Optic fovea

Image:Schematic diagram of the human eye.png

The fovea, a part of the eye, is a spot located in the center of the macula. The fovea is responsible for sharp central vision, which is necessary in humans for reading, watching televisionor movies, driving, and any activity where visual detail is of primary importance.

At the center of the fovea there is a pit with a diameter of about 0.2 mm. It has a high concentration of cone cellsand virtually no rods. Compared to the rest of the retina, the cones in the foveal pit are smaller and more densely packed (in a hexagonalpattern), and they are not obscured by a layer of nerve cells or blood vessels; all of this together accounts for the sharp vision associated with them. The fovea is largely responsible for the color visionin humanswhich is superior to most other mammals.

The foveal pit is not located exactly on the optical axis; it is displaced about 4 to 8 degrees temporal to the optical axis.

Surrounding the foveal pit is the foveal rim, where the neurons displaced from the pit are located. This is the thickest part of the retina.

Since the fovea does not have rods, it is not sensitive to dim lights. Astronomersknow this: in order to observe a dim star, they use peripheral vision, looking out of "the side of their eyes".

The fovea is covered in a yellow pigment called xanthophyll. This absorbs blue light and is probably an evolutionary adaption to the problem of chromatic aberration.

es:Fóvea

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It uses material from the http://en.wikipedia.org/wiki/Optic+fovea Wikipedia article Optic fovea.