Efficacy of subthreshold micropulse laser in the treatment of diabetic macular edema is influenced by pre-treatment central foveal thickness

Purpose To determine if the severity of diabetic macular edema influences the effectiveness of subthreshold micropulse (STMP) laser treatment. Methods A total of 63 eyes of 58 patients with diabetic macular edema were divided into two groups based on their initial central foveal thickness (CFT). Group 1 had CFT <= 400 mu m, group 2 had CFT >400 mu m. The change from baseline in CFT and visual acuity were compared at 3, 6 and 12 months follow-up. Patients were considered for retreatment with micropulse laser at 3 months if macular edema had not improved. Patients were considered for rescue anti-VEGF injections if there was clinically significant macular edema at 6 months follow-up. Number of laser retreatments, injections, and any adverse effects from STMP laser were recorded. Results Group 1 (n = 33) experienced an average of 55 mu m reduction in CFT and 0.2log MAR gain in visual acuity at 12 months (P < 0.001). No patient required rescue anti-VEGF injections. Group 2 (n = 30) experienced no significant change in CFT or visual acuity by 6 months despite retreatment with STMP in 19 eyes. From 6 to 12 months follow-up, all the patients in group 2 received rescue Bevacizumab injections that resulted in 307 mu m reduction in CFT and 0.3log MAR improvement in visual acuity (P < 0.001). No adverse effects from STMP laser were recorded. Conclusion Severity of edema can influence the effects of STMP laser. STMP monotherapy is safe and effective in treating edema of mild to moderate severity.