Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 59

The RPE is a monolayer of flat, polygonal cells that forms the outermost layer of the retina. It is the continuation of the outer pigmented epithelial layer of the ciliary body. The RPE is more adherent to the choroid than to the rest of the retinal tissue, and it serves an important role in nutrient transport from the choriocapillaris to the outer layers of the retina. Each cell sends cytoplasmic processes inward to surround the photoreceptor outer segments, which help to filter out excessive amounts of light and increase the photoreceptors' individual sensitivity. They also phagocytize the outer segments of photoreceptors as they are continuously shed. The RPE cells are usually densely pigmented, but there is variability in the intensity of pigmentation among individual animals.

Figure 1.53 The retina consists of nine discrete layers and a supportive pigmented epithelium that forms an outer, tenth layer, as demonstrated by light microscopy in the dog. G, ganglion cell; 1, RPE; 2, photoreceptor layer; 3, outer limiting membrane; 4, outer nuclear layer; 5, outer plexiform layer; 6, inner nuclear layer; 7, inner plexiform layer; 8, ganglion cell layer; 9, nerve fiber layer; 10, inner limiting membrane. The outer and inner limiting membranes are denoted by dashed lines.