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.
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