Histological findings of uveal capillaries in rabbit eyes after multiple intravitreal injections of bevacizumab.

Purpose: To evaluate the potential toxicity of multiple intravitreal injections of bevacizumab on the uveal capillaries of rabbit eyes. Materials and methods: Nine eyes of nine rabbits that received single intravitreal injections of bevacizumab (IVB) constituted the single IVB group, while nine eyes of nine rabbits that received three injections of IVB, with an interval of 28 days between injections, constituted the repeat IVB group. Seven eyes of seven rabbits constituted the control group. The rabbits in the single and repeat IVB groups were sacrificed 7 and 28 d after the single and third IVB injection, respectively. Uveal specimens were compared between groups after immunohistochemical staining. Ultrastructural findings were evaluated by electron microscopy. Control group rabbits were sacrificed 7 d after saline injection. Clinical examination and fundus fluorescein angiography were performed at baseline, 7 d after the first injection, and after the last injection. Results: Differences in the CD31-positive areas of the iris, ciliary body and choroid 7 d after IVB were not statistically significant among the single IVB, repeat IVB and control groups (p = 0.0749, p = 0.7237 and p = 0.7346, respectively; analysis of variance). Endothelial cell fenestrations (ECFs) in the choriocapillaris and ciliary body observed by electron microscopy on day 7 in the single and repeat IVB groups were decreased by 50% (p < 0.0001) and 33% (p < 0.0001), respectively, in both IVB groups compared with those in the control group. However, ECFs observed on day 28 in both groups were comparable to those observed in the control group. Conclusions: Single IVB and repeated IVB did not have any effect on normal vessel endothelium density as per immunohistochemical findings. Ultrastructural findings revealed that IVB transiently decreased the ECFs in the choriocapillaris and ciliary body.