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PurposeIn PKC-DRS2, the efficacy of the oral PKC-β inhibitor, ruboxistaurin 32 mg/day, was measured by the primary end point of sustained moderate visual loss (SMVL: a 15 letter decrease from baseline on the ETDRS (Early Treatment Diabetic Retinopathy Study) chart sustained at least for the last 6 months of study participation). We now evaluate whether SMVL is more accurate than moderate visual loss (MVL: a single occurrence of a decrease from baseline of 15 ETDRS letters) for predicting future visual loss.MethodsStudy eyes with moderately severe to very-severe non-proliferative diabetic retinopathy, best-corrected visual acuity of at least 45 letters on the ETDRS chart (∼Snellen 20/125), and no prior pan retinal photocoagulation were evaluated in 506 patients (869 eyes) who completed 36 months of treatment.ResultsSixty-five percentage (26/40) of study eyes with the onset of SMVL within 24 months of enrolment still had SMVL at study completion (36 months). In comparison, only 24% (30/126) with MVL within 24 months had SMVL at study completion. Analyses based on data from 6, 12, and 18 months of treatment were similar.ConclusionsSMVL is a more predictable measure of subsequent visual loss than is a single time point measure of MVL.Eye (2009) 23, 209–214; doi:10.1038/eye.2008.324; published online 7 November 2008 [ABSTRACT FROM AUTHOR]

Purpose: To identify the development and progression of macular retinal pigment epithelial atrophy in eyes with neovascular (CNV) age-related macular degeneration (AMD) and to correlate with visual acuity (VA)., Design: Cohort study., Participants: Age-Related Eye Disease Study 2 (AREDS2) participants with intermediate AMD enrolled in a randomized controlled clinical trial of oral supplements. Analyses were conducted in the subset of AREDS2 participants who were also enrolled in the fundus autofluorescence ancillary (FAF) ancillary study., Methods: Color photographs and FAF images were evaluated in eyes that developed CNV. Presence of geographic atrophy (GA) prior to the incidence of CNV and the development of macular atrophy following incident CNV were assessed. Areas of hypoautofluorescence representing atrophy were measured for area and macular involvement. Enlargement rate of atrophy and change in visual acuity over time were analyzed., Main Outcome Measures: incidence and enlargement rate of atrophy and VA changes in eyes with incident CNV., Results: Incident CNV developed in 334 (9.2%) of eyes evaluated in the AREDS2 FAF substudy. Of these, 40% had macular atrophy at incidence of CNV with half of these attributable to pre-existing GA. Atrophy developed in 14.7 % of eyes over 4 years of follow-up. Mean area of atrophy was largest in eyes with pre-existing GA and CNV (5.17 mm 2 , p<0.001), and atrophy involved the center of the macula in > 65% of eyes. Mean VA letter score at the annual visit in which CNV was documented was similar in the three groups with atrophy; eyes with CNV and pre-existing GA, incident atrophy at the first visit with CNV, and atrophy during follow up (60 letters). Enlargement rate of atrophy was also similar in eyes in the three groups (1.23 - 1.86 mm 2 , p = 0.47). Eyes with macular atrophy lost more visual acuity compared to eyes without atrophy, particularly after 2 years of follow-up (-10.9 vs. - 3.6 letters, p = 0.07)., Conclusion: Atrophy is commonly seen in neovascular AMD and often can be attributed to pre-existing GA. Macular atrophy and GA appear to be a continuum of the same disease process and are both associated with poor vision.

Purpose: To perform a descriptive analysis of the effects on ocular blood flow of transpupillary thermotherapy (TTT) for occult subfoveal choroidal neovascular membranes (CNVMs) in age-related macular degeneration (AMD)., Methods: Eleven subjects with occult subfoveal CNVM due to AMD were assessed in a masked fashion by color Doppler imaging (CDI) within 24 hours before, 24 hours after, and 1 month after undergoing TTT., Results: In the posterior ciliary arteries (PCAs), there were no statistically significant changes observed in the peak systolic velocity (PSV), end diastolic velocity (EDV), or resistive index (RI) at 24 hours. At 1 month, the mean EDV decreased 36% (P = 0.0105) and the mean RI increased 3.8% (P = 0.0305) in the nasal PCA. Although there was a similar trend in the temporal PCA, the differences did not reach statistical significance. In the central retinal artery (CRA), the mean PSV decreased 16% (P = 0.0137), and the mean EDV decreased 21% (P = 0.0222) at 24 hours after treatment. There were no statistically significant differences in the CRA blood flow indices at 1 month after treatment. In the ophthalmic artery, there were no statistically significant differences observed in the mean PSV, EDV, or RI at 24 hours or 1 month after treatment., Conclusions: TTT is associated with transiently decreased volumetric blood flow in the retinal circulation 24 hours after treatment. In the posterior ciliary arteries that supply the choroid, there were no changes observed at 24 hours, but at 1 month, there was a decrease in the mean EDV and an increase in the RI in the nasal and temporal PCAs, reaching statistical significance in the nasal PCA only. This study suggests that TTT could lead to alterations in choroidal blood flow, as assessed by CDI. Further study is warranted.

Proliferative diabetic retinopathy (PDR) remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop this complication. The hallmark of PDR is neovascularisation (NV), abnormal angiogenesis that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. Pharmacologic therapy aimed at preventing NV, as an adjunct to laser treatment, or as an alternative to laser treatment, would be a welcome addition to the armamentarium. PDR could be prevented by improved metabolic control or by pharmacologically blunting the biochemical consequences of hyperglycaemia (e.g., with aldose reductase inhibitors, inhibitors of non-enzymatic glycation or by protein kinase C (PKC) inhibition). The angiogenesis in PDR could be treated via growth factor (e.g., vascular endothelial growth factor (VEGF), insulin like growth factor-1) blockade, integrin (e.g., alpha-v beta-3) blockade or extracellular matrix alteration (e.g., with steroid compounds), or interference with intracellular signal transduction pathways (e.g., PKC and mitogen activated protein kinase pathway proteins). Numerous potentially useful anti-angiogenic compounds are in development, but two drugs are presently in clinical trials for the treatment of the preproliferative stage of PDR.

Objective: To determine if intravitreal triamcinolone acetonide (TAAC) inhibits experimental choroidal neovascular membranes induced by laser trauma in a rat model., Methods: Nineteen anesthetized male Brown Norway rats received a series of 8 krypton red laser lesions per eye (647 nm, 0.05 seconds, 50 microm, and 150 mW in 17 rats, and 200 mW in 2 rats). One eye received an intravitreal injection of triamcinolone acetonide (20 microL, 0.8 mg) and the other eye received an injection of isotonic sodium chloride solution. Fundus and fluorescein angiography examinations occurred just before euthanasia and tissue processing for histopathology on day(s) 0, 1, 3, 7, 14, 21, 28, and 35., Results: From the control eyes that underwent photocoagulation at 150 mW, 57 discrete lesions with definitive fibrovascular proliferations were observed at 21, 28, and 35 days, arising from a total of 72 spots placed (79% yield). From the control eyes that underwent photocoagulation at 200 mW, 11 discrete lesions with definitive fibrovascular proliferations were observed at 28 days, arising from a total of 16 spots placed (69% yield). In the TAAC-treated group, no fibrovascular proliferations were observed in the 72 lesions and in the 16 lesions created with 150 mW and 200 mW, respectively., Conclusion: Intravitreal TAAC is a potent inhibitor of fibrovascular proliferations in a rat model of choroidal neovascular membranes induced by laser trauma., Clinical Relevance: This study corroborates previous investigations that propose TAAC as a potential treatment for choroidal neovascular membranes in humans.

Antisense oligonucleotides are a class of compounds being developed as therapeutic agents for many types of diseases. Although still relatively early in the clinical characterisation, the power of this technology lies in the ability to utilise genetic information and the known molecular mechanisms of disease to foster efficient and rational drug design. Consideration of novel approaches to treating ocular diseases is of interest because there are many ocular diseases with no satisfactory treatments. The recent availability of animal models of many ocular diseases provides the opportunity to use antisense oligonucleotides to understand the mechanisms of disease pathology and to potentially intervene therapeutically in ocular disease. There are already a number of examples where antisense oligonucleotides have been applied to the study of ocular physiology and disease and there is an antisense oligonucleotide approved for the treatment of cytomegalovirus (CMV) retinitis. We summarise current research in this area and highlight the properties of these compounds that are favourable for use as ocular therapeutics.

Cytomegalovirus (CMV) retinitis is a common ocular complication of immunosuppression. The management of CMV retinitis has been continuously evolving over the last decade. The mainstay of therapy remains ganciclovir and foscarnet. However, increasing resistance and ongoing toxicities to these agents remain a challenge. Additional frequently utilised agents include cidofovir and fomivirsen. The advent of highly active antiretroviral therapy (HAART) has allowed the restoration of immunocompetency to many patients previously challenged by CMV infection. In some circumstances, HAART has even eliminated the need for ongoing antiviral therapy. This paper reviews the current treatment modalities, including their toxicities and dosing recommendations.

We compared quantitative capillary retinopathic changes between non-insulin-dependent diabetic Zucker Diabetic Fatty (ZDF) rats and heterozygous nondiabetic Zucker controls and evaluated the effect of an orally administered glucosidase inhibitor, acarbose, on retinopathy in these animals. Four groups of eight rats were analyzed: treated and untreated ZDF and treated and untreated Zuckers. Retinal capillary basement membrane thickening and retinal capillary cell density were determined from transmission electron microscopy and trypsin digestion preparations. ZDF rats had thicker basement membranes (p<0.0001) and more cells per unit capillary length (p=0.0003) compared to Zuckers. Acarbose treatment significantly reduced basement membrane thickening in the treated ZDF rats (p=0.001), but the effects on cell density showed only a favorable trend. Acarbose treatment has an ameliorative effect on the development of microvascular retinopathy in the ZDF rat, probably due to lessening of hyperglycemia.

Purpose: To examine the effects of intravitreal injection of 4.0 mg triamcinolone acetonide on the visual and clinical course of exudative age-related macular degeneration., Methods: A randomized clinical trial of a single injection of triamcinolone acetonide into the vitreous cavity of experimental eyes at baseline versus observation of untreated subjects was performed in 27 patients followed up for 6 months. Inclusion criteria included exudative age-related macular degeneration with subfoveal or occult choroidal neovascularization, and visual acuity between 20/40 and 20/400. Examination, acuity assessment, fundus photography, and fluorescein angiography were performed at baseline and at 3 and 6 months after enrollment. LogMAR visual acuity was compared between groups by a repeated measures analysis of variance model. Masked assessment of photographic studies was performed and groups were compared with Fisher's exact test., Results: Visual acuity was significantly better in the treated group compared with control subjects at 3 and 6 months (P < 0.005). Fundus photography and angiography were more likely to show stability or improvement at 3 and 6 months in the treated group (P = 0.05). Intraocular pressure elevation was seen in 25% of treated patients, but was controlled with topical medications. Progression of cataract was more frequently seen in the treated group., Conclusions: Intravitreal triamcinolone acetonide may provide short-term improvement in visual acuity and fundus findings in exudative macular degeneration. These findings must be considered preliminary and should be followed by multicenter, masked, placebo-controlled trials with long-term follow-up.

Purpose: To confirm the occurrence of phototoxicity due to systemic fluorescein in a dose consistent with retinal angiographic testing and to approximate the prevalence of this reaction in a small group of volunteers., Methods: Fourteen volunteers underwent a controlled challenge test by applying a topical sunscreen and exposing skin areas to direct sunlight before and after fluorescein administration., Results: Two subjects experienced marked cutaneous blanching erythema, mild vesiculation, and pain in sun-exposed areas within 1 hour of exposure. The reaction faded over a period of days without tanning., Conclusions: Consistent with its in vitro properties as a photodynamic dye, fluorescein may rarely act as a phototoxic agent in humans at doses employed for fluorescein retinal angiography. It is unclear why this reaction has not been reported more frequently, given the large number of patients undergoing this ophthalmic procedure annually.

The purpose of this study was to evaluate the role of corticosteroids in managing subfoveal choroidal neovascularization (CNV) secondary to the presumed ocular histoplasmosis syndrome. The cases of eighteen patients with histoplasmosis-related subfoveal CNV treated with corticosteroids were reviewed. Ten patients received oral prednisone for 4 to 6 weeks, and eight received a single sub-Tenon's injection of triamcinalone. Visual acuity outcomes were analyzed along with side effect profiles. At two-week follow-up, the prednisone group showed a median improvement in Snellen visual acuity of +2.0 lines, while the triamcinalone group remained essentially stable with a 0.5 line median loss. At treatment end (4 to 6 weeks), both groups showed no significant change in median acuity at 0.0 and -1.0 lines, respectively. Median final vision at 3 months also remained essentially stable at -0.5 lines for each group. Three patients reported anxiety, all of whom were taking prednisone 80 mg daily. Two patients reported increased appetite and weight gain on regimens of prednisone 80 and 100 mg daily. There were no adverse effects reported in the other patients receiving oral prednisone or in any patient receiving sub-Tenon's triamcinalone. The results suggest a beneficial effect of corticosteroids in stabilizing subfoveal CNV secondary to ocular histoplasmosis. In this small series, oral prednisone resulted in a short-term improvement in visual acuity, which stabilized over longer follow-up. The sub-Tenon's triamcinalone group achieved similar final stabilization without the initial improvement. Corticosteroids may be particularly valuable in managing neovascularization in patients who are awaiting interventions currently under development, in preventing recurrence after subfoveal surgery, or in treating non-surgical candidates. Further study is warranted to define the precise role of corticosteroids in this condition.

Purpose: To study ocular perfusion defects in age-related macular degeneration., Methods: Twenty-five subjects with nonexudative age-related macular degeneration were compared with 25 age-matched control subjects in studies of flow velocities in several retrobulbar vessels. Color Doppler imaging, which was performed by an examiner who was masked to the subjects' assignment to the control or age-related macular degeneration group, measured peak systolic and end diastolic velocity in the ophthalmic, central retinal, and nasal and temporal posterior ciliary arteries of one eye. A resistive index was calculated from the peak systolic and end diastolic velocity., Results: Subjects with nonexudative age-related macular degeneration showed a consistent trend toward lower peak systolic and end-diastolic velocities in the posterior ciliary arteries. For example, in the nasal posterior ciliary artery, the mean end diastolic velocity measured 1.45 +/- 0.34 cm per sec in the age-related macular degeneration group compared with 1.96 +/- 0.66 cm per sec in the control group, yielding a 26% decrease in the age-related macular degeneration group, which represented the largest difference and was highly statistically significant (P = .0012). The resistive index was not significantly altered in the nasal or temporal posterior ciliary artery. Subjects with nonexudative age-related macular degeneration did not differ from control subjects in peak systolic velocity, end diastolic velocity, or resistive index in the ophthalmic artery. In the central retinal artery, the end diastolic velocity was lower (1.37 +/- 1.95 cm per sec vs 1.95 +/- 0.66 cm per sec), whereas the resistive index was higher (0.83 +/- 0.05 vs 0.76 +/- 0.06 cm per sec), in the age-related macular degeneration group; these results were highly statistically significant (P = .0007 and P < .0001, respectively)., Conclusions: Retrobulbar vascular changes in nonexudative age-related macular degeneration subjects include reduced flow velocities in the nasal and temporal posterior ciliary arteries. The reduced peak systolic velocity, combined with the reduced end diastolic velocity at a constant resistive index, seen in nonexudative age-related macular degeneration, is consistent with reduced bulk flow in these vessels, suggesting that choroidal perfusion is abnormal in this form of age-related macular degeneration. The changes in the central retinal artery suggest there may be a more generalized perfusion abnormality beyond the choroid in patients with age-related macular degeneration or that the central retinal artery exhibits a secondary autoregulatory response to a primary change elsewhere.

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the USA. Laser photocoagulation of choroidal neovascular membranes (CNVMs) in exudative AMD is currently the only well-studied and widely accepted treatment modality. It is beneficial for only a small minority of patients who show well-demarcated "classic" CNVMs, and it destroys normal retinal tissue, creates a scotoma, and is associated with an unacceptably high CNVM persistence and recurrence rate. Consequently, investigators have attempted to develop new modalities for treatment of CNVMs. These treatment modalities can be grouped into four major categories: photodynamic therapy; pharmacologic inhibition of CNVM formation with antiangiogenic agents; surgical intervention, including excision of subfoveal CNVMs; and radiation therapy. All of these experimental treatment modalities are directed toward destroyiing CNVMs, the end result of the exudative process, and all have limitations. The ideal treatment of the future must be based on the pathogenesis of the disease at a stage well before CNVMs develop. Investigations in nonexudative AMD are currently focusing on several major areas. Epidemiologic factors, such as genetics, sunlight, and nutrition, are being evaluated in several large studies, including the Age-Related Eye Disease Study, with the possibility of ultimately limiting the risk of AMD through behavior modification. Laser treatment of drusen is being evaluated as a means of limiting the risk of CNVM formation, although mixed results have been reported in the small number of studies to date. Choroidal perfusion abnormalities have been described in AMD, and some investigators postulate that altering blood flow may limit the risk of CNVM formation. No perfusion-treatment trials have been completed to date.

Objective: The authors tested the antiangiogenic properties of an orally administered protein kinase-Cbeta inhibitor, LY333531, in a pig model of preretinal neovascularization caused by retinal branch vein occlusion to determine the effectiveness of this therapy in preventing intraocular neovascularization from an ischemic stimulus., Methods: In 20 eyes of 10 pigs, branch retinal vein occlusions were created in a standardized manner using photodynamic thrombosis with rose bengal dye and thermal burns from an argon laser with green light. Five animals received 1 mg/kg LY333531 daily in two oral doses, and five animals were untreated. The eyes were followed clinically for 12 weeks with ophthalmoscopy, fundus photography, and fluorescein angiography. A standardized grading system permitted masked assessment of disc proliferations using stereo fundus photographs. After the pigs were killed, all neovascularization was confirmed histopathologically in a masked fashion and a final grade was assigned to each eye. The Mann-Whitney test was used for statistical analysis of the median values of the unpaired data between the two eyes of each animal (data were rounded up)., Results: Significant inhibition of neovascularization was observed in eyes from animals treated with the study drug (P = 0.03). Although some of the treated eyes demonstrated no clinically evident new vessels, histopathologic and photographic analysis demonstrated fine new vessels on the optic disc in all eyes (mean grade 1.9). All the untreated eyes developed clinically evident neovascularization (mean grade 3.1). The oral drug was well tolerated, and no side effects were documented., Conclusions: A specific protein kinase-Cbeta inhibitor, LY333531, effectively inhibited preretinal and optic nerve head neovascularization in the pig model of branch retinal vein occlusion. This was consistent with the known pathways of signal transduction by growth factors in activated cells and suggested that inhibition of this key regulatory isozyme is effective in the treatment of ischemia-mediated neovascular diseases.

Objective: Human recombinant insulin-like growth factor-1 (hrIGF-1), a ubiquitous angiogenic growth factor, was injected into the vitreous cavity of pigs to investigate the clinical and histopathologic consequences of supraphysiologic levels of this angiogenic growth factor on the retinal vasculature., Design: Young male pigs were injected with 600 microg hrIGF-1 into the vitreous cavity and were observed with serial examinations by ophthalmoscopy, fundus photography, and fluorescein angiography for varying periods up to 6 months. In a separate set of experiments, a dose-response relation was explored in animals injected with varying doses of IGF-1., Main Outcome Measures: Histopathologic analysis included light and transmission electron microscopy and modified elastase digestion. Quantitative morphometric measurements were made of capillary basement membrane thickness and endothelial cell and pericyte densities of the retinal capillaries., Results: Early clinical features of IGF-1-injected eyes included marked arteriolar tortuosity, vitreitis, and retinal vessel and optic nerve head vascular fluorescein leakage. By 4 weeks, hyperfluorescent dots consistent with microaneurysms appeared and increased in number until 8 weeks postinjection. Clinical findings did not change appreciably after 8 weeks. Elastase digestion showed microaneurysms of the retinal capillaries and no ischemia or pericyte ghosts. Quantitative analysis of the digested specimens showed increased endothelial density by 1 month after injection (P < 0.05). Transmission electron microscopic cross-sections of capillaries showed significant basement membrane thickening by 3 months (P < 0.05). Lower doses of IGF-1 showed fewer clinical and histopathologic changes, and no significant changes were noted with a single 6 microg injection. Suspending hrIGF-1 in acidic buffer produced less intraocular inflammation than use of bovine serum albumin at neutral pH., Conclusions: A single intravitreous injection of a large dose of hrIGF-1 produces a retinal microangiopathy that has a prolonged time of onset and remains stable from 2 to 6 months after injection. Some aspects of this angiopathy resemble diabetic retinopathy, suggesting growth factor effects in the morphologic vascular changes of diabetes.

Purpose: To describe a patient with iatrogenically induced central retinal vein occlusions secondary to serum hyperviscosity from intravenous immunoglobulin administration., Method: Case report., Results: The patient developed bilateral central retinal vein occlusions in association with high-dose intravenous immunoglobulins. The central retinal vein occlusions resolved when the immunoglobulins were withheld and serum hyperviscosity decreased., Conclusion: Administration of high-dose intravenous immunoglobulins can be associated with hyperviscosity syndrome manifested by central retinal vein occlusion.

Purpose: To report three cases of phototoxic reactions to intravenous fluorescein for retinal angiography and to describe provocative testing in a volunteer., Methods: Three patients with phototoxic reactions were interviewed, and one volunteer underwent a controlled challenge test by applying a potent sunscreen and exposing skin areas to direct sunlight before and after fluorescein administration., Results: All patients experienced marked cutaneous erythema, edema, and pain to sun-exposed areas within 1 hour of exposure. The reaction faded during a variable period of time, and one case resulted in mild epidermal desquamation and prolonged discomfort. We noted minimal skin changes in the volunteer who was exposed to the sun before fluorescein administration; however, marked blanching erythema and pain were noted after fluorescein administration and sunlight., Conclusions: Consistent with its in vitro properties as a photodynamic dye, fluorescein may rarely act as a phototoxic agent in humans at doses employed for fluorescein angiography.

Purpose: The authors tested the antiangiogenic properties of intravitreally administered triamcionolone acetonide in a pig model of preretinal neovascularization to determine the effectiveness of this therapy in preventing neovascularization., Methods: In 14 eyes of seven pigs, branch retinal vein occlusions were created in a standardized manner using photodynamic thrombosis with rose bengal dye and thermal burns from the argon green laser. Intravitreal injection of approximately 4 mg of triamcinolone acetonide was performed in one eye of each animal, and eyes were followed clinically for 12 weeks with ophthalmoscopy and fundus photography. A standardized grading system was developed to permit masked assessment of disc proliferations from fundus stereophotographs. After death, all neovascularization was confirmed histopathologically and a final grade was assigned to each eye. Statistical analysis employed use of a nonparametric test of the paired data., Results: Significant inhibition of neovascularization was observed in triamcinolone-treated eyes (P = 0.0156). Although none of the steroid-injected eyes demonstrated clinically evident new vessels, histopathologic and photographic analysis results demonstrated fine new vessels on the optic disc in four eyes. In all of the untreated eyes, neovascularization of a moderate (II) to high (III to IV) grade developed., Conclusions: Intravitreal triamcinolone acetonide effectively inhibited preretinal and optic nerve head neovascularization in the pig model. The grading system used permitted masked assessment of outcome and paired analysis allowed a conclusion to be drawn from a relatively small number of eyes. The mechanisms by which triamcinolone acetonide inhibits neovascularization remain to be elucidated.

Retinal collaterals are a common clinical occurrence after branch vascular occlusions in humans and laboratory animals, yet the etiology and functional significance of these vessels is uncertain. A hypothesis is presented which attempts to explain the difficult problem of retinal arterial collateral circulation. This theory is consistent with microcirculatory hemodynamic research which demonstrates that microcirculatory flow determinants are primarily guided by resistance factors and vascular geometry. Testing with a simple mathematical model and SPICE simulation of a circuit model suggests this theory can be applied to cases of both arterial and venous collaterals. While the underlying determinants of flow can be described, the exact mechanisms of vascular remodelling into large caliber vessels must be primarily cellular.

In the first year of operation, the Eye Injury Registry of Indiana collected data on 171 severe eye injuries and categorized them according to the circumstances of the injury, severity of tissue disruption and visual function. Many preventable causes of injury were documented. By understanding the contributors of accidental injury, prevention strategies can be implemented. This collaborative project should continue to provide useful information specific to Indiana concerning the root causes of eye injury.

Purpose: To determine if quantifiable morphometric signs of retinopathy occur in the Zucker diabetic fatty rat (ZDF/Gmi-fa, formerly designated ZDF/Drt), a partially inbred strain in which the genetic propensity for diabetes is only expressed in obese males., Methods: Retired diabetic (ZDF/Gmi-fa) and control lean Zucker (fa/+) breeder rats were examined for quantifiable evidence of microvascular changes of the retinal capillaries by gross examination, trypsin digestion of retinal vessels, and transmission electron microscopy., Results: Gross examination of retinas and trypsin digestion of capillaries revealed no differences. Quantitative assessment of capillary cell nuclear density showed that diabetic retinas were hypercellular compared to lean rats (3.888 +/- 0.041 versus 3.304 +/- 0.046 nuclei per 100 microns (mean +/- SE), P = 0.0042). Transmission electron microscopic analysis of retinal capillary basement membrane thickness demonstrated thicker measurements in diabetic animals (mean thickness 21% greater in diabetic rats, P = 0.0307)., Conclusions: This model may be useful for pharmacologic intervention studies because it is naturally and severely non-insulin-dependent diabetic, there are quantifiable retinal vascular changes, and same-sex litter mates can be used as controls.

Objective: To develop a reliable model of ischemic preretinal and optic nerve head neovascularization in young male domestic pigs., Methods: Using laser-induced branch retinal venous obstruction assisted by photodynamic thrombosis with rose bengal, 15 of 15 treated eyes developed neovascularization of the optic nerve head and retina. All cases of neovascularization were followed up clinically for up to 12 weeks., Results: Clinical, fluorescein angiographic, and histopathologic features were consistent with neovascular proliferation into the vitreous., Conclusions: Further evaluation of the long-term natural history, role of the degree of ischemia, and the effect of interventions for various types of ischemic retinopathy (eg, panretinal photocoagulation) is warranted. This model is simple and relatively inexpensive and allows easy clinical assessment.