Surrogate Outcomes for Progression in the Initial Stages of Diabetic Retinopathy

Diabetic retinopathy remains the most frequent cause of new cases of blindness among adults aged 20-74 years. A number of large trials have validated that laser photocoagulation is a useful treatment but the disease continues to progress in approximately 50% of eyes treated by photocoagulation. Current treatment of diabetic retinopathy is only available for advanced stages of the disease and is given independently of the diabetes disease status itself and metabolic status. Other forms of therapy targeted at the earliest stages of retinal disease are needed. Proposals for defining and accepting surrogate outcomes that appropriately evaluate the earlier stages of the retinopathy are presented in this review. The most likely candidates for surrogate outcomes are: mean difference in ETDRS retinopathy scale, 2 steps per eye, microaneurysm turnover and reduction in macular thickening.