The fovea centralis ( fovea ), one in the center of the so-called yellow spot ( macula lutea ), this depression ( in humans ~ 1.5 mm diameter), is the area of sharpest vision of the retina in mammals.
The fovea is about 5 ° temporal to the anatomical axis. It contains no rods for night vision, but about 140,000 cones per mm2 for color perception, mainly M-cones for the green region of the visible light and L- cones for the red zone, where the total number of cones on the retina from 3.3 to 7 million cones located. These two pin varieties are particularly slim built and placed in the fovea in a uniform mosaic. In the innermost region of the foveola ( in humans ~ 0.33 mm in diameter), only M and L cones are present, but no S-cones more ( for the blue area). The foveola is the reference point of the relative localization is the subjective center and the oculomotor zero and simultaneously represents the main Ehrich Tung " straight ".
An object is always so fixated by the eye that are more accurate to be detected parts of the object come in succession to lie in the fovea ( see figure below peripheral vision ).
Due to the absence of rods and the related inability to perceive finer structures in low light conditions, it is hard to read, for example a text in low light conditions.
The fovea has a convergence of 1:1, that is, on each receptor followed by a ganglion cell. The receptors are therefore connected 1:1. This is in the fovea centralis the highest resolution, so achieved the greatest visual acuity. Therefore, the foveal system works as an extremely powerful telephoto lens with simultaneous macro function.
The remaining area of the retina is the peripheral vision. This corresponds to an extreme wide -angle lens that delivers a ganglion cell as a result of his blur and the interconnection of multiple receptors each an overall impression.
Actual images are created but not yet on the retina to the visual center of the brain. The many individual visual impressions of both systems are processed together with memory images without any delay to a perception.