Computerized Morphometry to Quantify Choroidal Vasodilation in an Animal Model of Choroidal Neovascularization

Abstract

Abstract: : Purpose: Drug treatment for choroidal neovascularization (CNV) is currently designed to counteract the effects of growth factor–induced neovascularization and leakage. An early and prominent effect is vasodilation, a response that has previously been reported (ARVO, 2003) in the choroidal vasculature after suprachoroidal implantation of a hydron pellet containing VEGF and bFGF in rabbits. Quantitation of this phenomenon would enable gauging the response to drug therapy and more effectively screen drugs for clinical trials. Methods: One month following suprachoroidal implantation of a hydron pellet containing 20ug of VEGF and 20ug of bFGF matched with control subject blank pellets, Dutch Belt rabbits were euthanized, eyes enucleated, and prepared for histologic evaluation. Computerized digital morphometry image analysis was used to measure the cross–sectional area of the choroidal vessels and calculate the cross–sectional area ratio between choroidal vessels/ choroid. The results in an experimental eye were compared to a control eye and differences evaluated with paired and unpaired Student’s t–test to the 99% confidence interval. Results: There was considerable vasodilation in the choroid in the presence of the pellet containing VEGF and bFGF. The cross sectional area of the choroidal vasculature was 45.56 % of the entire choroid in the presence of growth factors, as compared to 0.95 % in the control eye (double–sided pvalue = 1.89x10^–7). Conclusions: This semi–automated, computerized methodology accurately quantitates the degree of choroidal vasodilation induced by intraocular growth factors. Such a quantitative outcome measure in an animal model can be very useful to screen candidate drugs with putative anti–angiogenic properties, so as to more effectively select drugs for extensive clinical trials.

Keywords: choroid: neovascularization • growth factors/growth factor receptors • imaging/image analysis: non–clinical