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GHOLAM A. PEYMAN, DEAN BOK; Peroxidase diffusion in the normal and laser-coagulated primate retina. Invest. Ophthalmol. Vis. Sci. 1972;11(1):35-45.
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Diffusion processes in the normal and laser-coagulated squirrel monkey retina were studied by electron microscopy and peroxidase tracer techniques. In a group of monkeys, the right eye was coagulated with an American Optical Ruby laser. Two to three weeks later, peroxidase was injected through the pars plana, close to the surface of the retina, in both eyes of each animal. The animals were then put to death at time intervals ranging from 20 minutes to four hours after injection. In a second series of animals, the chorioretinal diffusion process was studied following laser treatment. In this group, peroxidase was injected into the cubital vein. The animals were then put to death at intervals ranging from five minutes to two hours after injection. Following intraocular injection, peroxidase diffused rapidly through the intercellular spaces in the noncoagulated retina but stopped at the tight junctions (zonulae occludentes) of the pigment epithelium. After intravenous injection, peroxidase diffused through the fenestrated endothelium of the choriocapillaries and through Bruch's membrane but, again, was unable to pass through the tight junctions of the pigment epithelium. No diffusion of peroxidase from the retinal capillaries into the tissue was observed. Laser coagulation produced a retinal scar through which intercellular peroxidase diffusion was allowed to take place in both directions across the site of the original junctional barrier. Retina-to-choroid diffusion was far more extensive than chorioretinal diffusion. Laser treatment also destroyed some choriocapillaries and altered the fenestrated endothelium of those that remained. This study complements previous findings on the avascular rabbit retina in which xenon arc photocoagulation was employed. These studies suggest that, following laser coagulation, the breakdown of pigment epithelial junctional complexes and alteration in the number and permeability of choriocapillaries are responsible for the disappearance of subretinal and intraretinal fluid in various retinal diseases.
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