Tissue specific damage to the retinal pigment epithelium: Mechanisms and therapeutic implications

Photocoagulation is a proven treatment modality for a number of retinal diseases. In pan-retinal ablation, considerations of heat flow and the magnitude of retinal damage in terms of inner retinal loss is of limited consequence unless nerve-fiber involvement occurs with associated field loss. In contrast, focal treatment of central retinal pathologies, such as diabetic maculopathy and sub-retinal neovascularizations, demands that care be taken to minimize retinal damage and preserve central visual function. In photocoagulation, the extent to which progressively more retinal damage occurs is related to the passage of temperature transients away from the retinal pigment epithelium. If localized damage to the RPE could be achieved, then this would enable many more cases to be treated. The present paper reviews those biophysical factors which might be exploited to localize damage to achieve this end. Four schemes were examined. It is concluded that repetitive-pulse photocoagulation may prove to be the most promising technique.