Factors Associated with Improvement and Worsening of Visual Acuity 2 Years after Focal/Grid Photocoagulation for Diabetic Macular Edema

Abstract

Purpose: To identify factors associated with the visual acuity outcome following focal/grid photocoagulation for diabetic macular edema (DME) among eyes randomized to the focal/grid photocoagulation treatment group within the Diabetic Retinopathy Clinical Research Network (DRCR.net) trial comparing triamcinolone with focal/grid laser. Design: Multicenter, randomized clinical trial. Participants: Three hundred thirty eyes with DME assigned to the focal/grid photocoagulation group, visual acuity 20/40 to 20/320 and optical coherence tomography (OCT) central subfield thickness ≥250 microns. Methods: Eyes were treated with a protocol-defined photocoagulation technique, which was repeated at 4-month intervals for persistent or recurrent edema. Separate logistic regression models were used to evaluate the associations of demographic, clinical, OCT, and fundus photographic variables with visual acuity improvement or worsening of 10 or more letters from baseline to 2 years. The association of the initial visual acuity outcome after treatment with the subsequent visual acuity course also was evaluated. Main Outcome Measures: Visual acuity measured with the electronic Early Treatment Diabetic Retinopathy Study method. Results: Worse baseline visual acuity was the only factor found to be associated with more frequent visual acuity improvement (P<0.001), and both greater baseline OCT-measured retinal volume (P=0.001) and better baseline visual acuity (P=0.009) were found to be associated with more frequent visual acuity worsening. Visual acuity outcomes were similar in eyes with and without prior macular or panretinal photocoagulation. The initial visual acuity outcome at 4 months was not generally predictive of the subsequent course. Many eyes that worsened 10 or more letters from baseline to 4 months subsequently improved, and many eyes that initially improved, subsequently worsened. Conclusions: At this time, focal/grid photocoagulation remains the standard management for DME and these results do not alter this paradigm.