The macula is an oval-shaped pigmented area in the center of the
retina of the
human eye and other animal
eyes. Its center is shifted slightly away from the
optical axis (laterally, by 5°=1.5 mm). The macula in humans has a diameter of around and is subdivided into the
umbo,
foveola,
foveal avascular zone,
fovea,
parafovea, and
perifovea areas. The anatomical macula at is much larger than the clinical macula which, at , corresponds to the anatomical fovea. The umbo is the center of the foveola which in turn is located at the center of the fovea. The fovea is located near the center of the macula. It is a small pit that contains the largest concentration of
cone cells. The retina's receptor layer contains two types of photosensitive cells, the
rod cells and the cone cells.
Color Because the macula is yellow in color, it absorbs excess blue and ultraviolet light that enter the eye and acts as a natural sunblock (analogous to sunglasses) for this area of the retina. The yellow color comes from its content of
lutein and
zeaxanthin, which are yellow
xanthophyll carotenoids, derived from the diet. Zeaxanthin predominates at the macula, while lutein predominates elsewhere in the retina. There is some evidence that these carotenoids protect the pigmented region from some types of
macular degeneration. A formulation of 10
mg lutein and 2 mg zeaxanthin has been shown to reduce the risk of age-related macular degeneration progressing to advanced stages, although these carotenoids have not been shown to prevent the disease. After death or
enucleation (removal of the eye), the macula appears yellow, a color that is not visible in the living eye except when viewed with light from which red has been filtered.
Regions •
Fovea – •
Foveal avascular zone (FAZ) – •
Foveola – •
Umbo – ==Function==