Recurrence of macular edema in eyes with branch retinal vein occlusion changes the diameter of unaffected retinal vessels

Purpose: To measure unaffected retinal vessel diameter in eyes with macular edema (ME) secondary to branch retinal vein occlusion (BRVO) after intravitreal injection with bevacizumab (IVB). Methods: Patients with BRVO-induced ME who responded to IVB were assessed at baseline and 1, 3, and 6 months. In both eyes, the diameters of the largest arteriole and venule in all quadrants (except occlusion quadrant) were measured by using a computer-assisted method. The same vessels chosen at baseline were measured at each follow-up examination. Results: Forty-two eyes were participated. At baseline, venular diameters of unaffected quadrants in eyes with BRVO were larger than the venules in the corresponding quadrant of the fellow eyes (p < 0.05, respectively). The venular diameters in all quadrants of the affected eyes decreased significantly relative to baseline after IVB (p < 0.05 respectively). Twenty-two eyes (52.4 %) developed recurrent ME. On recurrence at 3 (n = 15, 35.7 %) or 6 months (n = 7, 16.7 %), the unaffected venular diameters increased significantly (p < 0.05 respectively). These diameters again decreased significantly after a second IVB (p < 0.05 respectively). Conclusion: Unaffected retinal venular diameters associate with the course of BRVO with ME. This may help elucidate the pathological mechanism underlying BRVO.