A 5-year follow-up of photocoagulation in diabetic macular edema: the prognostic value of vascular leakage for visual loss

Abstract

To study the long-term visual result of photocoagulation of clinically significant macular edema (CSME) in diabetic patients in relation to baseline retinal vascular leakage assessed by vitreous fluorometry. The study enrolled 36 eyes in 27 diabetic patients with CSME at baseline, all subsequently treated by photocoagulation. The diagnosis of CSME and treatment procedure followed the ETDRS criteria. The leakage through the retinal vessels was calculated as the blood-retinal barrier permeability. Five years after initial photocoagulation the patients were reexamined. The mean visual acuity decreased with 16 letters at follow-up, and in 15 eyes visual loss was substantial, with a decrease of 15 letters or more, corresponding to at least 3 lines. The baseline permeability was significantly higher in eyes with substantial visual loss than in eyes with more stable vision (14.2 nm/sec and 6.3 nm/sec respectively; p = 0.006), the corresponding odds ratio was 16.1 (95% CI: 1.8-146; p = 0.014). The level of retinopathy was significantly correlated to visual loss (Fisher's exact test < 0.02). Visual acuity decreased at follow-up, and a substantial visual loss of 3 or more lines in CSME was associated with higher retinal vascular leakage at baseline with an odds ratio of 16.1. For this relatively small sample, neither diabetes duration, age or HbA(1c) reached statistical significance, indicating that blood-retinal barrier permability is a strong predictor of the visual outcome. The results support the investigation of triamcinolone or VEGF inhibition in patients with severe leakage, and may help to identify patients in need for intravitreal injection.