The final results of a randomized controlled clinical trial of photocoagulation for diabetic maculopathy are reported, when all patients have been followed for at least 5 yr and some for as long as 7 yr. Ninety-nine patients with two similarly affected eyes had one eye chosen by a random procedure, treated with the xenon-arc photocoagulator; the untreated eyes remained as control.
The mean visual acuity deteriorated by less than one line in treated eyes but by more than 2 lines in the controls (P < 0.01). The difference in deterioration was greatest in patients whose initial vision was 6/6-6/9, and was not significant in those whose visual acuity was 6/36 or worse. Thirteen patients became blind in both eyes (visual acuity of 6/60 or less for 2 consecutive yearly assessments), 6 in the treated eye only, and 26 in the control eye only (P < 0.01). Again the divergence between treated and control eyes was most marked in those whose initial vision was 6/6–6/9, (only one treated but 10 control eyes became blind). Hard exudates, microaneurysms, and hemorrhages improved more in the treated eyes (0.05 < P < 0.001) and more control eyes developed new vessels during the follow-up period.
Twenty-three patients died during follow-up and another 16 failed to complete the study. Though the blood pressure of those who died was higher than those who survived (P < 0.05 for both systolic and diastolic) no other medical abnormalities at entry had any clear effect on visual outcome or 5-yr survival.
It is concluded that photocoagulation is of benefit in maintaining vision in diabetic maculopathy if the disease is not too far advanced.