Tomographic Assessment of Laser Photocoagulation for Clinically Significant Diabetic Macular Edema

Abstract

Abstract: : Purpose:to evaluate foveal retinal thickness with optical coherence tomography (OCT) before and after laser photocoagulation for clinically significant diabetic macular edema (CSDME) and to assess the correlation between foveal thickness and best corrected visual acuity (BCVA). Methods:OCT retinal thickness maps of 25 eyes (20 patients) with mild to moderate non proliferative diabetic retinopathy and CSDME were prospectively evaluated before and after laser photocoagulation. The central foveal thickness (the average of the 6 central foveal measurements) was measured automatically using the OCT software "retina map" algorithm. Change in OCT retinal thickness was considered significant if it differed by more than the reproducibility of the instrument in patients with CSDME (50 µm). OCT exams and BCVA were obtained every 3 months up to 1 year (median follow-up of 6 months). BCVA was measured using ETDRS charts and expressed on a logarithmic scale (logMAR). The correlation of the BCVA with central foveal thickness was determined. Results:The initial mean central foveal thickness of 296 +/- 102 µm did not differ significantly from the final mean central foveal thickness of 300 +/- 111 µm (P < .01, paired t test). Following laser photocoagulation, the central foveal thickness significantly decreased in 7 of the 25 eyes (28%), remained unchanged in 13 eyes (52%) and increased in 5 eyes (20%). In 6 of the 7 eyes with significant decrease, BCVA improved by at least 1 ETDRS line. The final central foveal thickness correlated with BCVA (correlation coefficient, 0.67; P < .01 Spearmans rank test). Conclusions: This study suggests that in the majority of cases central foveal thickening remains stable or decreases after laser photocoagulation for CSDME. BCVA improvement generally correlates with a significant decrease in central foveal retinal thickening. OCT is useful in objectively assessing the response to photocoagulation for CSDME.

Keywords: diabetic retinopathy • laser • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S