Background: To compare effects of multiple injections of small divided doses of intravitreal bevacizumab vs a single injection using a retinal neovascular model in rabbits.
Methods: We assigned 12 pigmented rabbits to four groups of three each. All groups received an intravitreal injection of vascular endothelial growth factor (VEGF, 10 microg) on the first day. Group A received an intravitreal loading dose of bevacizumab (0.5 mg) on day 3, followed by five smaller injections (0.15 mg), one every third day. Those in groups B and C received a single intravitreal injection of bevacizumab (1.25 mg) on day 3, followed by five injections of sham, one every third day in group C. Group D received only intravitreal VEGF. Follow-up examinations were performed for 26 days.
Results: In groups A and B, vascular changes associated with VEGF injection decreased substantially in the first 3 days, and continued to show gradual regression during each follow-up interval. No statistically significant differences were found between the changes of mean retinal thicknesses in groups A and B in both areas. In group C, the extra sham injections did not lead to any further vascular changes. The mean retinal thickness in groups B and C did not have a statistically significant difference during the follow-up period. In group D, vascular changes resolved more gradually than in other groups. The difference in retinal thickness between group D and the other groups was statistically significant on day 6 in both groups (medullary and inferior part; p = 0.0003) and in medullary wing on day 12 (p = 0.03).
Conclusions: Frequent smaller doses of bevacizumab can control VEGF-induced vascular changes as well as the currently utilized model of single large monthly injections. Dividing of currently used single injection (1.25 mg) of bevacizumab to multiple small doses can control VEGF-induced vascular changes as effectively as one large injection.