A quantitative in vivo study of retinal thickness before and after laser treatment for macular edema due to retinal vein occlusion

PURPOSE. TO evaluate quantitatively the effect of grid laser photocoagulation in macular edema due to central and branch retinal vein occlusion, using the retinal thickness analyzer. METHODS. Five patients with cystoid and non-cystoid macular edema were studied before and after argon grid laser treatment. All were examined clinically, with fluorescein angiography, and measurement of retinal thickness. Macular thickness was correlated to visual acuity measured on the ETDRS chart. RESULTS. Laser-slit images obtained with the retinal thickness analyzer in patients with macular edema disclosed discrete intraretinal changes after photocoagulation. Biomicroscopy and fluorescein angiography were insensitive to these small changes in the retinal thickness. No patient had any change in visual acuity after three months, but the retinal thickness was greater at this interval. The retinal thickening may be explained by a postoperative inflammatory response or by altered retinal blood flow or, in two of the eyes, by the effect of combined peripheral photocoagulation. CONCLUSIONS. The retinal thickness analyzer offers a refined tool for the diagnosis of subclinical changes of macular edema in retinal vein occlusion and is therefore also useful for assessing the effects of treatment.