of the Kpro+PPV+SIO group (1/200 vs. HM; P=0.01 and 20/300 vs.
3/200; P=0.03, respectively). No statistically significant difference in
BCVA was noted in subsequent follow-up visits.
Conclusions: Boston type 1 Keratoprosthesis combined with pars
plana vitrectomy and silicone oil insertion in eyes with corneal
pathology as well as hypotony and/or retinal detachment is a safe and
effective procedure for visual rehabilitation. Furthermore, pars plana
vitrectomy and silicone oil insertion may have a protective effect
against the development of postoperative endophthalmitis in eyes
receiving the Boston Type 1 Keratoprosthesis.
Commercial Relationships: Mohamed Abou Shousha, None;
Zachary Schmitz, None; Joshua Abernathy, None; Ross Chod,
None; Zachary Bodnar, None; Rocio Bentivegna, None; Sean
Edelstein, None; Levent Akduman, None
Program Number: 1119 Poster Board Number: D0021
Presentation Time: 3:15 PM–5:00 PM
Boston type I Keratoprosthesis: surgical indications, outcomes,
retention rate and complications in a single-(international)-center
study
Alejandro Navas1, Juan Carlos Serna-Ojeda1, Jasbeth Ledesma
Gil2, Arturo J. Ramirez-Miranda1, Enrique O. Graue1. 1Cornea
and Refractive Surgery, Institute of Ophtalmology “Conde de
Valenciana”, Mexico City, Mexico; 2Glaucoma, Institute of
Ophtalmology “Conde de Valenciana”, Mexico City, Mexico.
Purpose: To evaluate the preoperative indications, postoperative
complications, retention rate and surgical outcomes of patients with
Boston Type I (formerly Dohlman type I) Keratoprosthesis in an
international center.
Methods: An observational and retrospective study was performed
with review of the medical records of patients who underwent
Boston Type 1 Keratoprosthesis (KPro) implantation at Instituto
de Oftalmología Conde de Valenciana (an ophthalmologic
reference center) in Mexico City, Mexico. The variables analyzed
included surgical indication, initial and final visual acuity, previous
keratoplasties, postoperative complications and retention rate.
Results: 22 eyes of 21 patients with a median age of 49.5 years
(range 24 - 90 years), median follow-up after keratoprostheses of
14 months (range 3 to 124 months). Preoperative visual acuity was
worst than 20/100 in all cases. Indications for surgery included:
corneal dystrophies in 4 patients (19.0%), ocular burns (2 patients,
9.5%), aniridia (2 patients, 9.5%), bullous keratopathy (3 patients,
14.2%), Stevens-Johnson syndrome (2 patients, 9.5%), severe ocular
rosacea (1 patient, 4.7%), among others. One patient with binocular
keratoprostheses had rheumatoid arthritis with severe ocular surface
disease. In 16 eyes (76.1%), previous penetrating keratoplasties
were attempted with failure. Four patients were treated with
keratoprosthesis assisted with intraprosthetic amniotic membrane.
Postoperative complications included retroprosthetic membranes
in 4 patients (19.0%), retrolental membranes in 2 (9.5%), retinal
detachments in 2 (9.5%) and endophthalmitis in 2 (9.5%). Of the
22 keratoprosthesis implanted, 4 have been removed, obtaining a
retention rate of 81% during follow-up; in 2 cases keratoprostheses
re-placement was performed and 2 cases presented endophthalmitis,
one requiring evisceration. 14 eyes had a final visual acuity equal or
better than 20/400 (with a median of 20/60).
Conclusions: Indications for Boston Type I keratoprosthesis are
varied, and usually reserved for very complex cases with previous
failed penetrating keratoplasties as a common characteristic.
Postoperative complication and retention rates remained similar to
other series. Boston type I keratoprosthesis implantation is increasing
abroad, it is important to report the outcomes from different venues
around the world.
Commercial Relationships: Alejandro Navas, None; Juan Carlos
Serna-Ojeda, None; Jasbeth Ledesma Gil, None; Arturo J.
Ramirez-Miranda, None; Enrique O. Graue, None
Program Number: 1120 Poster Board Number: D0022
Presentation Time: 3:15 PM–5:00 PM
Evaluation of anterior chamber angle by anterior segment
optical coherence tomography in different back plate models of
implanted Boston type 1 keratoprosthesis
Kimberly Hsu1, Joann Kang1, Norma Allemann1, 2, Jose De la Cruz1,
Maria S. Cortina1. 1University of Illinois at Chicago, Chicago, IL;
2
Federal University of Sao Paulo, Sao Paulo, Brazil.
Purpose: To compare the anterior chamber angle (ACA) and
presence of peripheral anterior synechiae (PAS) in patients with
implanted Boston Type 1 keratoprosthesis including 7.0 mm and 8.5
mm PMMA and 8.5 mm titanium back plate models.
Methods: A retrospective study of patients who received a Boston
Type 1 keratoprosthesis from 2009 – 2014 was conducted. The type
of implanted back plate was determined from the operative report.
Anterior segment optical coherence tomography images taken at the
last postoperative visit were reviewed and ACA measurements and
number of clock hours of PAS were recorded.
Results: 29 patients with a 7.0 mm PMMA back plate, 12 patients
with an 8.5 mm PMMA back plate, and 7 patients with an 8.5 mm
titanium back plate were included in the study with a mean follow up
of 16.4, 27.5, and 2.1 months, respectively. Average ACA was 4.7 in
the 7.0 PMMA group, 2.7 in the 8.0 mm PMMA group, and 17.2 in
the titanium group. The difference in ACA between the titanium and
the 7.0 mm PMMA group was statistically significant (p = 0.005),
and there was a trend towards significance comparing the titanium
to the 8.0 mm PMMA group (p = 0.01). There was no difference
between the two PMMA back plate sizes. The average clock hours
of PAS were 6.6, 6.0, and 6.0 for the 7.0 mm PMMA group, 8.5
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
mm PMMA group, and titanium group, respectively. There were no
statistically significant differences in clock hours of PAS between
groups.
Conclusions: Our results suggest that patients with titanium back
plates may be able to maintain their angle better than patients with
PMMA back plates but PAS formation appeared to be similar to all
groups. It has been suggested that Boston Type 1 keratoprosthesis
titanium back plates incite less post-operative inflammatory response
than PMMA back plates, which may in part explain our findings.
However, longer follow up is needed to determine the clinical
relevance of different back plate materials and sizes.
Commercial Relationships: Kimberly Hsu, None; Joann Kang,
None; Norma Allemann, None; Jose De la Cruz, None; Maria S.
Cortina, None
Program Number: 1121 Poster Board Number: D0023
Presentation Time: 3:15 PM–5:00 PM
Glare Reduction Strategies for Keratoprosthesis
Musa Abdelaziz2, Claes H. Dohlman1, Rony R. Sayegh2.
1
Ophthalmology, Massachusetts Eye & Ear Infirmary, Boston,
MA; 2Ophthalmology, University Hospitals/Case Western Reserve
University, Cleveland, OH.
Purpose: Significant glare is frequently reported by patients after
Boston keratoprosthesis (KPro) surgery. An opaque contact lens is
helpful but potential movement of the lens limits its usefulness in
many patients. We explore the effect of various modifications to the
KPro assembly on glare.
Methods: A custom made optical bench setup was used. A point light
source (LED) of adjustable intensity and a collimator lens system
were used for illumination. A sand-blasted scattering Boston scleral
lens was drilled to allow insertion of a type 1 KPro front plate. A
CCD camera on a rotating arm captured the image of the point source
and the surrounding scatter at different angles. The type 1 KPro used
was designed for an aphakic eye (focal length, 14.8 mm in air). Pointspread function (PSF) curves with corresponding area under the curve
(AUC) were derived using Matlab.
Results: A tight PSF curve was obtained with the KPro surrounded
by an opaque iris (control, AUC 3.3). A wider PSF curve (more glare)
was noted with the use of a PMMA back plate (AUC 5.3) compared
with the newer titanium back plate (AUC 4.4). The addition of a
+2.00D acrylic intraocular lens placed behind the KPro with titanium
back plate did not increase scatter (AUC 4.2). The use of a modified
titanium locking-ring that is 6mm in diameter eliminated scatter and
resulted in a PSF similar to the control (AUC 3.3). Maximal scatter
was noted with KPro front plate inserted in the sand-blasted scleral
lens (AUC 11.3).
Conclusions: The newer titanium back plate provides better glare
protection compared to its older PMMA counterpart. There is no
difference in measured glare between pseudophakic and aphakic
KPros. Modification of the locking ring design may be an effective
strategy to reduce glare.
Commercial Relationships: Musa Abdelaziz, None; Claes H.
Dohlman, None; Rony R. Sayegh, None
Program Number: 1122 Poster Board Number: D0024
Presentation Time: 3:15 PM–5:00 PM
Hyperopic refractive error in eyes with Boston Type 1
keratoprosthesis and silicone oil
Zachary M. Bodnar, Mohamed Abou Shousha, Ross Chod, Levent
Akduman. Ophthalmology, St. Louis University, St. Louis, MO.
Purpose:
To examine the refractive outcomes of Boston Type 1
keratoprosthesis in aphakic eyes with silicone oil.
Methods:
Five patients with a history of pars plana vitrectomy and Boston
Type 1 keratoprosthesis (KPro) with clear media and reliable
post-operative manifest and/or auto-refraction were identified. The
spherical equivalent of the measured post-operative refractive errors
were compared to predicted refractive errors as determined by a
mathematical model based on known physical parameters of the KPro
and media and the axial lengths of the operative eyes.
Results:
Aphakic patients with Boston Type1 keratoprostheses had a mean
hyperopic refractive error of +12.45 diopters as compared to a
predicted mean error of +4.19 diopters (p = 0.04).
Conclusions:
Silicone oil significantly affects the post-operative refractive
error of patients with Boston Type 1 keratoprostheses. Power
calculations may need to be adjusted for aphakic patients undergoing
keratoprosthesis surgery with permanent silicone oil tamponade.
Commercial Relationships: Zachary M. Bodnar, None; Mohamed
Abou Shousha, None; Ross Chod, None; Levent Akduman, None
Program Number: 1123 Poster Board Number: D0025
Presentation Time: 3:15 PM–5:00 PM
Longitudinal Assessment of Boston Type 1 Keratoprosthesis/
Cornea Interface by Anterior Segment-OCT Allows Detection
and Monitoring of Corneal Tissue Melts
Rodrigo Müller, Elise Taniguchi, Andrea Cruzat, Bernardo M.
Cavalcanti, Claes H. Dohlman, Pedram Hamrah. Massachusetts Eye
and Ear Infirmary, Boston, MA.
Purpose: To prospectively evaluate the presence and alterations
of potential spaces and areas of tissue melting(gaps) in the donor
cornea, under the Boston Type 1 Keratoprosthesis (K-Pro1) front
plate, as well as corneal epithelial tissue lipping over the edge of
the front plate(epi-lip), using anterior segment-optical coherence
tomography(AS-OCT).
Methods: AS-OCT (RTVue OCT, Optovue Inc., Fremont, CA)
was performed at the device-donor corneal interface in all 4
quadrants(qds) around the K-Pro1 at two time points (mean followup time of 1.3±0.98years). Presence, alterations, and size of gaps
between the front plate and the donor cornea, as well as epi-lips, were
evaluated at baseline and follow-up.
Results: Forty-two eyes of 36 patients were assessed(mean of
4.8±2.9years after surgery), and 25 eyes of 23 patients were analyzed
at follow-up. From 154 OCT qds imaged at the first visit, 56(36.3%)
revealed a gap under the front plate. The gap area was on average
12.7±33.3mm2. Among the qds with gaps, 19(34%) revealed no epilip, while among the qds without gaps, only 3(3.0%) had no epi-lip
(p<0.0001). In addition, the epi-lip area was significantly smaller
among the qds with gaps compared to qds without gaps(22.1±23.8
and 49.5±49.8mm2,p<0.0001). There was a significant correlation
between the gap area and epi-lip area (r=-0.33,p<0.0001). On
follow-up examination, 60% of the qds remained without gaps(from
20 eyes), 17% remained stable or regressed(from 12 eyes) and 23%
progressed(from 12 eyes), with one eye advancing to extrusion and
two eyes having had a prior history of extrusion in the previous
K-Pro. Among those qds with gaps that progressed, 30% had no
epi-lip during the first visit while, among those qds that remained
stable or regressed, 18% had no epi-lip. Finally, among those qds
that remained without gaps, only 3% had no epi-lip(p<0.0001).
The relative risk for progression of gaps at the follow-up visits was
1.7(p=0.07); however, it was 3.2 in qds with no epi-lips during the
first visit, compared to qds with epi-lip (p=0.0005).
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Conclusions: Patients with K-Pro Type 1 may demonstrate gaps
under the front plate. The epi-lip may confer protection against
development of gaps. While corneas in patients without gaps remain
stable, presentation of gaps can progress and could demonstrate a risk
factors for corneal melting, requiring closer follow-up.
Commercial Relationships: Rodrigo Müller, None; Elise
Taniguchi, None; Andrea Cruzat, None; Bernardo M. Cavalcanti,
None; Claes H. Dohlman, None; Pedram Hamrah, None
Support: K-Pro Foundation, NIH K08-EY020575, Falk Medical
Research Trust
Program Number: 1124 Poster Board Number: D0026
Presentation Time: 3:15 PM–5:00 PM
Biocompatibility of Graphene as Candidate Biomaterial for
Synthetic Keratoprosthesis Skirt
Jodhbir S. Mehta1, 2, Brianna Thompson2, Aris konstantopoulos1,
Gwen Goh1, Melina Setiawan1, Donald Tan1, K Khor2. 1Cornea
Refractive Tissue Engineering, SNEC / SERI, Singapore, Singapore;
2
Nanyang Technological University, Singapore, Singapore.
Purpose: Osteo-odonto keratoprosthesis (OOKP) is one of the
most successful forms of keratoprosthesis surgery for end-stage
corneal and ocular surface disease. However, in edentulous patients
a synthetic OOKP maybe required. Titanium has been shown to be
a possible candidate material for a skirt of a synOOKP. However,
Titanium is brittle and a stronger material e.g graphene maybe more
appropriate. The aim of this study was to assess the biocompatibility
of graphene in the cornea.
Methods: Test materials included pristine graphene film,
graphene foam and titanium discs (TiO2). Human corneal stroma
fibroblast attachment was analyzed by immunostaining of focal
adhesion proteins. Cell proliferation rates were assessed by
3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide
(MTT) assay and Click Edu Assay at various time points. Fibroblast
attachment on the pores of the graphene foam was confirmed
by scanning electronic microscopy whilst cytokine absorption
was analyzed by enzyme-linked immunosorbent assay (ELISA).
Graphene films were implanted into rabbit corneal stroma pockets
and monitored by slit lamp, Anterior Segment Optical Coherence
Tomography (AS-OCT) scanning and in vivo confocal microscopy
for 3 weeks. Tissue inflammatory responses were further analyzed by
Hematoxylin and Eosin (H&E) staining.
Results: Pristine graphene demonstrated good biointegration with
human corneal stromal fibroblasts in terms of cell adhesion and
proliferation. Graphene displayed better cell viability at the 7 days
compared with Ti. The expression levels of IL-6 and IL-8 were
significantly reduced when cells were seeded on graphene foam as
compared to those seeded on Ti and graphene film. Rabbit cornea
tissue showed no detectable inflammation clinically and minimal
inflammatory response was observed by histological analysis.
Conclusions: Graphene displays excellent biocompatibility with
corneal stroma cells and corneal tissue. Hence, graphene has the
potential to be developed as a tissue engineering material suitable for
use as a synthetic OOKP skirt.
Commercial Relationships: Jodhbir S. Mehta, None; Brianna
Thompson, None; Aris konstantopoulos, None; Gwen Goh, None;
Melina Setiawan, None; Donald Tan, None; K Khor, None
Support: NMRC TCR EyeSite
Program Number: 1125 Poster Board Number: D0027
Presentation Time: 3:15 PM–5:00 PM
Surface quality assessment of explanted keratoprostheses using
confocal and scanning electron microscopy
Jean-Marie A. Parel1, 4, Heather A. Durkee1, Patricia L. Blackwelder6,
Darlene Miller5, Antonio Bermudez2, Kavitha Sivaraman3, Florence
Cabot3, Mariela C. Aguilar1, Victor L. Perez3, Guillermo Amescua3.
1
Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, Miami, FL; 2Ocular
Pathology, Bascom Palmer Eye Institute, University of Miami Miller
School of Medicine, Miami, FL; 3Ophthalmology, Bascom Palmer
Eye Institute, University of Miami Miller School of Medicine,
Miami, FL; 4Brien Holden Vision Institute, UNSW, Sydney, NSW,
Australia; 5Ocular Microbiology Laboratory, Bascom Palmer Eye
Institute, University of Miami Miller School of Medicine, Miami, FL;
6
University of Miami Center for Advanced Microscopy (UMCAM)
and Marine Geosciences (RSMAS), University of Miami, Coral
Gables, FL.
Purpose: To evaluate the effects of the irregular surfaces of Boston
Type I keratoprostheses after explanation using confocal and
scanning electron microscopy.
Methods: Failed Boston Type I Keratoprostheses (KPro) were
collected from patients undergoing KPro explantation or exchange
at Bascom Palmer Eye Institute, Miami, FL, USA. In the operating
room, the KPro samples were placed in a container with balanced
salt solution immediately after removal. Fluorescent confocal
microscopy was performed on the fresh, un-fixed KPro samples to
visualize the microbial adherence and cellular growth. A live/dead
green/red fluorescent stain was used along with a Leica 5PS confocal
microscope. Images were taken across the entire anterior and
posterior surfaces of the KPro samples to characterize the complete
KPro surface. The optical surfaces of the KPro were imaged with
bright field illumination of the confocal microscopy. After confocal
microscopy, the KPro sample is fixed in 10% formalin, immersed in
PBS buffer, dehydrated in a graded series of ethanol, dried in HMDS,
and sputter-coated with Palladium for scanning electron microscopy
(SEM). Images of the anterior and posterior surfaces of the KPro
were obtained using SEM at multiple magnifications (30x–5000x).
Results: Confocal microscopy and SEM images showed rough
surfaces on all regions of the keratoprostheses. The confocal
microcopy revealed cellular growth in areas of more irregularities.
The high magnification SEM images showed many bacteria and
biofilm colonies attached to the KPros. In one case, the patient also
had an intraocular lens (IOL) which was analyzed as was the KPro
to relate surface features to microbial adherence. The IOL had super
polished surfaces with almost no microbial adherence.
Conclusions: Dual imaging approaches in this ongoing study enabled
an accurate evaluation of the failed keratoprostheses, and thus better
elucidated the mechanisms that lead to their explantation.
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Confocal microscopy images of external and internal KPro surfaces
shows cellular activity and biofilm
SEM images of external and internal KPro surfaces. The
retroprosthetic membrane traverses through the holes extends to the
anterior surface of the backplate.
Commercial Relationships: Jean-Marie A. Parel, None; Heather
A. Durkee, None; Patricia L. Blackwelder, None; Darlene Miller,
None; Antonio Bermudez, None; Kavitha Sivaraman, None;
Florence Cabot, None; Mariela C. Aguilar, None; Victor L. Perez,
None; Guillermo Amescua, None
Support: USAMRMC Department of Defense W81XWH-09-1-0674,
Florida Lions Eye Bank, Drs. KR Olsen and ME Hildebrandt, NIH
P30EY1481 (Center Grant), Research to Prevent Blindness, Henri
and Flore Lesieur Foundation (JMP). Scientific support was provided
by: Drs Eduardo Alfonso, Sander Dubovy, Yoh Sawatari, Jose de la
Cruz, Nidhi Relhan Batra, Shawn P. Kelly and Gabe Gaidosh.
Program Number: 1126 Poster Board Number: D0028
Presentation Time: 3:15 PM–5:00 PM
Role of titanium surface topography in regulation of corneal cell
growth, patterning, and matrix deposition
Chengxin Zhou1, 2, James Chodosh3, 2, Claes H. Dohlman3, 2,
Eleftherios I. Paschalis1, 2. 1Schepens Eye Research Institute –
Massachusetts Eye and Ear, Boston, MA; 2Harvard Medical School,
Boston, MA; 3Massachusetts Eye and Ear, Boston, MA.
Purpose: Medigrade titanium (Ti) is used in Boston Keratorposthesis
(BK-Pro) backplates. However, the interaction between corneal cells
and different Ti surface topographies (ST) has never been studied.
This study was undertaken to assess the effect of Ti-ST in human
corneal cells.
Methods: Equally hydrophilic Ti disks with different STs, ranging
from Grade 0 (0.175 RMS; smoothest) to Grade 3 (4.413 RMS;
roughest) were placed on the bottom of 24-wells and cultured
with human corneal/limbal epithelial (HCLE), stromal fibroblasts
(HCFs), endothelial cells and HeLa cells (n=3; for each cell line).
Cell cytotoxicity and proliferation assays were performed at Day
2, 3, and 5. HCFs were also cultured for 6 weeks in serum media +
ascorbic acid, w/wt TGFβ1, and tested for collagen deposition, cell
morphology and α-smooth muscle actin (αSMA) expression.
Results: None of the Ti Grades showed cell cytotoxicity (p>0.05,
one-way ANOVA). However, Grade 2 and 3 caused significant
inhibition of HCLE and HCF cell proliferation at Day 3 and 5
compared to Grade 0. At 6 weeks of HCF culture in serum media, all
Ti Grades had equal cell densities and did not induce myofibroblast
transformation. Yet Grade 3 had significantly less collagen deposition
compared to Grade 0 (p<0.05). Grade 0 provided HCFs better cell
adhesion, remarkable directionality in cell alignment and had parallel
aligned, fibrillar collagen meshwork, while Grade 3 had randomly
aligned cells and collagen deposits.
Addition of TGFβ1 in HCF culture caused marked myofibroblast
transformation and more collagen-V secretion in all Grades.
Transformed HCFs on Grade 3 had higher αSMA expression,
less collagen deposition and randomly oriented collagen fibrils as
compared to those on Grade 0 which had parallel aligned collagen
fibrils.
Conclusions: To our knowledge, this is the first study suggesting that
Ti-ST plays an important regulatory role in corneal cell phenotype.
The effect is tissue-dependent, varying across different corneal
stratums, with epithelium being more impacted. Contrary to the
established paradigm in Orthopedics, smooth Ti surface better
facilitates corneal cell proliferation, matrix deposition, and reduces
αSMA expression under TGFβ1 stimulation as compared to rough
Ti surface. These results suggest that BK-Pro Ti may benefit from
tissue-targeted surface modification that promotes desired biological
responses in the cornea.
Commercial Relationships: Chengxin Zhou, None; James
Chodosh, None; Claes H. Dohlman, None; Eleftherios I. Paschalis,
None
Support: Boston Keratoprosthesis Research Fund, Massachusetts
Eye and Ear, Boston, MA
Program Number: 1127 Poster Board Number: D0029
Presentation Time: 3:15 PM–5:00 PM
Using replacement methods to live animal testing for evaluating
the toxicity/fixation potential of candidate therapeutic tissue
cross-linking agents
Su-Young Kim1, Brendan Roach2, Natasha Babar1, Anna Takaoka1,
Clark Hung2, Stephen Trokel1, David C. Paik1. 1Ophthalmology,
Columbia University Medical Center, New York, NY; 2Biomedical
Engineering, Columbia University, New York, NY.
Purpose: As the field of corneal cross-linking (CXL) and therapeutic
tissue cross-linking (TXL) in other tissues (such as sclera) moves
forward, understanding the relationship or balance between the
ability to induce mechanical tissue changes and killing cells
becomes relevant. This could be particularly important as we pursue
refinements in either chemical or photochemical approaches. Thus,
the present study was undertaken in order to develop a potential
replacement method for live animal testing when evaluating such
approaches.
Methods: Organ cultured bovine cartilage explants and fresh
cadaveric rabbit corneas in an ex vivo corneal crosslinking simulation
set up was used. The tissue was exposed to the formaldehyde
releasing agent (FAR) diazolidinyl urea (DAU) under continuous
exposure (22, 220, 2200 uM) in low glucose explant growth medium
at pH 7.2 for 3 to 7 days for cartilage; and for 30min (1.8mM
epithelium-off and 8.9mM epithelium-on) at pH 8.5 for cornea. As a
comparison, the same ex vivo system was used to conduct riboflavinmediated photochemical CXL of cornea. Post-exposure, the tissue
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
viability was assessed using a LIVE/DEAD Viability/Cytotoxicity Kit
(Life Technologies) and imaged on an inverted confocal microscope.
Thermal transition temperature (Tm) was determined by differential
scanning calorimetry.
Results: Concentration dependent effects in cell viability were noted.
Lower concentrations and shorter exposure times were associated
with lower cell toxicity. In the cartilage, DAU was cytotoxic at
2200uM, showed a time dependent effect at 220uM, and was well
tolerated at 22uM. In corneal tissue that showed shifts in Tm by
DSC, we were able to visualize both live and dead cells in both the
endothelial and stromal regions.
Conclusions: These methods could be very helpful in refining our
current approaches to tissue cross-linking therapy and are a possible
“replacement” method to live animal testing. These methods will be
further developed for the purpose of evaluating the “toxicity/fixation
balance” of therapeutic tissue cross-linking approaches.
Commercial Relationships: Su-Young Kim, None; Brendan
Roach, None; Natasha Babar, None; Anna Takaoka, None; Clark
Hung, None; Stephen Trokel, None; David C. Paik, None
Program Number: 1128 Poster Board Number: D0030
Presentation Time: 3:15 PM–5:00 PM
The role of Scheimpflug imaging derived parameters in the
progression of keratoconus: a systematic review and retrospective
study
Wishal Ramdas1, Unal Mutlu3, Bart Van Dooren1, 2. 1Ophthalmology,
ErasmusMC, Rotterdam, Netherlands; 2Ophthalmology, Amphia
Hospital, Breda, Netherlands; 3Epidemiology, ErasmusMC,
Rotterdam, Netherlands.
Purpose: To investigate corneal topographic differences between
keratoconic and control eyes and the long-term changes of corneal
topographic parameters in untreated keratoconic eyes, as assessed
with the Pentacam.
Methods: In this retrospective case-control study, we first performed
an systematic review to find eligible topographic parameters and
indices for keratoconus progression. The eligible parameters and
indices were compared in untreated keratoconic eyes and control
eyes. Next, the discriminative ability of the tested variables was
analyzed. Furthermore, the difference between baseline and followup was assessed. All patients underwent at least one Pentacam scan.
Results: A total of 310 untreated eyes with follow-up data were
identified and compared with 361 control eyes. Most topographic
parameters and indices differed significantly between both groups
(p<0.001). Receiver operating curve analysis revealed the highest
area under curve values for Kmax, Rmin, ISV, IVA, KI and IHD
(0.876, 0.871, 0.870, 0.874, 0.885, 0.884 and 0.887, respectively).
Parameters that significantly changed over a mean follow-up of 24.17
months were Kmax, Rmin, K2 B, Kmean B, Rm B, Rh B, chamber
volume, ACD and corneal volume.
Conclusions: Our data indicates that the maximum keratometry and
the steepest radius of front and back corneal surface are the most
eligible parameters to follow keratoconus progression on long-term.
Index of surface variance (ISV) and index of height decentration
(IHD) may be the most sensitive for diagnosis. Also standard
notations of parameters should be considered in future research.
Commercial Relationships: Wishal Ramdas, None; Unal Mutlu,
None; Bart Van Dooren, None
Program Number: 1129 Poster Board Number: D0031
Presentation Time: 3:15 PM–5:00 PM
Novel in vitro model for human corneal diabetes
Shrestha Priyadarsini1, Akhee Sarker-Nag1, Dimitrios Karamichos1,
2 1
. Ophthalmology, OUHSC, Dean McGee Eye Institute, Oklahoma
City, OK; 2Cell Biology, OUHSC, Dean McGee Eye Institute,
Oklahoma CIty, OK.
Purpose: Diabetes mellitus is a metabolic disorder that results due to
hyperglycemic condition for a prolonged duration and often leads to
various ophthalmic complications. Cornea is one of the most severely
affected ocular structures with devastating results including vision
impairments, corneal edema, delayed wound healing, and ulcers. In
this study we have developed a novel 3-dimensional in vitro model
using primary human corneal stroma diabetic cells from Type I and
Type II donors. We have identified key signaling pathways involved
in corneal DM defects using our 3D in vitro that mirror what is seen
in vivo.
Methods: Human corneas stromal cells were isolated and cultured
from healthy/no ocular disease (HCF) donors and from Type I
(T1DM) and Type 2 (T2DM) diabetic donors. All cells were cultured
on polycarbonate membranes for 4 week and stimulated with a
stable Vitamin C (VitC) derivative. All constructs were processed for
immunofluorescence, real time PCR, and western blot analysis.
Results: Our data shows significant morphological changes between
HCF and T1DM. T2DM appear similar to HCF with long spindle
shape morphology while T1DM appear bigger, with multiple
processors, and large cytoskeleton. In terms of ECM, both T1DM and
T2DM assembled significant larger amount of ECM when compared
to HCF (~40%; p<0.05). Collagen I was down regulated by at least
2-fold in both T1DM and T2DM, while Collagen III and α-SMA
were only up-regulated in T1DM (15 and 5-fold respectively). IGF-1
and IGF-1R, previously linked to diabetes, were both up regulated in
T2DM. T1DM showed significant up regulation of IGF-1R but not
IGF1.
Conclusions: Overall, we have developed a novel 3D in vitro
model that allows for the study of cellular and ECM interactions,
which may help understand the root problem of the human corneal
diabetes. Diabetes has significant effect on morphological, metabolic,
physiological, and clinical aspects of the cornea. The benefits of
developing an in vitro model are enormous and provide clues for
novel therapeutics to treat diabetes defects in cornea.
Commercial Relationships: Shrestha Priyadarsini, None; Akhee
Sarker-Nag, None; Dimitrios Karamichos, None
Program Number: 1130 Poster Board Number: D0032
Presentation Time: 3:15 PM–5:00 PM
Analysis of corneal biomechanics using ultra high-speed
Scheimpflug imaging to distinguish normal from keratoconic
patients
Riccardo Vinciguerra1, 2, Renato Ambròsio3, Ahmed Elsheikh4,
Bernardo Lopes3, Emanuela Morenghi5, Simone Donati2, Claudio
Azzolini2, Paolo Vinciguerra1. 1Opthalmology, Humanitas Clinical
and Research Center, Milan, Italy; 2Department of Surgical and
Morphological Sciences, University of Insubria, Circolo Hospital,
Varese, Italy; 3Rio de Janeiro Corneal Tomography and Biomechanics
Study Group, Federal University of São Paulo, Rio De Janeiro,
Brazil; 4Ocular Biomechanics Group, School of Engineering,
University of Liverpool, Liverpool, United Kingdom; 5Biostatistics
Unit, Humanitas Clinical and Research Center, Milan, Italy.
Purpose: To evaluate the ability of a high-speed Scheimpflug camera
(Corvis ST,Oculus,Wetzlar,Germany) to distinguish between normal
and keratoconic(kc)eyes,by comparing new corneal deformation
parameters (CDP).
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Methods: Retrospective comparative study including 792 eyes, a
normal group comprised of 587 eyes and 205 keratoconic cases.
Diagnosis was based on clinical examinations, including Placidodisk based corneal topography and rotating Scheimpflug corneal
tomography. Data from the Corvis ST were extracted using research
software including Intraocular pressure (IOP), central corneal
thickness (CCT) and a total of 56 CDP. Additionally, a new IOP
correction (IOPc) algorithm based on Ocular Biomechanics Group of
the University of Liverpool (UK) that includes CDPs, CCT and age.
Logistic regression technique was used to evaluate the discriminant
faculty of each parameter and then receiver operating characteristic
(ROC) curves were calculated. The independent parameter with an
area under the receiver operating characteristic curve (AUC) over 0.7
and a sensibility over 0.75 with a specificity non less than 0.5 were
included in a multivariable logistic regression to combine parameters
in order to provide best possible separation between normal patients
and kc.
Results: Statistically significant differences between kc and normal
eyes were found in all CDPs (p<0.05) except for 10 non significant
CDPs that were excluded. There were 3 CDP with AUC higher
than 0.8. The best individual CDP was ratio between deformation
amplitude and deformation amplitude at 2 mm (DA/DA2) with AUC
of 0.8680.
The CDPs included in the multivariable logistic regression were
second applanation time, first applanation deflection amplitude,
maximum deflection amplitude, slope of deflection amplitude, frame
of second applanation, inverse concave radius, simulated time of
second applanation and DA/DA2. The analysis was also adjusted for
age and IOPc.
The multivariate logistic regression revealed an AUC of 0.9938,
providing a very high predictive accuracy.
Conclusions: Our study demonstrates that Corvis ST is able
to provide data that is able to distinguish between normal and
keratoconic patients with high predictive accuracy by combining
deformation parameters. The integration of CDPs from Corvis ST
and tomographic data is promising to further enhance the screening
accuracy for ectatic diseases.
Commercial Relationships: Riccardo Vinciguerra, None; Renato
Ambròsio, Alcon-Wavelight (C), OCULUS (C); Ahmed Elsheikh,
OCULUS (F); Bernardo Lopes, None; Emanuela Morenghi, None;
Simone Donati, None; Claudio Azzolini, None; Paolo Vinciguerra,
Oculus (C), Schwind (C), SOOFT (C)
Program Number: 1131 Poster Board Number: D0033
Presentation Time: 3:15 PM–5:00 PM
Finite element modeling of metabolic species transport in the
cornea with a hydrogel intrastromal inlay
Peter M. Pinsky1, Keith Holliday2. 1Mechanical Engineering, Stanford
University, Stanford, CA; 2Research, Revision Optics, Inc, Lake
Forest, CA.
Purpose: Intrastromal inlays for refractive correction of presbyopia
are being adopted into clinical practice. An important concern is
the effect of the inlay on the long-term health of the cornea due to
disturbances in the concentration profiles of metabolic species. A 3-D
metabolic model for the cornea is employed to investigate oxygen,
glucose and lactate ion transport in the cornea and to estimate
changes in species concentrations induced by the introduction of a
hydrogel inlay.
Methods: A reaction-diffusion metabolic model, appropriate for
highly oxygen-permeable hydrogel inlays, is used to describe
cellular consumption of oxygen and glucose and production of
lactic acid. A three-layer corneal geometry comprising epithelium,
stroma, and endothelium, is employed with a hydrogel inlay placed
under a lamellar flap. The model is solved numerically by the finite
element method. The accuracy of the metabolic model is assessed
by comparing predicted glucose consumption rates to experimental
measurements for rabbit in vitro. The model is employed to predict
concentration profiles in a cornea containing an inlay made from a
commercially available hydrogel material.
Results: Predicted glucose consumption rate versus glucose
concentration in the normal cornea compared reasonably well with
rabbit measurements and confirm the predictive accuracy of the
model. For a cornea with a hydrogel inlay having a relative inlay
diffusivity of 43.5%, predicted maximum glucose depletion and
lactate ion accumulation occur anterior to the inlay and both are less
than 3%. A sensitivity study on inlay diffusivity showed that glucose
depletion and lactate ion accumulation are insensitive to reductions
in inlay diffusivity until the limit of approximately 20% relative
diffusivity; below this level, glucose and lactate ion concentrations
increase exponentially. For fixed inlay diffusivity, glucose depletion
increases slightly with increasing depth of inlay placement.
Conclusions: The flux of metabolic species is modified by an
inlay, depending on the inlay relative diffusivity. For commercially
available hydrogel materials and a typical inlay design, predicted
changes in species concentrations are small when compared to the
variation of concentrations across the normal cornea. In general,
glucose depletion and lactate ion accumulation are highly sensitive to
inlay diffusivity and somewhat insensitive to inlay depth.
Commercial Relationships: Peter M. Pinsky, Revision Optics, Inc
(C); Keith Holliday, Revision Optics, Inc (E)
Program Number: 1132 Poster Board Number: D0034
Presentation Time: 3:15 PM–5:00 PM
Towards a New Keratoconus Screening Paradigm: Correlating
Known Risk Factors with the Corneal Spatial Thickness Profile
and Biomechanical Properties Obtained from the Ocular
Response Analyzer
Neema Nayeb-Hashemi, John Jesse. Ophthalmology, Loyola
University, Chicago, IL.
Purpose: Keratoconus (KCN) is a problem that affects millions of
individuals worldwide. To this point, there has been no clear way of
determining who is at risk of developing KCN until the changes in
the cornea begin to manifest in the corneal topographic imaging. We
performed a retrospective chart review looking at normal eyes versus
eyes with KCN and compared corneal spatial thickness profiles
(STP), and Ocular Response Analyzer (ORA) data to determine if
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
there was any correlation which may help predict who is at increased
risk of KCN in the future.
Methods: Pentacam data and ORA data collected from 100 normal
and 32 KCN eyes was reviewed. Using the STP, a third order
polynomial best fit was computed using Microsoft Excel. The
coefficients of the best fit curve as well as the ORA` data were then
analyzed using a multivariable and correlational analysis looking for
differences between groups.
Results: In comparing normal eyes to eyes with KCN, STP best
fit coefficients were found to be as follows: the constant was 133.5
points lower for KCN vs normal eyes (p<0.001). Conversely, the
first, second, and third order coefficient was 20.2, 10.3, and 2.53
points greater for the KCN group (p<0.003). Adjusting for corneal
steepness however, the third order coefficient was found to be
insignificant (p>0.07). Using ORA data, it was found that the corneal
resistance factor (CRF) and corneal hysteresis factor (CHF) was 3.2
and 2.2 points lower for the KCN group respectively (p <0.001).
Adjusting for corneal steepness, the differences remained significant.
Correlational analysis determined that only the constant was
significantly correlated with CRF in both KCN and normal eyes.
Conclusions: While initial studies comparing STP between KCN
and normal eyes validated its diagnostic value, little effort has been
spent attempting to quantify the differences in order to determine
whether a screening protocol can be derived from the coefficients of
the best fit. The fact that all the coefficients and the constant were
significantly different may be secondary to the severity of KCN in a
significant portion of the cohort. Future comparisons of early KCN
eyes to normal eyes with similar corneal thicknesses and curvature,
will help elucidate whether the coefficients of the STP can be useful
in predicting individuals at risk for KCN.
Commercial Relationships: Neema Nayeb-Hashemi, None; John
Jesse, None
Program Number: 1133 Poster Board Number: D0035
Presentation Time: 3:15 PM–5:00 PM
Optical Coherence Elastography of the Deep Corneal Stroma
after Rose Bengal Green light Crosslinking in Rabbit Corneas
Srilatha Vantipalli1, Jiasong Li3, Manmohan Singh3, Kirill Larin3,
Michael D. Twa2. 1College of Optometry, University of Houston,
Houston, TX; 2School of Optometry, University of Alabama,
Birmingham, AL; 3Department of Biomedical Engineering,
University of Houston, Houston, TX.
Purpose: There are structural and biochemical differences between
the anterior and posterior corneal stroma. It is not advisable to use
conventional UV-Riboflavin cross-linking in the deep corneal stroma
due to potential UV-induced endothelial cell toxicity. Here we
evaluate the biomechanical effect of Rose Bengal Green Light Cross-
linking (RGX) treatment on the deep corneal stroma measured using
a custom-built optical coherence elastography (OCE) system.
Methods: OCE measurements (three conditions) were made at the
corneal apex in vitro on 4 rabbit eyes: anterior surface after deepithelialization, deep stroma (after trephination to 2/3rd corneal
thickness) and after RGX treatment in the deep stroma. RGX was
performed using 0.1% rose bengal solution for 20 minutes (one drop
every 5 min) and 10 min green light irradiation (565nm, 0.25W/
cm2). Dynamic tissue deformation responses were produced using
a focal micro air pulse stimulator (150mm spot size, 1ms duration,
and 4Pa; 0.03mmHg) and surface deformation was recorded using a
phase-sensitive swept-source optical coherence tomography (OCT)
imaging system. Tissue deformation responses were quantified as
the relaxation rate (recovery from deformation) and shear wavefront
propagation speed. Intraocular pressure was stabilized throughout
testing (10mmHg) using a closed–loop micro infusion syringe pump
control system.
Results: Mean relaxation rate was 1.65 ± 0.4ms-1 and group velocity
at the anterior surface was 1.02 ± 0.21m/s with an average corneal
thickness of 642 ± 19.7mm. Relaxation rate at a depth of 2/3rd corneal
thickness (224 ± 59mm) was greater (18.6%) after RGX treatment
(1.88 ± 0.24ms-1) than in untreated tissue (1.58 ± 0.1ms-1). Group
velocity was also greater (13.2%) post-treatment (1.01 ± 0.1m/s)
than in untreated tissue (0.89 ± 0.07m/s). Faster recovery (higher
relaxation rate) and greater group velocity is consistent with stiffer
material properties.
Conclusions: Higher relaxation rate and faster group velocity
demonstrate an increase in stiffness in the deep cornea with RGX
treatment. This shows promise for future applications in lamellar
keratoplasty and refractive surgery through modification of deep
corneal biomechanical properties.
Commercial Relationships: Srilatha Vantipalli, None; Jiasong Li,
None; Manmohan Singh, None; Kirill Larin, None; Michael D.
Twa, None
Support: R01-EY022362-01
Program Number: 1134 Poster Board Number: D0036
Presentation Time: 3:15 PM–5:00 PM
An investigation into corneal enzymatic resistance following
epithelium-removed, partial epithelium disruption and
epithelium-intact riboflavin/UVA cross-linking procedures
Nada H. Aldahlawi1, 2, Sally Hayes1, David O’Brart3, Keith Meek1.
1
School of Optometry and Vision Sciences, Cardiff University,
Cardiff, United Kingdom; 2Department of Optometry Sciences,
College of Applied Medical Sciences, King Saud University, Riyadh,
Saudi Arabia; 3Department of Ophthalmology, St Thomas Hospital,
Keratoconus Research Institute, London, United Kingdom.
Purpose: Riboflavin/UVA corneal collagen crosslinking therapy has
been shown to successfully halt keratoconus progression by stiffening
the corneal stroma and increasing its resistance to enzymatic
digestion. The aim of this study was to compare the effectiveness of
epithelium-removed, partial epithelial disruption and transepithelial
crosslinking protocols, in terms of their ability increase the resistance
of the cornea to enzymatic digestion.
Methods: Sixty enucleated porcine eyes were examined and
randomly divided into ten groups. Groups 1 and 2 had the corneal
epithelium removed and 0.1 % riboflavin phosphate/20% dextran
eye drops applied for 30 minutes. Groups 3 and 4 had grid pattern
partial epithelial disruption followed by 30 minutes of 0.1 %
riboflavin phosphate eye drops. All other groups were treated with an
intact epithelium. Groups 5 and 6 had 0.25% riboflavin Mediocross
transepithelial (TE) eye drops applied for 30 minutes. Groups 7
and 8 underwent iontophoresis for 5 minutes with 0.1 % riboflavin
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
phosphate eye drops, and groups 9 and 10 underwent iontophoresis
for 10 minutes with 0.25% riboflavin Mediocross TE. Following the
application of riboflavin, groups 2, 4, 6, 8 and 10 were irradiated for
10 minutes with 9 mW UVA light. Daily measurements of corneal
diameter were recorded in order to monitor the rate of enzymatic
digestion.
Results: Resistance to enzymatic digestion was significantly greater
in all cross-linked groups than non-cross-linked groups (p<0.0001).
On average, complete digestion of the corneal buttons occurred by
day 11 ± 0.5 in the non-irradiated groups and by day 25 ± 9.7 in the
cross-linked groups. Epithelium-off cross-linking resulted in a greater
increase in enzymatic resistance than partial epithelial disruption
crosslinking or epithelium-on cross-linking (p<0.0001). The
iontophoresis cross-linking protocol used in Group 10 resulted in a
greater resistance to enzymatic digestion than any of the other partial
epithelial disruption or trans-epithelial crosslinking protocols tested
(Groups 4, 6, 8) (p<0.0001).
Conclusions: Although currently not as effective as epithelium-off
cross-linking, the outcome of trans-epithelial cross-linking may be
significantly improved through the use of higher concentrations of
riboflavin solution and a longer duration of iontophoresis.
Commercial Relationships: Nada H. Aldahlawi, None; Sally
Hayes, None; David O’Brart, None; Keith Meek, None
Support: King Saud University Grant R1269
Program Number: 1135 Poster Board Number: D0037
Presentation Time: 3:15 PM–5:00 PM
Corneal deformation imaging of Rose Bengal-green light
cross-linked rabbit corneas: in vivo vs ex vivo treatments and
measurements
Nandor Bekesi1, Pablo Pérez-Merino1, Lucía Ibares-Frías2, Carmen
Martinez-Garcia2, Irene E. Kochevar3, Susana Marcos1. 1Instituto
de Optica, CSIC, Madrid, Spain; 2Grupo de Técnicas Ópticas de
Diagnóstico, University of Valladolid, Valladolid, Spain; 3Wellman
Center for Photomedicine, Harvard Medical School, Boston, MA.
Purpose: (1) To assess biomechanical changes induced in rabbit
corneas by Rose Bengal green light collagen cross-linking (RB-GCXL), (2) To compare corneal deformation following ex vivo and in
vivo treatments and measurements.
Methods: The effects of RB-G-CXL on air puff corneal deformation
were studied on a total of 20 rabbit eyes. New Zealand white female
rabbits were monolaterally treated with RB-G-CXL in vivo, with
the contralateral eyes as controls. Treatment consisted of deepithelization, application of Rose Bengal photosensitizer (0.1% w/v)
for 2 min, 300 s of green light irradiation, 30 s staining and 300 s
of irradiation. The light source was a solid-state laser (532 nm, 0.25
W/cm2, Gaussian beam profile FWHM=10 mm). The limbus was
masked during the treatment. Corneal deformation was evaluated in
vivo 28 days post-treatment in CXL and control eyes. Measurements
were repeated ex vivo following euthanasia at constant intraocular
pressure (IOP=15 mmHg). Three untreated (contralateral control)
eyes and 14 additional virgin ex vivo eyes were treated ex vivo
24-hours post-mortem, following an identical protocol, and measured
immediately after CXL. Corneal air-puff dynamic deformation was
measured by a Scheimpflug-imaging Corvis ST (Oculus, Germany)
device. Deformation amplitude was taken as a metric for corneal
stiffness.
Results: Average deformation amplitude was 1.55 ± 0.26 mm in
control eyes and 1.56 ± 0.21 mm in CXL eyes in vivo (p=0.9); 1.31
± 0.05 mm in control eyes and 1.13 ± 0.03 mm in vivo-treated CXL
eyes (p=0.005) that were measured ex vivo with constant IOP; 1.40
± 0.19 mm in control eyes before and 1.30 ± 0.25 mm after ex-vivo
CXL (p=0.2), 24-hours post mortem. Statistical differences (p<0.03)
were also found between deformation amplitude measured in vivo
and ex vivo.
Conclusions: Decreased corneal deformation amplitude following
CXL is consistent with increased corneal stiffness, although
statistical differences were only found for ex vivo measurements
under constant IOP. The absence of significant differences measured
in vivo, consistent with clinical findings in patients following
other CXL protocols, suggests a major masking role of IOP. Rose
Bengal green-light CXL appears to be a suitable method to increase
corneal stiffness. However IOP should be incorporated in corneal
biomechanical metrics based on air-puff corneal deformation.
Commercial Relationships: Nandor Bekesi, None; Pablo PérezMerino, None; Lucía Ibares-Frías, None; Carmen MartinezGarcia, None; Irene E. Kochevar, Massachusetts General Hospital
(P); Susana Marcos, None
Support: EU+Madrid FP7/2007-2013 REA grant 291820; FIS201125637; ERC-2011-AdG-294099 and Oculus for access to Corvis
Program Number: 1136 Poster Board Number: D0038
Presentation Time: 3:15 PM–5:00 PM
No additional biomechanical effect of CXL after repeated in vivo
treatment in mice
David Tabibian1, Sabine Kling1, Arthur Hammer1, Olivier Richoz1,
Farhad Hafezi2, 1. 1Ophthalmology, University of Geneva, Geneva,
Switzerland; 2ELZA Institute, Zürich, Switzerland.
Purpose: To analyze and compare corneal biomechanics of single
and multiple corneal cross-linking in the mouse eye.
Methods: The corneas of C57BL/6 mice were divided into in two
groups. In the first group, corneas were cross-linked once (day 1),
in the second group a second CXL was performed at 72 hours (day
4) after the initial procedure (n=3 each). Untreated corneas served
as controls (n=3). Biomechanical measurements were performed at
day 7. The CXL procedure was adapted to the anatomy of the mouse
eye, using 0.27%-riboflavin for 20 minutes and UVA irradiation
(365 nm, 9mW/cm2) for 2:50 minutes in an epi-off procedure. After
irradiation, mice were sacrificed, corneas were excised and mounted
on a customized 2D-flap-holder. The biomechanical measurement
consisted of three parts: (i) pre-conditioning, (ii) stress relaxation
during 120 s and (iii) stress-strain curve until break.
Results: After a relaxation period of 120 seconds, highly significant
(p<0.001) differences in the stress-strain curves were found between
controls and single cross-linked corneas. No significant differences
(p=0.70) were measured between 1x and 2x cross-linked corneas.
The stress remaining after relaxation was 355 ± 25.2 kPa in riboflavin
controls, 457 ± 34.1 kPa in 1x cross-linked corneas and 463 ± 22.2
kPa in 2x cross-linked corneas.
Conclusions: Repeated cross-linking does not further increase
corneal biomechanical stiffness in the mouse cornea in vivo. This
might indicate that the stiffness of the cornea cannot be arbitrarily
augmented over certain levels.
Commercial Relationships: David Tabibian, None; Sabine Kling,
None; Arthur Hammer, None; Olivier Richoz, None; Farhad
Hafezi, None
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
Program Number: 1137 Poster Board Number: D0039
Presentation Time: 3:15 PM–5:00 PM
Biomechanical Efficacy of UV Cross-Linking Protocols in Thin
versus Thick Corneas: The Effect of Oxygen, UV Absorption and
Osmotic Pressure
Sabine Kling1, David Tabibian1, Olivier Richoz1, Arthur Hammer1,
Amar Agarwal3, Soosan Jacob3, Farhad Hafezi4, 2. 1Laboratory for
Ocular Cell Biology, University of Geneva, Geneva, Switzerland;
2
Department of Ophthalmology, University of Southern California,
Los Angeles, CA; 3Dr. Agarwal’s Eye Hospital and Eye Research
Center, Chennai, India; 4ELZA Institute, Zurich, Switzerland.
Purpose: To compare the current clinically used UV corneal crosslinking (CXL) treatment protocols for thin corneas with respect to
oxygen, UV fluence and osmotic pressure.
Methods: Freshly enucleated murine (N=25) and porcine (N=38)
eyes were used to study the effect of corneal thickness in the
CXL treatment. The dependency on oxygen and the amount of
UV absorption were evaluated for various epithelium-off CXL
protocols, including standard CXL, contact lens assisted CXL,
CXL after corneal swelling, contact lens control and riboflavin
control. Treatment parameters were adapted according to the corneal
thickness of the species used. Immediately after CXL, corneas were
subjected to biomechanical testing, including pre-conditioning,
stress-relaxation at 0.6 MPa and stress-strain extensiometry. A twoelement Prony series was fitted to the relaxation curve for viscoelastic
characterization.
Results: Standard CXL was biomechanically most efficient; prior
corneal swelling and CACXL reduced the long-term modulus by
6% and 15-20%, respectively. Oxygen reduction decreased the G∞
modulus by 14-15%, the G0 modulus by 2-5% and increased the G2
modulus by 22-31%. Reducing the amount of absorbed UV-energy
decreased the G∞ modulus by 5-34%, the G0 modulus by 7-29% and
the G2 modulus by 17-20%. The amount of absorbed UV-light was
more important in porcine than in murine corneas.
Conclusions: Thin corneas have a higher oxygen availability, which
potentially increases the efficacy of CXL. Clinical protocols for thin
corneas should be revised to take advantage of this finding.
Commercial Relationships: Sabine Kling, None; David Tabibian,
None; Olivier Richoz, None; Arthur Hammer, None; Amar
Agarwal, None; Soosan Jacob, None; Farhad Hafezi, None
Support: Castier foundation
Program Number: 1138 Poster Board Number: D0040
Presentation Time: 3:15 PM–5:00 PM
3D corneal elasticity mapping in normal and keratoconus
patients
Sebastien Besner2, 1, Giuliano Scarcelli2, 1, roberto pineda3, Seok
H. Yun2, 1, Patricia Kalout3. 1Wellman Center for Photomedicine,
Massachusetts General Hospital, Boston, MA; 2Dermatology,
Harvard Medical School, Boston, MA; 3Department of
Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston, MA.
Purpose: The balance between the cornea mechanical strength and
the intraocular pressure is critical to maintain normal shape. When
disrupted, the local stress can lead to a progressive compensatory
thinning and bulging of the cornea or keratectasia. Although marked
clinical advances have been made in cornea structural imaging,
still no method is available to map elasticity in vivo. In this study,
we present a non-contact method for in vivo mechanical mapping
based on Brillouin scattering and evaluate its diagnostic potential for
keratoconus.
Methods: A 780-nm confocal Brillouin microscope (P=1.5 mW,
rlateral=5 μm, raxial=35 μm) combined with real time eye registration
system was used to acquire 6-mm central cornea elasticity maps in
11 normal and 5 advanced keratoconus patients. Axial scans were
taken at various lateral positions with a depth scanning interval of 30
μm. The Brillouin anterior modulus was computed by averaging the
Brillouin shift value over the anterior portion of the stroma and used
to construct lateral elasticity maps. Correlations between pachymetry/
curvature (Pentacam, Oculus) and Brillouin map were established.
Results: In normal patients, the cornea mechanical strength
decreased with depth and increased toward its periphery. In average,
the central Brillouin shift at 80% depth was ~80 MHz lower in
comparison to the anterior region. Laterally, the Brillouin modulus
increased by 30 MHz. It also increased with age in the range of 20-60
years old (0.7±0.2 MHz/year, p=0.005). When converted into shear
modulus, those relative changes corresponded to a 2.4x decrease in
depth, a 1.5x increase radially, and a 0.8%/year increase with age. In
keratoconus patients, the Brillouin modulus in the cone region was
about 100 MHz lower (2.9x drop in shear modulus) and the lateral
gradient was 3.8x steeper than the normal control. Away from the
cone, the Brillouin modulus was comparable to the normal ones. In
all patients, Brillouin modulus was positively correlated with cornea
thickness and negatively correlated with front sagittal curvature.
Conclusions: Striking differences could be observed between the
normal and keratoconic cornea biomechanics. While normal corneas
presented a gradual increase of the elastic modulus from its center
toward the periphery, strong mechanical focal weakening was
observed in keratoconus cases. Cornea stiffness increased with age,
and may explain the high prevalence of keratoconus in teenage years.
Commercial Relationships: Sebastien Besner, None; Giuliano
Scarcelli, MGH (P); roberto pineda, Amgen (C), Angiotech (C);
Seok H. Yun, MGH (P); Patricia Kalout, None
Support: NIH UL1-RR025758, NIH P41-EB015903, NIH R21EY023043, NIH K25-EB015885, American Society for Laser
Medicine and Surgery, and Human Frontier Science Program
Program Number: 1139 Poster Board Number: D0041
Presentation Time: 3:15 PM–5:00 PM
Determing stromal riboflavin concentrations for epi-off and
epi-on formulations using UPLC (Ultra Performance Liquid
Chromatography)
Arthur Hammer2, Serges Rudaz1, Sylvie Guinchard1, Olivier Richoz2,
David Tabibian2, Sabine Kling2, Farhad Hafezi3, 2. 1School of
Pharmaceutical Sciences, University of Geneva (UNIGE), Geneva,
Switzerland; 2Laboratory for Ocular Cell Biology, University of
Geneva (UNIGE), Geneva, Switzerland; 3ELZA Institute, Zurich,
Switzerland.
Purpose: To investigate on the concentration of different riboflavin
compounds in the corneal stroma after epi-off and epi-on instillation
Methods: Various riboflavin solutions were tested using UPLC
analysis to determine riboflavin and riboflavin phosphate isomers
concentrations. Solutions were either tested as formulation, or after
a 30 minutes in vivo instillation into the stroma of rabbits, followed
by excision of the cornea using a manual trepan (7mm diameter)
and extraction. Untreated corneas served as controls. Prior to in vivo
riboflavin instillation, either an 8 mm abrasion was performed, or
the epithelium was exposed to one drop of tetracaine 1% collyre per
minute for five minutes.
Results: The concentrations of riboflavin and riboflavin phosphate
isomers did not show significant differences for the different
formulations when tested as is. However, when comparing the
concentrations of riboflavin and riboflavin phosphate isomers
between the formulations and their respective corneal concentrations
after 30 minutes of instillation, we observed a decrease of 2 to 3
log units. In particular, we observed an “inversion” between the
riboflavin and riboflavin phosphate isomers concentrations, with
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].
ARVO 2015 Annual Meeting Abstracts
riboflavin 5’monophosphate being the compound with the highest
concentration in the formulations, but the lowest in the cornea, and
the non-phosphated riboflavin being the compound with the lowest
concentration in the formulations, but the highest in the cornea.
Conclusions: Statistical analysis showed no significant differences
between the stromal concentrations of the various riboflavin
compounds using different solutions and epi-on and epi-off protocols.
This lack of significance could be due to the thinner epithelium in the
rabbit cornea when compared to the human cornea, allowing the epion formulations to penetrate the stroma more efficiently.
The observed and unexpected “inversion” of the compound
concentrations from the formulations to the corneas could be
explained by the higher electronegativity of the phosphated isoforms,
hindering stromal penetration. Modification of the riboflavin vs
phosphate isoforms ratio might influence the efficacy of current epioff protocols
Commercial Relationships: Arthur Hammer, None; Serges
Rudaz, None; Sylvie Guinchard, None; Olivier Richoz, Emagine
(P); David Tabibian, None; Sabine Kling, None; Farhad Hafezi,
Emagine (P)
Support: MD PhD fellowship grant from the Swiss National Fund
Program Number: 1140 Poster Board Number: D0042
Presentation Time: 3:15 PM–5:00 PM
Development of a Porcine Eye Model to Assess Application of a
Novel Corneal Shaping Device during Corneal Collagen CrossLinking (CXL)
Angela Zhu1, 2, Eva-Maria Lackner2, Jennifer Elisseeff2, 3, Albert
S. Jun2. 1Case Western Reserve University School of Medicine,
Cleveland Heights, OH; 2Wilmer Eye Institute, Johns Hopkins
Medical Institutions, Baltimore, MD; 3Translational Tissue
Engineering Center, Johns Hopkins Medical Institutions, Baltimore,
MD.
Purpose: Corneal collagen cross-linking (CXL) has great potential
in delaying progression of corneal ectactic disorders, but CXL
alone cannot substantially improve corneal shape abnormalities. We
designed a novel corneal shaping device to be physically applied
during CXL and developed an ex vivo porcine eye model to show that
our device prototype used in conjunction with CXL can alter corneal
curvature to a greater extent than with CXL alone.
Methods: A prototype of the corneal shaping device was made with
flat, rigid, UV-transmissible material (Figure 1). Fresh enucleated
porcine eyes were de-epithelialized mechanically and perfused at 20
mmHg. Pre-experimental corneal curvature (K) was measured using
a portable auto-keratometer (Nidek KM-500), and Anterior Segment
Optical Coherence Tomography (AS-OCT) imaging was performed.
Following the conventional CXL protocol, all eyes were pre-treated
with 0.01% riboflavin every 2 min. for 30 min. Each experiment
consisted of 6 treatment groups in duplicate: A) no device + no CXL,
B) 30 min. device + no CXL, C) no device + 10 min. CXL, D) 10
min. device + CXL, E) no device + 30 min. CXL, F) 30 min. device
+ CXL. Post-experimental K values and AS-OCT images were
acquired. Corneal thickness and demarcation line measurements were
obtained using Visante AS-OCT analysis software. The experiment
was repeated six times (n = 12 in each group). Two-tailed Student’s
t-test was used for statistical analysis.
Results: There was a significant decrease in corneal curvature after
30 min. CXL between group F (ΔKm = -1.54 ±0.90 D) and group
E (ΔKm = +0.34 ± 0.53 D, p < 0.001) or group B (ΔKm = +0.69 ±
1.02 D, p < 0.001). The demarcation line depth was greater in group
F than group D (p < 0.05). There was also less change in corneal
thickness in groups D & F than in the control groups (p < 0.05).
Conclusions: Application of our novel corneal shaping device
during the conventional CXL protocol can significantly decrease
corneal curvature compared to controls. AS-OCT imaging showed
comparable extent of UV cross-linking (demarcation line depth)
in eyes treated ± device. This demonstrates that our novel device
used during CXL may further benefit patients with corneal ectactic
disorders by promoting corneal strengthening and refractive
correction.
Schematic design of corneal shaping device
Experimental conditions and results for treatment groups
Commercial Relationships: Angela Zhu, None; Eva-Maria
Lackner, None; Jennifer Elisseeff, None; Albert S. Jun, None
©2015, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permission
to reproduce any abstract, contact the ARVO Office at [email protected].