The yellow arrows indicate arteriovenous crossings in which the artery lies in front of the vein. This is a frame from the midphase of a fluorescein angiogram of the inferotemporal quadrant of the retina of a normal eye. The center of the retina, called the macula, has no vessels, and is called the avascular zone. In this photo, the dye appears white as it fills the vessels. These allow the ophthalmologist to analyze the blood supply to the retina. As this dye circulates through the eye, many sequential black and white photographs are taken. In a fluorescein angiogram, approximately two tablespoons of a dye (not related to iodine containing x-ray dyes) is injected into a vein in the patient's arm. The normal ratio of diameter of a retinal vein to a retinal artery at a given distance from the center of the optic disc is approximately 1.3:1. The normal central retinal artery (black arrow) is located nasal to the central retinal vein (green arrow) in the optic disc. The macula is a circular area of diameter 5.5 mm with a center located 17 degrees, or 4.0-5.0 mm, temporal, and 0.53 - 0.8mm inferior to the center of the optic disc. The following is a fundus photograph from a normal eye showing the macula (green circle) and fovea (black circle). The red curving structures are blood vessels which enter the retina through the nerve. The whitish circle is the nerve that connects the retina to the brain. This fundus photograph shows the normal appearance of the retina. Refer to this page for comparison with the retinal disease pages. This page describes normal retinal anatomy. Normal Retinal Anatomy - The Retina Reference The Retina Reference
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