Download Wednesday, May 5, 3:45 PM - 5:30 PM Hall B/C Poster Session

Wednesday, May 5, 3:45 PM - 5:30 PM Hall B/C Poster Session Program Number/Board # Range: 5003 - 5041, 6403 / D851 - D889A
479. Ocular Blood Flow And Oxygenation II Organizing Section: PH Contributing Section: AP
5035 - D883
Effects of Plasma Kallikrein on Retinal Vascular Functions in Diabetes
A.C. Clermont1, J. Liu1, P. Riva1, T. Kita1, S. Sinha2, T. Chilcote2, E.P. Feener1. 1Beetham
Eye Institute, Joslin Diabetes Center, Boston, MA; 2ActiveSite Pharmaceuticals, Inc,
San Francisco, CA.
Purpose: Diabetic retinopathy and macular edema are associated with increases in retinal
vascular permeability (RVP) and alterations in retinal blood flow (RBF). Previously, we
have shown that plasma kallikrein (PK) is present in vitreous samples obtained from
patients with advanced diabetic retinopathy and systemic administration of a PK inhibitor
reduced RVP in rats with hypertension. In this study, we examine the effects of PK on
RVP and RBF in rats with diabetes.
Methods: Diabetes was induced in Sprague Dawley rats by IP injection with streptozotocin.
We administered the PK inhibitor (ASP-440) or vehicle alone via subcutaneous Alzet
osmotic pumps immediately after confirmation of hyperglycemia (primary intervention
study) or 2 weeks after diabetes onset (secondary intervention study). RVP and RBF were
measured after 4 weeks of diabetes duration. Effects of direct administration of PK in
the vitreous on RVP was measured following intravitreal injection of activated plasma
kallikrein PK(act) in nondiabetic (NDM) or 4 week duration diabetic (DM) rats. RBF was
measured using video fluorescein angiography. RVP was measured using Evan’s blue
dye permeation and vitreous fluorophotometry.
Results: In the primary intervention study, RVP increased 2.7 fold (p<0.01) in DM vehicle
rats compared to NDM. ASP-440 decreased DM RVP by 42% (p=0.013) and 83% (p<0.001)
at doses of 0.2 and 0.6 mg/kg/d, respectively. In the secondary intervention study, RVP
was increased by 2.3 fold (p=0.002) in DM vehicle rats compared to NDM controls.
Administration of ASP-440 at 0.6 mg/kg/d decreased DM RVP by 56% (p=0.011) compared
to DM vehicle. In DM rats, retinal mean circulation time (MCT) was prolonged (1.62±0.3
vs 0.97±0.2 s, p<0.001) and RBF was reduced (152±33 vs 255±16, p=0.001) compared to
NDM rats. Secondary intervention with ASP-440 improved DM MCT (1.26±0.3s, p=0.015)
and RBF (240±68, p=0.001) compared to DM vehicle alone. Intravitreal injection of PK
increased acute RVP by 34% (n=6) and 67% (n=9) compared to vehicle-injected eyes (both
P<0.05)in NDM and DM rats respectively. The response to PK in DM rats was 74% greater
(p=0.037) than in NDM rats.
Conclusions: These results show that systemic administration of the PK inhibitor, ASP440, ameliorates retinal vascular abnormalities associated with diabetes. The effects of
PK on the retinal vasculature in diabetes may be due to a combination of increased levels
of PK and a hypersensitivity of the diabetic retina to PK’s actions.
CR: A.C. Clermont, None; J. Liu, None; P. Riva, None; T. Kita, None; S. Sinha, ActiveSite
Pharmaceuticals, P; T. Chilcote, ActiveSite Pharmaceuticals, P; E.P. Feener, None.
Support: Juvenile Diabetes Research Foundation, NIH EY019029, Massachusetts Lions
Eye Research.
5037 - D885
Retinal Oxygenation in Patients With Systemic Hypoxia
S. Traustason1, A.S. Jensen2, H.S. Arvidsson1, I.C. Munch1, L. Søndergaard2, M. Larsen1.
1
Department of Ophthalmology, Glostrup University Hospital, University of
Copenhagen, Glostrup, Denmark; 2Department of Cardiology, Rigshospitalet,
Copenhagen, Denmark.
Purpose: To assess the effect of chronic systemic hypoxia on retinal oxygenation.
Methods: Ten patients in total were recruited, 9 of which were diagnosed with
Eisenmenger’s syndrome (bidirectional cardiac shunt caused by a ventricular
septal defect) and one patient with vena cava to pulmonary artery anastomosis.
Non-invasive spectrophotometric oximetry was used to measure the
oxygen saturation in 1st and 2nd degree arteries and veins of the superior
and inferior temporal retinal vessel arches. Additionally, the peripheral
systemic oxygen saturation was measured with a finger pulse oximeter.
These results were compared with measurements from 11 healthy volunteers.
Results: Oxygen saturation values were averaged between three consecutive images
of the superior and inferior arches. Mean peripheral systemic oxygen saturation in
the normal subjects was 98 % (97-99% total range) and 90 % (87-94% total range) in
the ischemic group. Results from the retinal oxygen saturation measurements can
be seen in table 1.
The results presented in table 1 can be recalculated to PO2, using the oxyhaemoglobin
dissociation curve. The PO2 values were 62 mmHg and 30 mmHg, respectively for
arteries and veins in the healthy volunteers, compared to 46 mmHg and 23 mmHg in
patients with chronic systemic hypoxia.
Conclusions: Oxygen saturation is lower in both retinal arteries and veins in
hypoxic patients, compared to normal individuals. Due to the non-linearity of the
oxyhaemoglobin dissociation curve, this indicates that the retinal tissue in patients
with chronic hypoxia operates at considerably lower levels of PO2 than in healthy
individuals.
CR: S. Traustason, None; A.S. Jensen, None; H.S. Arvidsson, None; I.C. Munch,
None; L. Søndergaard, None; M. Larsen, None.
Support: None
5036 - D884
MRI Reveals Decreased Retinal and Choroidal Blood Flow in a Mouse Model of
Glaucoma (DBA/2J)
W. Lavery1A, E.R. Muir1B, J.W. Kiel1A, R.C. Renteria1C, T.Q. Duong1B,1A. AOphthalmology,
B
Research Imaging Institute, CPhysiology, 1UT Health Science Center - San Antonio,
San Antonio, TX.
Purpose: Glaucoma, a leading cause of irreversible blindness worldwide, is
characterized by a progressive degeneration of retinal ganglion cells and the optic
nerve. Glaucoma is often associated with elevated intraocular pressure (IOP). A
longstanding hypothesis is that the elevated IOP exerts a compressing force on the
blood vessels, reducing blood flow (BF) to the retina and the optic nerve. DBA/2J mice
develop an optic neuropathy similar to glaucoma. The present study employs magnetic
resonance imaging (MRI) to examine the hypothesis that glaucoma is mediated by
dysregulation of ocular blood flow in this mouse model.
Methods: Depth-resolved quantitative BF MRI (42x42x400μm) was performed on
6-month old DBA/2J glaucomatous mice (considered to be mid-stage of the disease,
n= 5) and controls (C57BL6 strain, n= 6) under 1.2% isoflurane anesthesia with IACUC
approval. BF images were acquired with echo-planar imaging using a novel arterial
spin labeling MRI technique and a custom-made eye coil at 7 Tesla. The MRI parameters
were: 6x6 mm field of view, 144x144 matrix, a single 0.4 mm slice, 2 shots, 2.94 s
labeling pulse, 3.0 s repetition time, and 13 ms echo time. BF maps were calculated.
Automated profile analysis was performed to average layer-specific BF along the
length of the retina.
Results: BF MRI unambiguously quantifies choroidal and retinal BF. In normal
animals, choroidal BF was 4.2±1.0mL/g/min (mean±SD, n=6), and retinal BF was
0.94±0.19 mL/g/min. The choroidal BF was 4.4 times higher than retinal BF (P < 0.0001),
consistent with those reported using radioactive microsphere technique in rat retinas
and previously reported MRI BF from our laboratory. In the glaucomatous eyes of
the DBA/2J mice (n=5), the choroidal BF was 1.5±0.8mL/g/min and retinal BF was
0.61±0.18mL/g/min. Both choroidal (P<0.001) and retinal BF (P<0.02) were statistically
significantly different between normal and glaucomatous retinas.
Conclusions: This study, to our knowledge, is the first report of quantitative resolution
of retinal and choroidal BF using MRI. Both retinal and choroidal BF values were lower
in DBA/2J compared to control mice, consistent with the hypothesis that ischemia
may play a role in this mouse model of glaucoma. Future studies will investigate basal
BF and BF responses to stimulations as a function of disease progression. MRI has
the potential to offer depth-resolved, quantitative BF data that may prove useful for
glaucoma disease staging and therapeutic drug testing.
CR: W. Lavery, None; E.R. Muir, None; J.W. Kiel, None; R.C. Renteria, None; T.Q.
Duong, None.
Support: NEI Grant EY014211
5038 - D886
Assessment of Choroidal Blood Flow Parameters Using Flom-S Laser Doppler
Flowmeter: Reproducibility and Effect of Intense Light Exposure
A. Wang, M. Yuan, M.J. Byrnes, A. Ingerman. Ora Inc.: Retina Division, Andover, MA.
Purpose: The choroid plays an important role in supplying nutrients to and removing
waste from the outer retina, including the fovea. Abnormal choroidal blood flow
(ChBF) may therefore disrupt normal retinal function and lead to impairment of
vision. Although Laser Doppler flowmetry (LDF) has recently been applied for the
assessment of ChBF in humans, the marked variability of measurements obtained
with this technology has precluded widespread use of this technique. In this study,
we evaluated the reproducibility of LDF for ChBF parameters and assessed the effect
of prolonged exposure to intense light on ChBF.
Methods: Confocal Laser Doppler flowmetry (LDF; HES-SO//Valais) was used to
assess relative choroidal blood flow parameters - velocity (ChBvel), volume (ChBvol),
and flow (ChBflow) - in the center of the fovea. The variability of LDF was assessed by
taking multiple assessments of ChBF parameters in six subjects and calculating the
coefficients of variation (CV). The effect of exposure to intense light (40,000 cd/m2 for
2 minutes) on ChBF was assessed in five normal subjects.
Results: The following CV were observed for each parameter: ChBFvel = 5%, ChBFvol =
7% and ChBFflow = 8%. Variability of ChBF measurements was reduced with increased
experience of the LDF operator as well as increased training of the subject. In addition,
variability was also reduced by adjusting the LDF to maintain the same baseline DC
value for each measurement. After a 2 minute exposure to intense light, minimal
changes to ChBF parameters were observed (ChBFvol = 2%, ChBFve l= 1% and ChBFflow
= 3%).
Conclusion: The CV in ChBF parameters (ChBFvel, ChBFvol, ChBFflow) observed in this
study were 5%, 7% and 8%, respectively. These measurements represent a substantial
improvement over previous reports (CV of 8%, 18%, and 13%, respectively). Our results
indicate that appropriate training, standardization, and methodology, the reliability of
ChBF assessment by confocal LDF can be substantially improved. With this method, ,
we found that a 2 minute exposure to intense light did not significantly affect ChBF.
CR: A. Wang, Ora, Inc.: Retina Division, E; M. Yuan, Ora, Inc.: Retina Division, E;
M.J. Byrnes, Ora, Inc.: Retina Division, E; A. Ingerman, Ora, Inc.: Retina Division, E.
Support: None
Copyright 2010 by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved.
For permission to reproduce any abstract, contact the ARVO Office at [email protected]. Commercial Relationships are noted at the end of each abstract by “None” or with codes.
5035-5038