Subretinal fibrosis in diabetic macular edema - ETDRS report 23

Objective: To describe the characteristics of and risk factors for subretinal fibrosis (SRF) in patients with diabetic macular edema. Patients and Methods: A total of 109 eyes (in 96 persons) with SRF, defined as a mound or sheet of gray to white tissue beneath the retina at or near the center of the macula, were identified during the Early Treatment Diabetic Retinopathy Study, which is a randomized clinical trial of photocoagulation and aspirin treatment in patients with mild to severe nonproliferative or early proliferative diabetic retinopathy. The patients and the ocular characteristics of these 109 eyes, all of which had clinically significant macular edema, were compared with those of 5653 eyes in which clinically significant macular edema, but not SRF, was observed during the trial. Results: In 9 of 109 eyes, the development of SRF may have been directly related to focal photocoagulation. Seventy-four percent of the eyes in which SRF developed had very severe hard exudates in the macula prior to the development of SRF, while this level of hard exudates was seen in only 2.5% of the eyes with clinically significant macular edema in which SRF did not develop (P<.001). Of the 264 eyes with this level of hard exudates at baseline (n=29) or during follow-up (n=235), SRF developed in 30.7% of the eyes, while this complication developed in only 0.05% of 5498 eyes with clinically significant macular edema without this level of hard exudates. Conclusions: Subretinal fibrosis is an infrequent complication of diabetic macular edema. Although it has been reported to be associated with photocoagulation burn intensity, in only 9 of 109 eyes in which SRF developed was it located adjacent to a photocoagulation-related scar (among 4823 eyes that received focal photocoagulation for treatment of macular edema). The strongest risk factor for the development of SRF is very severe hard exudate.