Retinal venular calibre dilatation after intravitreal ranibizumab treatment for neovascular age-related macular degeneration

Background: To describe the changes in retinal vascular calibre in response to intravitreal ranibizumab injections in patients with neovascular age-related macular degeneration. Design: Prospective interventional case series. Participants: Treatment naïve patients with neovascular age-related macular degeneration were recruited over a 1-year period. Methods: Each patient received three monthly intravitreal injections according to a 'loading dose'. Retinal arteriolar and venular calibre was measured from digital fundus photographs and summarized as central retinal artery equivalent and central retinal vein equivalent at baseline and 3months. Main Outcome Measure: Central retinal artery equivalent and central retinal vein equivalent changes from baseline to 3months. Results: Seventy-four eyes of 71 patients had good quality images for grading vessel calibre at baseline and at 3months in treated (study) eyes and 51 eyes of 51 patients had good quality images in fellow (control) eyes. Over 3months, in study eyes treated with ranibizumab, there was a significant increase in central retinal vein equivalent over baseline (+6.20μm, P=0.005), but no significant change in central retinal artery equivalent (+0.86μm, P=0.55). In control eyes, there was no change in central retinal vein equivalent (-0.82μm, P=0.70) or central retinal artery equivalent (0.34μm, P=0.75). Conclusion: Intravitreal ranibizumab has a significant vasodilational effect on retinal venular calibre in eyes treated for neovascular age-related macular degeneration. The reason for this change is unclear, but may relate to changes in blood flow or inflammatory changes within the retina.