J. Wallace McMeel

Photocoagulation Treatment of Proliferative Diabetic Retinopathy: The Second Report of Diabetic Retinopathy Study Findings

Data from the Diabetic Retinopathy Study (DRS) show that photocoagulad inhibited the progression of retinopathy. These beneficial effects were noted to some degree in all those stages of diabetic retinopathy which were included in the Study. Some deleterious effects of treatment were also found, including losses of visual acuity and constriction of peripheral visual field. The risk of these harmful effects was considered acceptable in eyes with retinopathy in the moderate or severe retinopathy in the moderate or severe proliferative stage when the risk of severe visual loss without treatment was great. In early proliferative or severe nonproliferative retinopathy, when the risk of severe visual loss without treatment was less, the risks of harmful treatment effects assumed greater importance. In these earlier stages, DRS findings have not led to a clear choice between prompt treatment and deferral of treatment unless and until progression to a more severe stage occurs.

The Role of the Vitreous in Diabetic Macular Edema

The authors assessed retrospectively clinical records of 76 patients (125 eyes) 60 years of age or older with diabetic retinopathy who had undergone a vitreous examination. The groups consisted of 105 eyes (63 patients) with macular edema and 20 eyes (13 patients) without macular edema. Vitreous studies were done using the El Bayadi-Kajiura lens to determine whether or not the posterior vitreous was attached to the retina in the macula. Twenty-one of 105 eyes (20.0%) in the edema group and 11 of 20 eyes (55.0%) in the no-edema group had a detached posterior vitreous. This difference was found to be statistically significant, indicating that diabetic cases without macular edema have a significantly higher rate of posterior vitreous detachment than those with macular edema. This study demonstrates that the vitreous may play a role in diabetic macular edema.

Vascular Endothelial Growth Factor and Hepatocyte Growth Factor Levels Are Differentially Elevated in Patients with Advanced Retinopathy of Prematurity

Although the roles of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) in angiogenesis are well described, the putative roles of these factors in retinopathy of prematurity (ROP) remain unknown. We evaluated VEGF and HGF protein levels in subretinal fluid of eyes with ROP, and expression of their corresponding receptors in retrolental membranes associated with stage 5 ROP. We examined subretinal fluid samples from eyes using rhegmatogenous retinal detachment as a control. VEGF and HGF were differentially elevated in eyes with ROP. In Stage 5 ROP (n = 22), the mean VEGF and HGF levels were 14.77 +/- 14.01 ng/ml and 16.56 +/- 9.62 ng/ml, respectively. Interestingly, in patients with active stage 4 ROP, mean VEGF levels were highly elevated (44.16 +/- 18.72 ng/ml), whereas mean HGF levels remained very low (4.77 +/- 2.50 ng/ml). Next, we investigated in vivo expression of VEGF receptor-2 and HGF receptor in retrolental membranes from 16 patients with stage 5 ROP. Both VEGF receptor-2 and HGF receptor proteins were detected mainly in posterior portions of the membrane as well as in vessel walls and along the retinal interface where angiogenesis was active. These findings together suggest that VEGF and HGF play important roles in the pathogenesis of ROP.

Retinal Circulatory Changes after Scleral Buckling Procedures

The noninvasive laser Doppler technique was used to study retinal circulatory characteristics in five patients who underwent uncomplicated scleral buckling procedures. In each patient, the systolic/diastolic variation of the red blood cell speed in the retinal arteries (flow pulsatility ratio) was lower in the eye that had received an intrascleral implant and an encircling band than in the fellow eye. In one patient, an increase in flow pulsatility ratio accompanied an increase in retinal blood flow after removal of the scleral buckling elements. In another patient, the flow pulsatility ratio in the eye that had received a solid implant and an encircling band was less than the ratio in the fellow eye that had received an absorbable implant alone. Our results indicated that reduced retinal blood flow may be common after scleral buckling procedures, and may be a significant factor in otherwise inexplicable postoperative complications.

Retinal Detachment after Cataract Surgery: Surgical Results

The authors studied the results obtained by the Retina Associates in 376 eyes of 361 patients operated on for retinal detachment associated with aphakia or pseudophakia with a postoperative follow-up of at least 6 months. All eyes underwent scleral buckling. The series included 103 eyes with aphakia, 17 eyes with iris-fixated intraocular lens, 111 eyes with anterior chamber (AC) IOL, and 145 eyes with posterior chamber (PC) IOL. The overall success rate for retinal detachment was 93%, without significant difference among the different groups. The aphakia and PC IOL groups had significantly higher prevalence (63% and 60%, respectively) of visual acuity equal to or better than 20/40 compared with the AC IOL group (33%). The prevalence of postoperative corneal edema in the AC IOL group was significantly higher than in the aphakia and PC IOL groups. Preoperative vitreous hemorrhage, large retinal breaks, posterior retinal breaks, total retinal detachment, proliferative vitreoretinopathy, and the need for performing a closed vitrectomy were significant factors in predicting ultimate failure.

Laser Doppler Measurements of the Effect of Panretinal Photocoagulation on Retinal Blood Flow

The laser Doppler technique was used to measure the pulsatile characteristics of the retinal arterial blood flow in diabetic patients with severe retinopathy immediately before argon laser panretinal photocoagulation (PRP) and again one to two months after PRP. In each measurement the relative variation of the maximum red blood cell velocity, Vmax, in a major branch retinal artery was determined throughout the cardiac cycle. Flow pulsatility was defined as the ratio of Vmax at maximum systole to Vmax at minimum diastole. Following PRP, each eye showed a decrease in flow pulsatility as well as a decrease in retinal arterial and venous diameters. The measurements are consistent with an autoregulatory response of the retinal circulation to increased inner retinal oxygen concentration following PRP. Laser Doppler measurements may be a useful means of assessing the effectiveness of a particular PRP treatment.

Retinal Circulatory Changes Related to Retinopathy Progression in Insulin-dependent Diabetes Mellitus

To quantify the vascular deterioration of the diabetic retina, retinal circulatory changes in 45 insulin-dependent diabetic patients, and in 17 normal controls, were measured and divided into four groups according to severity of retinopathy. The noninvasive laser Doppler technique was used to measure the systolic/diastolic variation of red blood cell velocity (V) at sites along temporal retinal arteries. Flow pulsatility [V (systole)/V (diastole)] was 18% lower (P less than 0.00001) in the mild-retinopathy group than in normal controls, but 35% higher (P less than 0.001) in the severe-retinopathy group than in the mild-retinopathy group. Repeated measurements in three eyes during the progression from mild or moderate to severe retinopathy showed progressive increases in both flow pulsatility and mean retinal blood flow. Altered flow pulsatility appears to be a sensitive indicator of vascular alterations during the progression of diabetic retinopathy.

Macular Photocoagulation: Optimal Wavelength Selection

Relative merits of different laser wavelengths for macular photocoagulation are analyzed in terms of light scattering and light absorption in hemoglobin, melanin, and macular xanthophyll. Disadvantages of inner retinal damage in the macula caused by the blue-green argon photocoagulators in standard clinical use are discussed, along with advantages of argon green and krypton yellow light. Results of treatment of subretinal neovascularization in disciform macular degeneration are presented. A repetitive treatment, close follow-up protocol was employed with the objectives of closing neovasculature and preserving central visual field. In 74 successive patients treated with monochromatic argon green radiation, neovasculature was closed in 93%, central visual field loss was reduced or stabilized in 76%, and visual acuity was improved or stabilized in 70%. Results were analyzed in terms of location and size of the neovascular membrane, and it was found that best results were obtained with neovascularization farther than 600 microns from the foveola and smaller than 2 mm2. In 17 patients with neovascular membranes more than 600 microns from the foveola, neovasculature was closed in 100%, central visual field loss was reduced or stabilized in 94%, and visual acuity was improved or stabilized in 88%. Similar results were obtained with monochromatic krypton yellow radiation.

Role of the Vitreous in Diabetic Retinopathy: I. Vitreous Changes in Diabetic Retinopathy and in Physiologic Aging

The vitreoretinal relationships in 1021 eyes of 570 patients with diabetic retinopathy and in 857 normal eyes were studied retrospectively in an attempt to identify the vitreous changes specifically related to diabetes. Complete posterior vitreous detachment (PVD) occurred in diabetic patients largely as part of the aging process, but proliferation interfered with its development. Complete PVD with nonproliferative diabetic retinopathy in the younger age groups was more prevalent in eyes treated by panretinal photocoagulation (PRP) than in untreated eyes and thus might have an association with PRP treatment. Partial PVD, seen mainly in proliferative diabetic retinopathy, had no correlation with aging. In the eyes of patients who were younger when diabetes was diagnosed, the development of partial PVD had a close correlation with the duration of diabetes. The data suggest the need for a clinical trial of early photocoagulation, before partial PVD develops, in younger-onset diabetic patients showing early proliferative changes.

Retinal Blood Flow and Nerve Fiber Layer Measurements in Early-Stage Open-Angle Glaucoma

PURPOSE To evaluate the relationship between retinal circulatory abnormalities and retinal nerve fiber layer (RNFL) thinning in early-stage open-angle glaucoma (OAG) to help elucidate the mechanisms underlying the development of glaucomatous optic neuropathy. DESIGN Prospective cross-sectional. METHODS Twelve patients with early OAG and a known maximum untreated intraocular pressure less than 22 mm Hg (age, 61.4 +/- 9.7 years; Humphrey visual field mean deviation -2.7 +/- 2.1) and eight age-matched healthy control subjects (age, 58.5 +/- 8.3 years) were included in the study. Blood column diameter, centerline blood speed, and retinal blood flow were measured in the major inferior temporal retinal artery using a Canon laser Doppler blood flow instrument (CLBF 100; Canon, Tokyo, Japan). Peripapillary RNFL thickness was measured using a Stratus optical coherence tomography instrument. RESULTS On average, there were significant reductions in retinal blood speed (P = .009) and flow (P = .010) in OAG patients compared to controls. The RNFL was significantly thinner in the OAG patients compared to controls (P = .002). There were significant inverse correlations between retinal blood flow and average RNFL thickness and RNFL thickness in the inferior quadrant within the glaucoma group (Rsq = 0.50, P = .01; Rsq = 0.62, P = .003). CONCLUSION The results showed that a thinner RNFL was associated with a higher retinal blood flow in patients with early-stage OAG. The mechanisms underlying this phenomenon remain to be elucidated.