Saturday, October 22, 2005

Macula and Fovea

The macula, area centralis, has a diameter of about 5.5 mm and is defined histologically by the presence of more than 1 layer of ganglion cells. Clinically one uses the presence of yellow carotenoid pigments that are present in Henle's layer to identify the macula. The correlation is not perfect however than the clinical definition is not as precise as the histologic one.

The fovea is a depression in the center of the macula that measures about 1.5 mm in diameter. The center of the fovea (foveola) resides usually about 4.0 mm temporal and 0.8 mm inferior to the optic nerve head. There are no ganglion cells in the fovea but only glial cells and Muller cells in the area of the fovea referred to as the foveola which measures about 350 microns in diameter. There is a foveal avascular zone or capillary-free zone that is about 400 microns in diameter.


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