Correlation between clinical and histological features in a pig model of choroidal neovascularization

Purpose: To analyse the histological changes in the retina and the choroid in a pig model of choroidal neovascularization (CNV) and to correlate these findings with fundus photographic and fluorescein angiographic features. Methods: CNV was induced by surgical removal of the retinal pigment epithelium (RPE) and perforation of Bruch's membrane in four pig eyes. In addition, two eyes had an amniotic membrane implanted in the subretinal space. Retinal landmarks such as arterioles, crossing of vessels and the optic nerve were used to obtain an exact mapping of histological findings on colour fundus photographs (FPs) and fluorescein angiograms (FAs). We analysed the appearance on the FPs and FAs of the following histological features: CNV, hypo/hyperpigmented RPE, and pathological changes to the retina and choroid. Results: CNV was found in all eyes and correlated to areas with late staining but no leakage in the FAs. Areas of hypopigmented RPE were identified and corresponded to window defects in the FAs. Where fibrovascular tissue was covered with hyperpigmented RPE, blocked fluorescence was found on the FAs. The implanted amniotic membrane showed staining but no leakage in the FAs. Conclusion: In a pig model of surgically induced CNV, histological mapping was used to make clinicopathological correlations of the following lesion components: CNV, window defects, blocked fluorescence. Our findings give a more solid foundation for interpretation of fluorescein angiograms in pig models.