Quantitative analysis of diabetic macular edema after scatter laser photocoagulation with the scanning retinal thickness analyzer

Purpose: To define the effect of scatter laser photocoagulation on foveal r etinal thickness. Methods: A commercial scanning retinal thickness analyzer was used to measu re retinal thickness. The foveal retinal thickness was measured at the cent ral area of the fundus (0.4 x 0.4 mm), The method was applied to 20 consecu tive patients (mean age, 52.4 +/- 16.9 years) with diabetic retinopathy. Me asurements were performed before and 6 weeks after scatter photocoagulation . Patients were examined by fluorescein angiography and slit-lamp biomicros copy to detect macular edema. Results: Mean foveal thickness before scatter photocoagulation was 187 +/- 45 mu m, increasing to 221 +/- 46 mu m after the treatment (P = 0.0001). Th e foveal thickness increased in 12 eyes (60%). Laser treatment increased ma cular permeability in two eyes (10%). Biomicroscopic examination revealed c entral macular thickening in one eye (5%). Visual acuity was reduced in fou r eyes (20%). Conclusions: Our results suggest that subclinical macular edema occurs afte r scatter laser photocoagulation. The retinal thickness analyzer is a sensi tive tool for early detection of macular edema after laser treatment, becau se increases in retinal thickness as small as 34 mu m cannot be assessed by slit-lamp biomicroscopy.