Small, non-rhegmatogenous retinal detachments (blebs) were made in cat eyes by injecting fluid into the subretinal space, and the time course of fluid resorption was monitored. Blebs made with Hanks' solution over the pigmented RPE resorbed 22% faster than those over the tapetum. Blebs made with a non-ionic solution (isotonic sucrose) took 43% longer to resorb than those made with Hanks' solution, and blebs containing 3 X 10~3 M sodium cyanide took 32% longer than controls. These results suggest that active ionic transport is involved in the absorption of subretinal fluid in the cat, as it is in the rabbit. Oncotic pressure in the choroid may also contribute to resorption, because blebs made with autologous serum took roughly 3 times longer to resorb than those made with non-proteinaceous Hanks' solution. The retinal vascular system does not appear to contribute, since the resorption time was similar for Hanks' blebs made under normal retina and those made under ischemic retina (produced by occluding retinal branch arteries with argon laser photocoagulation or endodiathermy). Invest Ophthalmol Vis Sci 27: [1560][1561][1562][1563] 1986 In our previous studies on subretinal fluid resorption in the rabbit, we found that both metabolic activity of the retinal pigment epithelium (RPE) and choroidal oncotic pressure contribute to the resorption of fluid from under experimental non-rhegmatogenous retinal detachments. We suspect that similar mechanisms exist in the human eye, judging by the fact that subretinal fluid can be absorbed very quickly from under a rhegmatogenous retinal detachment after sealing the retinal break. However, the human eye differs from the rabbit eye in that it has an intrinsic retinal vasculature which leaks fluid in various pathological conditions and, in theory, could also help to resorb fluid. In this paper, we report on the mechanisms of subretinal fluid resorption in an animal which has an intrinsic retinal vasculature, the cat. Our primary concerns were whether metabolic transport was involved and whether the intrinsic retinal vessels contributed to the removal of fluid. Materials and Methods These investigations adhered to the ARVO Resolution on the Use of Animals in Research. Cats weigh- ing 2.1-5.8 kg were anesthetized with 35 mg/kg pentobarbital administered intraperitonealy. The pupils were dilated with two drops of 1% cyclopentolate and 10% phenylephrine. The outer canthus was incised, and some of the lateral orbital bone removed to expose the temporal scleral surface, in which a 3 mm slit was made meridionally 5 mm posterior to the limbus. The basic technique for making detachments was identical to that used for rabbits
