Choroidal Neovascularization and Retinal Pigment Epithelium, and Laser Photocoagulation Treatment

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1. Choroidal Neovascularization and the Retinal Pigment EpitheliumChoroidal neovascularization (ChNV) was produced experimentally in the macular area in monkey eyes by krypton laser photocoagulation (PC).In natural course following PC, ChNV occurred in 1 or 2 weeks after PC, and developed in 3 to 4 weeks, thereafter ChNV regressed spontaneously in 5 to 8 weeks.In histological study, we found, at the developing stage of ChNV, immature ChNVs were usually accompanied with migrated retinal pigment epithelial cells (RPE). At the stage of regression, RPE have proliferated to envelope ChNV as a single cell layer (sealing off).We damaged RPE by systemic administration of sodium iodite (Na 10_3) pre or post PC, or intravitreal injection of a small amount of 1 Ornithine hydrochloride. Sodium iodite damaged RPE and the outer segment of the photoreceptors, and Ornithine damaged RPE selectively. In the eyes in which these drugs were administrated before PC, ChNV have not developed at all. In the ey … More es in which these drugs were administrated after development of ChNV, ChNV have lasted and grown in half a year without any evidence of spontaneous regression. Histologically, RPE have not shown proliferation and enveloping to ChNV in these eyes.These results showed RPE cells have close relations to development and regression of ChNV, 1) migrated RPE cells may induce growing of ChN, 2) proliferations of RPE play a role to regression of ChNV, 3) damaged RPE has not shown such a role.2. Histopathology of Laser Treatment for Experimental Choroidal NeovascularizationWe studied histopathological process of lasered lesion following laser photocoagulation (PC) for experimental choroidal neovascularization (Ch NV). We produced well-developed and long-lasting ChNVs in monkey eyes by means of intense Krypton laser PC and succeedingly intravitreal injection of 1-ornithine hydrochloride. Those ChNVs were treated by orange beam (590nm) of dye laser.After dye laser PC, clinically and fluoangiographically, in some lesions, ChNVs disappeared and the lesions became dry, however, the other lesions, ChNVs grew and the lesions lasted in wet condition. Histopathological studies were made for those PC lesions. Light and EM scopy revealed, at the dry lesions, subretinal space was filled with proliferated RPE cells and NVs were not found. At the wet lesions, new vessels were found numerously, accompanied with fibroblast-like RPE cells, fibroblast, and macrophages in subretinal space.These results showed in laser treatment, closure of ChNV is essentially necessary by PC, and insufficient PC induces further development of NV and cellular proliferation in the subretinal space, and causes failure of treatment. Less