Combination Bevacizumab and Comprehensive Grid Subthreshold Laser Using a Minimum of 900 Spots as compared to Bevacizumab alone for treatment of Diabetic Macular Edema

Abstract

Purpose: : The RESTORE study has established the role of vascular endothelial growth factor (VEGF) inhibition in the treatment of diabetic macular edema (DME). Our purpose is to evaluate the combination of VEGF inhibition with comprehensive grid subthreshold laser to the macula using a minimum of 900 spots as compared to VEGF inhibition alone.

Methods: : A retrospective chart review of patients with DME was conducted comparing treatment with a combination of Bevacizumab and comprehensive grid subthreshold laser to patients treated with Bevacizumab alone. Inclusion criteria included all patients with DME treated with single-session focal laser using a minimum of 900 spots in combination with Bevacizumab and patients with DME treated with Bevacizumab alone. Twenty Five eyes of 19 patients met criteria for inclusion in this study, 14 eyes were treated with Bevacizumab and comprehensive grid laser and 11 eyes were treated with Bevacizumab alone. Comprehenive sub-threshold treatment was defined as no blanching to mild graying of the retina. The Pascal laser was used for all grid pattern laser and parameters ranged from 75 to 125 mW power, 10 to 20 millisecond duration, and 50-100 micron spot size. The main outcome measure was change in mean macular thickness by OCT.

Results: : Mean macular thickness as measured by OCT declined in both groups. With treatment of Bevacizumab alone, the average macular thickness decreased from 345 micrometers to 308 micrometers and this difference was statistically significant (p<0.03) by the Wilcoxon Signed-Rank Test. Macular thickness also decreased in the group treated with combination Bevacizumab and Subthreshold Laser with average macular thickness decreasing from 383 micrometers to 333 micrometers and this difference was also statistically significant (p<0.01) by the Wilcoxon Signed-Rank Test. There was greater decrease in average macular thickness in the group treated with Bevacizumab and subthreshold laser as compared to Bevacizumab alone (50 micrometers vs. 36 micrometers) but this difference was not statistically significant by the Mann-Whitney U Test (p=0.11).

Conclusions: : In a small cohort of 25 eyes with DME, both combination intravitreal Bevacizumab with single-session comprehensive grid subthreshold laser and Bevacizumab alone demonstrated statistically significant improvement in macular thickness. However, Bevacizumab with comprehensive grid subthreshold laser did show a trend to larger reductions in average macular thickness and we propose that this is an effective treatment of DME.

Keywords: diabetes • macula/fovea • retina