Healing of photocoagulation lesions affects the rate of subretinal fluid resorption

We have measured the rate of subretinal fluid resorption in rabbits by monitoring the collapse of small experimental retinal detachments (blebs) filled with either Hanks' solution (non-proteinaceous) or autologous serum. Blebs filled with Hanks' solution resorbed much more rapidly over freshly lasered RPE than normal RPE, but the effect disappeared over 10 to 14 days. This time course corresponds with angiographic and histologic evidence of RPE repair. In contrast, blebs filled with serum resorbed at nearly the same rate regardless of whether the RPE had been lasered or not. We conclude that photocoagulation destroys the RPE barrier acutely, and until the barrier heals non-proteinaceous subretinal fluid will be drawn out rapidly by the oncotic pressure of the choroid. This acute effect of photocoagulation is of uncertain benefit in clinical conditions because of protein in the subretinal fluid, and it seems more likely that photocoagulation works in serous retinopathy by arresting an active source of fluid.