The foveal avascular region of developing human retina

Objective: To study the development of the perifoveal retinal vasculature. Methods: We studied 7 retinas aged between 26 weeks' gestation and 1 week postnatal (41 weeks' gestation). Sections were imaged using high-resolution digital photography and blood vessel profiles identified at 200% to 300% magnification. Flat mounts were immunolabeled using antibodies to CD31 and factor VIII to identify blood vessels and antibodies to rhodopsin to identify the rod-free zone. Results: The foveal region was identified by the absence of rod photoreceptors in the outer retina and/or presence of a shallow depression in the inner retina. The whole mount at 26 weeks' gestation showed a blood vessel-free region centered on the rod-free zone that was open along the horizontal meridian on the temporal side. At 37 weeks' gestation, the foveal avascular zone formed a complete circle. In sections, the foveal avascular zone was approximately 500 μm in diameter at 35 weeks' gestation and 300 to 350 μm at 40 weeks' gestation; in whole mounts, it was 150 to 170 μm in diameter at 37 and 41 weeks' gestation. Conclusions: The foveal region is normally avascular during development, as in adult life. We found no evidence of foveal vascularization during development of the human retina. Clinical Relevance: Instances of vascularization of the foveal region are not due to failed regression of a transient vasculature.