Material and Methods: 35 eyes of 26 patients who received panretinal photocoagulation after diagnosis of severe nonproliferative diabetic retinopathy and proliferative diabetic retinopathy were included in this prospective study. Best corrected visual acuity, intraocular pressure, slit lamp examination, fundus examination, color fundus photography, fluorescein angiography, subfoveal choroidal thickness and central macular thickness measured by optical coherence tomograhy. Measurements were recorded before and from one week and one month after the end of the panretinal photocoagulation. Friedmans\' Anova and Pearson correlation analysis were used as statistical methods. p values <0.05 were considered statistically significant.

Results: The mean age of patients was 57.35±6.32 years. The mean duration of diabetes diagnosis was 15.23±8.93 months and mean HbA1c level was 8.35±1.29. Eight patients were with nonproliferative diabetic retinopathy and eighteen patients were with proliferative diabetic retinopathy. Mean subfoveal choroidal thickness was 311.63±53.53 before and 311.63±53.53 micron after completion of panretinal (p=.000). Mean central macular thickness was 271.77±21.25 before and 284.57±19.83 micron after completion of panretinal (p=.000). There was no significant difference between best corrected visual acuity before and after panretinal (p=.068). There was no significant difference between IOP before and after panretinal (p=.097).

Conclusion: Panretinal photocoagulation increases subfoveal choroidal thickness and macular thickness in patients with diabetic retinopathy. We believe that further studies with longer follow-up time is required. Keywords : Diabetic retinopathy, optical coherence tomography, panretinal photocoagulation