Specialized Regions Of The Retina

The fovea appears as a shallow depression located at the posterior pole of the optical axis of the eye. Its central region, known as the fovea centralis, is about 200 /xm in di ameter. Except for the photoreceptor layer, most of the layers of the retina are markedly reduced or absent in this region (see Fig. 23.6). Here, the photoreceptor is composed entirely of cones that are longer and more slender and rodlike than they are elsewhere. The adjacent pigment epithelial cells and choriocapillaris are also thickened in this region.

The macula lutea is the area surrounding the fovea. It is yellowish due to the presence of yellow pigment (xantho-phyll). Retinal vessels are absent in this region. Here, the retinal cells and their processes, especially the ganglion cells, are heaped up on the sides of the fovea so that light may pass unimpeded to this most sensitive area of the retina.

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