Figure 1. Adult and fetal human retinas. A: Image showing the fundus of an adult human eye with the optic disc (OD), the macula (broken circle) and the location of the fovea centralis (asterisk) indicated. The large retinal vessels extend from the optic disc into the supero-temporal and infero-temporal retina (white arrows), but do not grow directly toward the macula. Only fine caliber vessels are present in the macula. B: High power micrograph showing microvessels (black arrows) surrounding the fovea centralis in a retinal flatmount. The fovea is a shallow depression, <1 mm in diameter, in the surface of the retina, located at the center of the macula, and centered on an avascular area 500–700 μm in diameter. Absence of capillaries at the fovea ensures that the highest quality image possible reaches the photoreceptors. C: A diagram of a flatmounted human fetal retina at 19 WG showing the vascularized region of the retina at this stage in gray, and the location of the fovea (asterisk). The two circles indicate the approximate size and location of biopsies taken from nasal and temporal retina, and used for RNA extraction for this study. RNA was also extracted from the remainder of the retina (surround).