Long-Term Effects of Anti-VEGF Therapy versus Panretinal Photocoagulation on Retinal Vessel Caliber in Eyes with Proliferative Diabetic Retinopathy

Abstract

Purpose: To evaluate the long-term effects of ranibizumab compared with panretinal photocoagulation (PRP) on retinal vasculature in eyes with proliferative diabetic retinopathy (PDR).

Design: Post hoc analysis of DRCR Retina Network Protocol S randomized clinical trial.

Participants: Adults with type 1 or 2 diabetes and PDR in at least 1 eye.

Methods: Integrative Vessel Analysis software was used to measure central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) of vessels at 1 disc diameter from the optic nerve edge on fundus photographs at baseline, 2 and 5 years for study eyes randomized to ranibizumab or PRP treatment for PDR. Changes in CRAE and CRVE were analyzed using mixed linear regression models with multivariable adjustments.

Main outcome measures: Mean change in CRAE and CRVE from baseline to 2 and 5 years.

Results: Data from 107 eyes (90 participants) in the ranibizumab (n = 48) and PRP group (n = 59) were analyzed. For the ranibizumab versus PRP groups, CRAE decreased by a mean of 2 versus 12 μm at 2 years (mean difference, 10 μm; 95% confidence interval [CI], 4-16; P = 0.003); and 9 versus 13 μm at 5 years (mean difference, 4 μm; 95% CI, -2 to 10; P = 0.22). Central retinal venular equivalent decreased by 14 versus 19 μm at 2 years (mean difference, 4 μm; 95% CI, -3 to 11; P = 0.26) and 18 versus 28 μm at 5 years (mean difference, 11 μm; 95% CI, 3-19; P = 0.01).

Conclusions: In patients with PDR, CRAE and CRVE decreased in both the ranibizumab and PRP groups at 5 years, but the rates of change before and after 2 years may be different. In this subset of eyes from Protocol S, the greater reduction in CRAE in the PRP group was statistically significant at 2 years but not at 5 years. For CRVE, the PRP group decreased more than the ranibizumab group, but the difference was statistically significant at 5 but not 2 years. Future research may investigate the underlying causes for retinal arteriolar and venular narrowing after treatment for PDR, and the possibility of an anatomic correlation with visual field loss.

Financial disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Panretinal photocoagulation; Proliferative diabetic retinopathy; Protocol S; Retinal vasculature.