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macula lutea[′mak·yə·lə ′lüd·ē·ə]
(yellow spot), the site of the greatest keenness of vision on the retina of the eye of vertebrate animals and man. It is oval in shape and located opposite the pupil, somewhat above the point of entry of the optic nerve into the eye.
The cells of the macula lutea contain a yellow pigment. Blood capillaries are found only in the lower part of the macula lutea; in its middle part the retina becomes much thinner, forming a central depression (the fovea), which contains only photoreceptors. In most animals and in man the central depression contains only cone cells; in some deep-water fish with telescopic eyes, the central depression contains only rod cells. In birds distinguished for their sharp vision, there may be up to three central depressions. In man the diameter of the macula lutea is approximately 5mm. In the central depression the cones are rod-shaped (the longest receptors of the retina). The diameter of the area free of rod cells is 500–550 microns; it contains about 30,000 cone cells.