Download Femtosecond laser-assisted cataract incisions: Architectural stability

CORRESPONDENCE
Femtosecond laser-assisted cataract incisions:
Architectural stability and reproducibility
Samuel Masket, MD, Melvin Sarayba, MD,
Teresa Ignacio, MD, Nicole Fram, MD
There is considerable interest in the potential relationship between postoperative endophthalmitis and
clear corneal tunnel incisions for cataract surgery.1–4
Earlier work from Ernest et al.5 clearly demonstrated
that incisions that are square in surface architecture
are significantly more resistant to deformation and
leakage than those that are rectangular. The purpose
of this preliminary investigation was to determine
whether corneal tunnel incisions could be constructed
with femtosecond laser technology and in a manner
that would preclude deformation and leakage at any
intraocular pressure (IOP).
MATERIALS AND METHODS
Cadaver eyes subjected to partial-thickness clear corneal tunnel incisions constructed with an IntraLase femtosecond
laser (model 1, Abbott Medical Optics, Inc.) were studied.
A 15 kHz femtosecond laser was used to create 90% thickness corneal incisions; 3.0 mm wide, single plane–angled
incisions were generated using the side-cut feature of the
laser system. Incision tunnel lengths of 1.0 mm, 1.5 mm,
and 2.0 mm were constructed (Video; available at
www.jcrsjournal.org). A standard ophthalmodynamometer
(ODM) was used to simulate deformation of the eye, similar
to patient rubbing, following surgery. Manometric elevation
and reduction of IOP was used to test incision integrity and
various levels of pressure as the ODM device was applied
near the equator of the globe. Incisions were observed for
wound leakage determined by Seidel testing with a dry
fluorescein strip (Figure 1).
RESULTS
At variable tunnel lengths, the 3.0 mm 1.0 mm incision leaked at all levels of external pressure by the
ODM unit and at all levels of IOP. The 3.0 mm 1.5 mm incision leaked with less external pressure by
the ODM device and at lower levels of IOP; as IOP
was raised manometrically, the incision exhibited a reduced tendency for leakage. The 3.0 mm 2.0 mm
incision did not leak at any IOP despite deformation
by the ODM at full levels of indentation pressure
(Table 1).
Figure 1. A: Ophthalmodynamometer. B: The ODM calibrated standardized force (arrow) applied to equator of globe to simulate eye
rubbing or pushing on the eye following surgery.
difficult to control the length and architecture of the
incision tract. India ink penetration studies6,7 suggest
that corneal incisions are potentially physically unstable, allowing leakage from deformation of the eye
(eye rubbing, forceful blinking) early after surgery.
This pilot study addressed the feasibility of using
the femtosecond laser to construct reproducible and
stable corneal incisions. The study validates that the
femtosecond laser, although originally approved for
lamellar corneal surgery, could be adapted to generate
corneal incisions for cataract surgery as it has been
adapted for use in penetrating keratoplasty.8
Table 1. Leakage at all tunnel lengths and IOP levels.
Tunnel Length
(mm)
1.0
1.5
DISCUSSION
Femtosecond laser–assisted cataract incisions may offer added stability and reproducibility in cataract
wound construction. Currently, corneal tunnel incisions are generated with ultra-sharp blades in a single
pass (with or without a precut groove), making it
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Q 2010 ASCRS and ESCRS
Published by Elsevier Inc.
2.0
IOP
(mm Hg)
ODM
(mmHg)
5
10
20
5
10
20
5
10
20
Leaked at all levels
58
60
70
No leakage at any level
IOP Z intraocular pressure; ODM Z ophthalmodynamometer
0886-3350/$dsee front matter
doi:10.1016/j.jcrs.2010.03.027
CORRESPONDENCE
Although we believe that the current study is the
first to describe use of a femtosecond laser to produce
cataract incisions,A certain limitations of the investigation must be recognized. First, this is a pilot study with
a small sample size. Second, the behavior of cadaver
eyes may not mimic the clinical situation, as corneal
thickness increases postmortem and could produce
confounding results. Future studies should address
these limitations and include OCT incision morphology as well as wound architecture and consider a comparison of standard keratome and femtosecond laser–
generated corneal incisions.
REFERENCES
1. Masket S. Is there a relationship between clear corneal cataract
incisions and endophthalmitis? [guest editorial]. J Cataract Refract Surg 2005; 31:643–645
2. Cooper BA, Holekamp NM, Bohigian G, Thompson PA. Casecontrol study of endophthalmitis after cataract surgery comparing
scleral tunnel and clear corneal wounds. Am J Ophthalmol 2003;
136:300–305
3. Nagaki Y, Hayasaka S, Kadoi C, Matsumoto M, Yanagisawa S,
Watanabe K, Watanabe K, Hayasaka Y, Ikeda N, Sato S,
Kataoka Y, Togashi M, Abe T. Bacterial endophthalmitis after
small-incision cataract surgery; effect of incision placement and
intraocular lens type. J Cataract Refract Surg 2003; 29:20–26
4. Wallin T, Parker J, Jin Y, Kefalopoulos G, Olson RJ. Cohort study
of 27 cases of endophthalmitis at a single institution. J Cataract
Refract Surg 2005; 31:735–741
5. Ernest PH, Kiessling LA, Lavery KT. Relative strength of cataract incisions in cadaver eyes. J Cataract Refract Surg 1991; 17:668–671
6. McDonnell PJ, Taban M, Sarayba MA, Rao B, Zhang J,
Schiffman R, Chen Z. Dynamic morphology of clear corneal cataract incisions. Ophthalmology 2003; 110:2342–2348. Available at:
http://chen.bli.uci.edu/publications/J50_Ophthalmology2003.pdf.
pdf. Accessed February 20, 2010
7. Sarayba MA, Taban M, Ignacio T, Berens A, McDonnell PJ. Inflow of ocular surface fluid through clear corneal cataract incisions: a laboratory model. Am J Ophthalmol 2004; 138:206–210
8. Steinert RF, Ignacio TS, Sarayba MA. ‘‘Top hat’’–shaped penetrating keratoplasty using the femtosecond laser. Am J Ophthalmol 2007; 143:689–691
OTHER CITED MATERIAL
A. Masket S. Use of the Intralase femtosecond laser for clear corneal cataract incisions. Presented at the ASCRS Symposium
on Cataract, IOL and Refractive Surgery, Washington, DC,
USA, April 2005
Comparative effects of besifloxacin and other
fluoroquinolones on corneal reepithelialization
in the rabbit
Jin-Zhong Zhang, PhD, Kathleen L. Krenzer, OD, PhD,
Francisco J. López, MD, PhD, Keith W. Ward, PhD
Besifloxacin ophthalmic suspension 0.6% (Besivance), a newly approved fluoroquinolone for the treatment of bacterial conjunctivitis,1 has wide-spectrum
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and potent in vitro activity against common ocular
pathogens.2 Topically applied besifloxacin 0.6% has
a prolonged residence time on the ocular surface and
minimal systemic exposure.3,4 In 2 vehicle-controlled
phase III clinical studies,5,6 patients receiving besifloxacin 0.6% experienced significantly higher rates of microbial eradication and clinical resolution of bacterial
conjunctivitis than patients receiving the vehicle control. Besifloxacin is designed to have a relatively balanced dual-targeting activity, blocking both DNA
gyrase and topoisomerase IV, which suggests this
drug may have a low incidence of bacterial resistance.
This study investigated the effect of besifloxacin
0.6% on corneal reepithelialization in the rabbit. Three
other topical ophthalmic fluoroquinolonesdlevofloxacin ophthalmic solution 1.5% (Iquix), moxifloxacin
ophthalmic solution 0.5% (Vigamox), and gatifloxacin
ophthalmic solution 0.3% (Zymar)dwere tested in
parallel. Dexamethasone ophthalmic suspension
0.1% (Maxidex) was used to validate the model and
serve as a positive control. Full-thickness corneal epithelial defects (9.5 mm in diameter) were created in
the right eye of 10 New Zealand white rabbits.7 A
drop of saline, besifloxacin, levofloxacin, gatifloxacin,
moxifloxacin, or dexamethasone was applied to the
eye 0.25, 0.50, 0.75, 1, 2, 3, 6, 12, 18, 24, 36, 48, 60, and
72 hours after surgery. Slitlamp photography was performed immediately after creation of the wound and
staining by fluorescein and then after 12, 24, 36, 48,
60, and 72 hours. Images of the fluorescein-stained
incisions were measured by planimetry, and the reepithelialization rate was determined.
Dexamethasone significantly delayed corneal reepithelialization by 47% when the integrated response
was compared with that in the saline control, indicating that this rabbit model can recapitulate the
described effects of steroids on corneal reepithelialization. By 72 hours, most wounds in the saline and fluoroquinolone groups were completely reepithelialized
(R95% of the cornea was reepithelialized compared
with the 0-hour control) by clinical observation based
on the lack of fluorescein staining, and no significant
effects on corneal reepithelialization were observed
with besifloxacin (Figure 1), gatifloxacin, moxifloxacin, or levofloxacin compared with those in the saline
group at any time point. Integrated responses were
also analyzed by calculating the areas under the curve
for each treatment from 0 to 72 hours. No significant
effects were seen when the effects with besifloxacin,
gatifloxacin, moxifloxacin, and levofloxacin were compared with those in the saline group (Figure 2).
The data in the present study demonstrate that in
contrast to dexamethasone, which impedes corneal
reepithelialization,8 besifloxacin as well as the other
3 fluoroquinolones did not alter the corneal
J CATARACT REFRACT SURG - VOL 36, JUNE 2010