AIM: To evaluate the effect of a combination therapy regimen, utilizing 3 monthly ranibizumab injections followed by 577nm laser macular grid photocoagulation(MGP)for treatment of severe diabetic macular edema(DME).

METHODS: Thirty-eight patients(53 eyes)with severe DME were divided into combination therapy group(20 patients, 28 eyes)and ranibizumab monotherapy group(18 patients, 25 eyes)randomly. All patients initially received 3 monthly ranibizumab injections(loading phase)and additional injections pro re nata(PRN). Patients in combination therapy group additionally received 577nm laser MGP during the first month after the loading phase. Change in best corrected visual acuity(BCVA)and central macular thickness(CMT)from baseline to 12mo as well as the mean number of injections after the loading phase were compared between the two groups.

RESULTS: Change in BCVA from baseline in combination therapy group and ranibizumab monotherapy group at 3, 6, 9 and 12mo were 7.6±7.9 letters vs 8.5±5.8 letters, 7.2±6.1 letters vs 7.5±6.4 letters, 8.3±6.6 letters vs 8.4±8.1 letters, 7.9±7.1 letters vs 6.5±6.3 letters respectively. Change in CMT at 3, 6, 9 and 12mo were 131± 162μm, 108± 131μm, 115± 129μm, 126± 157μm in combination therapy group as well as 129±117μm, 96±117μm, 104±135μm, 101±112μm in monotherapy group. The difference between the two groups was not statistically significant. In combination therapy group, significantly less injection was required after the loading phase(0.87±1.35 vs 2.96±2.07,t=1.714, P<0.01). By 12mo, 43% of patients in the combination therapy group had need for additional ranibizumab injections as compared to 84% in monotherapy group(t=1.385,P<0.01).

CONCLUSION: The 577nm laser MGP combined with ranibizumab injection demonstrated markedly visual gains and CMT decrease in DME patients. Retreatment rate and number of injections were significantly lower in combination therapy group compared to ranibizumab monotherapy group.