Quantitation of retinal ablation in proliferative diabetic retinopathy

We studied 294 eyes of 182 patients, to quantitate the amount of retinal ablation required for regression of proliferative diabetic retinopathy.

Eyes included in the study had two or more proliferative diabetic retinopathy risk factors, received panretinal photocoagulation, and had a minimum follow-up of one year. Laser photocoagulation or cryotherapy was given to eyes that failed to regress or had progression of retinopathy. Eyes treated by other physicians, treated with xenon arc photocoagulation, or undergoing laser treatment or vitrectomy for other retinal conditions were excluded. The total area of retina ablated was calculated and used as a quantitative measure of treatment.

Regression was observed in 275 eyes (93%); 19 eyes (7%) failed to regress and eventually required vitrectomy. Panretinal photocoagulation alone successfully led to regression in 229 eyes (77%), whereas 46 eyes (15.6%) required both photocoagulation and peripheral anterior retinal cryotherapy. An average of 1.7 treatments per eye led to regression. Eyes were bimodally distributed by requirement for treatment, into low and high treatment groups. Low treatment eyes received an average of 510 mm2 of retinal ablation (2,600 500-microns burns), and high treatment eyes, 1,280 mm2 (6,500 500-microns burns). More extensive treatment was required with more retinopathy risk factors (P = .002 for four vs three risk factors and P = .0007 for four vs two risk factors); duration of diabetes mellitus longer than 15 years (P = .004), and onset of diabetes mellitus before 30 years of age (P = .0008).

Patients with proliferative diabetic retinopathy should be treated aggressively with panretinal photocoagulation, cryotherapy, or both. The amount of initial treatment required for regression may be considerably more than that recommended by the Diabetic Retinopathy Study.