Focal photocoagulation treatment of diabetic macular edema. Relationship of treatment effect to fluorescein angiographic and other retinal characteristics at baseline: ETDRS report no. 19. Early Treatment Diabetic Retinopathy Study Research Group.

OBJECTIVE: To determine whether the efficacy of photocoagulation treatment of diabetic macular edema may be influenced by degree of capillary closure, severity or source of fluorescein leakage, extent of retinal edema, presence of cystoid changes, or severity of hard exudates. PATIENTS: Patients with mild to moderate nonproliferative diabetic retinopathy and macular edema definitely or questionably involving the center of the macula.
DESIGN: One eye of each patient was assigned to early photocoagulation; the other was assigned to deferral of photocoagulation, with follow-up visits scheduled every 4 months and photocoagulation to be carried out promptly if high-risk proliferative retinopathy developed. In this report, the beneficial effect of photocoagulation was examined in subgroups defined by severity of the characteristics specified above.
RESULTS: We found no subgroup in which eyes that were assigned to immediate focal treatment had a less favorable visual acuity outcome than those that were assigned to deferral (ie, no qualitative interaction).
CONCLUSIONS: Focal photocoagulation should be considered for eyes with clinically significant macular edema, particularly when the center of the macula is involved or imminently threatened. Trends for treatment effect to be less in eyes with less extensive retinal thickening and less thickening at the center of the macula support our previous recommendation that, for such eyes, an initial period of close observation may be preferable to immediate treatment, particularly when most of the leakage to be treated arises close to the center of the macula, increasing the risk of damage to it from direct treatment or subsequent migration of treatment scars.