Observational study of the development of diabetic macular edema following panretinal (scatter) photocoagulation given in 1 or 4 sittings.

Objective: To compare the effects of single-sitting vs 4-sitting panretinal photocoagulation (PRP) on macular edema in subjects with severe nonproliferative or early proliferative diabetic retinopathy with relatively good visual acuity and no or mild center-involved macular edema.
Methods: Subjects were treated with 1 sitting or 4 sittings of PRP in a nonrandomized, prospective, multicentered clinical trial. Main Outcome Measure Central subfield thickness on optical coherence tomography (OCT).
Results: Central subfield thickness was slightly greater in the 1-sitting group (n = 84) than in the 4-sitting group (n = 71) at the 3-day (P = .01) and 4-week visits (P = .003). At the 34-week primary outcome visit, the slight differences had reversed, with the thickness being slightly greater in the 4-sitting group than in the 1-sitting group (P = .06). Visual acuity differences paralleled OCT differences.
Conclusions: Our results suggest that clinically meaningful differences are unlikely in OCT thickness or visual acuity following application of PRP in 1 sitting compared with 4 sittings in subjects in this cohort. More definitive results would require a large randomized trial. Application to Clinical Practice These results suggest PRP costs to some patients in terms of travel and lost productivity as well as to eye care providers could be reduced.
Trial Registration: clinicaltrials.gov Identifier: NCT00687154.