Alterations in Retinal Vessel Diameters in Patients with Retinal Vein Occlusion before and after Treatment with Intravitreal Ranibizumab

Purpose: To investigate the alterations of retinal vessel diameters in patients with macular edema secondary to retinal vein occlusion (RVO), before and after treatment with intravitreal ranibizumab. Methods: Digital retinal images were obtained from 16 patients and retinal vessel diameters were measured before and three months after treatment with intravitreal ranibizumab with validated software to determine central retinal arteriolar and venular equivalents, as well as arteriolar to venular ratio. Results: In 17 eyes of 16 patients with macular edema secondary to RVO (10 with branch RVO and 6 with central RVO) aged 67 +/- 10.2 years, we found that diameters of both retinal arterioles and venules were significantly decreased after intravitreal ranibizumab treatment. Specifically, the central retinal arteriolar equivalent was 215.2 +/- 11.2 mu m at baseline and 201.2 +/- 11.1 mu m at month 3 after treatment (p < 0.001), while the central retinal venular equivalent was 233.8 +/- 29.6 mu m before treatment versus 207.6 +/- 21.7 mu m at month 3 after treatment (p < 0.001). Conclusions: A significant vasoconstriction in both retinal arterioles and venules in patients with RVO was found at month 3 after intravitreal ranibizumab treatment compared to baseline. This could be of clinical importance, since the degree of vasoconstriction might be an early marker of treatment efficacy, compatible with the idea that hypoxia is the major trigger of VEGF in RVO. Further studies should be conducted to confirm our findings.