The diabetic retinopathy study and the early treatment diabetic retinopathy study.

The DRS showed that the benefit of panretinal photocoagulation outweighed the risks of therapy in eyes with high-risk characteristics. The ETDRS will demonstrate if photocoagulation earlier in the course of diabetic retinopathy is safe and efficacious. Criteria will be developed for determining which eyes with macular edema are responsive to photocoagulation. The data collected on the different laser treatments should establish which techniques are most effective and least harmful. Systemic aspirin therapy to retard or reverse retinopathy will be investigated in a controlled manner.