Diabetic macular edema, resulting from increased microvascular permeability, is the most prevalent cause of vision loss in diabetes. The mechanisms underlying this complication remain poorly understood. In the current study, diabetic vascular permeability (blood-retinal barrier breakdown) is demonstrated to result from a leukocyte-mediated Fas-FasL-dependent apoptosis of the retinal vasculature. Following the onset of streptozotocin-induced diabetes, FasL expression was increased in rat neutrophils (P<0.005) and was accompanied by a simultaneous increase in Fas expression in the retinal vasculature. Static adhesion assays demonstrated that neutrophils from diabetic, but not control, rats induced endothelial cell apoptosis in vitro (P<0.005). The latter was inhibited via an antibody-based FasL blockade (P<0.005). In vivo, the inhibition of FasL potently reduced retinal vascular endothelial cell injury, apoptosis, and blood-retinal barrier breakdown (P<0.0001) but did not diminish leukocyte adhesion to the diabetic retinal vasculature. Taken together, these data are the first to identify leukocyte-mediated Fas-FasL-dependent retinal endothelial cell apoptosis as a major cause of blood-retinal barrier breakdown in early diabetes. These data imply that the targeting of the Fas-FasL pathway may prove beneficial in the treatment of diabetic retinopathy.

10-20% of individuals over the age of 65 suffer from agerelated macular degeneration (AMD), the leading cause of severe visual impairment in humans living in developed countries. The pathogenesis of this complex disease is poorly understood, and no efficient therapy or prevention exists to date. A precondition for AMD appears to be the accumulation of the age pigment lipofuscin in lysosomes of retinal pigment epithelial (RPE) cells. In AMD, these cells seem to die by apoptosis with subsequent death of photoreceptor cells, and light may accelerate the disease process. Intracellular factors leading to cell death are not known. Here we show that the lipophilic cation N-retinyl-N-retinylidene ethanolamine (A2E), a lipofuscin component, induces apoptosis in RPE and other cells at concentrations found in human retina. Apoptosis is accompanied by the appearance of the proapoptotic proteins cytochrome c and apoptosis-inducing factor in the cytoplasm and the nucleus. Biochemical examinations show that A2E specifically targets cytochrome oxidase (COX). With both isolated mitochondria and purified COX, A2E inhibits oxygen consumption synergistically with light. Inhibition is reversed by the addition of cytochrome c or cardiolipin, a negatively charged phospholipid that facilitates the binding of cytochrome c to membranes. Succinate dehydrogenase activity is not altered by A2E. We suggest that A2E can act as a proapoptotic molecule via a mitochondria-related mechanism, possibly through site-specific targeting of this cation to COX. Loss of RPE cell viability through inhibition of mitochondrial function might constitute a pivotal step toward the progressive degeneration of the central retina. Age-related macular degeneration (AMD)1 affects 10 -20% of people at an age over 65 and constitutes one of the leading causes of severe visual impairment in the elderly in industrialized nations (1). Whereas the clinical and the histopathological pictures of AMD are well known (2, 3), molecular events initiating the disease remain elusive. Major obstacles in elucidating such events are the lack of suitable animal models and the complexity of the human disease. Recent studies indicate that genetic components (4 -8) and exogenous enhancing factors (9, 10) both contribute to the pathogenesis.In the course of photoreceptor renewal, rod outer segment tips are shed and phagocytosed by the underlying cells of the retinal pigment epithelium (RPE) (11-13). It is generally believed that the accumulation of the autofluorescent age pigment lipofuscin in RPE cell phagolysosomes constitutes a predicament for the development of the disease. Lipofuscin accumulation and the formation of drusen and other deposits in the region of Bruch's membrane, which separates the pigment epithelium from the underlying choroid are considered initial steps in the pathogenesis of AMD. Drusen formation may be the result of progressive death and/or exocytosis of RPE cells in the central retina (14, 15).Lipofuscin harbors two unusual retinoids, the lipophilic cations N-ret...

Background: Macular rotation surgery comprises surgical extraction of choroidal neovascular membranes in age-related macular degeneration (AMD) and translocation of the foveal neural retina over adjacent retinal pigment epithelium.Objective: To determine whether macular translocation with 360°retinotomy can stabilize and/or improve visual acuity in patients with subfoveal choroidal neovascularization (CNV) secondary to AMD.Design: This study consisted of a standardized surgical procedure on a series of 90 consecutive patients and follow-up examinations at fixed intervals for 12 months.Participants: All patients in this study had experienced recent visual loss resulting from subfoveal CNV caused by AMD. Twenty-six patients had major macular subretinal hemorrhage, 39 patients had occult subfoveal CNV, and 25 patients had classic subfoveal CNV.Methods: Macular translocation surgery was performed between 1997 and 1999. The patients were examined preoperatively and at 3, 6, and 12 months postoperatively, including visual acuity, microperimetry, angiography, and orthoptic assessment.Results: Visual acuity increased by 15 or more letters in 24 patients, remained stable in 37 patients, and deteriorated by 15 or more letters in 29 patients at 12 months postoperatively. A secondary procedure was necessary in 17 patients because of severe complications; proliferative vitreoretinopathy was observed in 17 eyes, macular pucker in 5 eyes, and macular hole in 1 patient. Conclusion:Macular translocation is a technically demanding surgical procedure. Although the procedure has a high rate of surgical and postoperative complications, the functional and anatomical results appear to be promising for selected patients with subfoveal CNV secondary to AMD.

Macrophages have long been known to play a major role in the pathogenesis of proliferative vitreoretinal disorders. Using the monoclonal antibodies EBMIl (pan macrophage), 27E10 (early inflammatory stage marker), and RM3/1 (healing phase marker), different subpopulations of macrophages were differentiated in surgically removed membranes from patients with macular pucker (n=6), proliferative vitreoretinopathy (PVR) following rhegmatogenous retinal detachment (n=1l), traumatic PVR (n=19), and proliferative diabetic retinopathy (PDR) (n=11). Macrophages were predominantly found in traumatic PVR and PDR. Some healing phase (RM3/1) macrophages were detected in all disease entities. Inflammatory stage macrophages (positive staining for 27E10) could not be detected in PVR following rhegmatogenous retinal detachment and idiopathic macular pucker. In traumatic PVR inflammatory stage macrophages were associated with a short history of disease whereas in PDR all types of macrophages could be detected regardless of clinical history and duration of the disease. (BrJ Ophthalmol 1993; 77: 731-733)

Background: Transplantation of autologous iris pigment epithelium (IPE) into the subretinal space has been suggested as one approach for the treatment of age-related macular degeneration, as well as for other conditions in which loss of retinal pigment epithelium (RPE) occurs. Surgical removal of choroidal neovascular membranes is associated with traumatic loss of the RPE cell layer, disruption of the integrity of the photoreceptor-RPE complex, and limited visual outcome. Objective: To examine whether IPE cells can substitute for RPE cells to be transplanted to the subretinal space of patients with either RPE degenerative disease or traumatic loss of the RPE cell layer after subretinal surgery. Methods: Autologous IPE cells were transplanted to the subretinal space in 20 consecutive patients undergoing removal of subretinal fibrovascular membranes using pars plana vitrectomy. Autologous IPE cells were harvested by iridectomy, isolated, and transplanted directly to the subretinal spaces. Transplants were evaluated for 6 to 11 months by funduscopy, fluorescein angiography, and scanning laser ophthalmoscopic (SLO) microperimetry. Results: For the entire follow-up period, no evidence of any immunologic response was observed. Revisional surgery was necessary in 3 patients because of complications (rhegmatogenous retinal detachment [n=1]; proliferative vitreoretinopathy [n=1]; and macular pucker [n=1]); 1 patient did not receive IPE cells. Five of 19 phakic eyes underwent cataract surgery; in 1 case this was combined with the vitrectomy. Five patients showed improved visual acuity of 3 to 4 lines, 13 patients had stable visual acuity (±2 lines), and 2 patients had reduced visual acuity of 6 lines. Conclusions: In this pilot study, the transplantation of autologous IPE cells was done as an addition to conventional surgical excision of choroidal neovascular membranes. Transplanted cells were well tolerated in the subretinal space and did not adversely affect the function of the photoreceptors, since improvement or stable visual acuity was observed in 18 patients after IPE transplantation. These results suggest that autologous IPE cells may be used as a substitute for autologous RPE cells to transplant to the subretinal space to treat age-related macular degeneration.