The pigment cells have cylindrical sheaths on their apical surface that are associated with, but do not directly contact, the tip of the photoreceptor processes of the adjacent rod and cone cells. Complex cytoplasmic processes project for a short distance between the photoreceptor cells of the rods and cones. Numerous elongated melanin granules, unlike those found elsewhere in the eye, are present in many of these processes. They aggregate on the side of the cell nearest the rods and cones and are the most prominent feature of the cells. The nucleus with its many convoluted infoldings is located near the basal plasma membrane adjacent to Bruch’s membrane. The cells also contain material phagocytosed from the processes of the photoreceptor cells in the form of lamellar debris contained in residual bodies or phagosomes. A supranuclear Golgi apparatus and an extensive network of smooth-surfaced  FOLDER 24.3 Clinical Correlation: Age-Related Macular Degeneration (ARMD)
Age-related macular degeneration (ARMD) is the most common cause of blindness in older individuals. Al-though the cause of this disease is still unknown, evi-dence suggests both genetic and environmental (UV irradiation, drugs) components. The disease causes loss of central vision, although peripheral vision remains unaffected. Two forms of ARMD are recognized: a dry (at-rophic, nonexudative) form and a wet (exudative, neovas-cular) form. The latter is considered a complication of the first. Dry ARMD is the most common form (90% of all cases) and involves degenerative lesions localized in the area of the macula lutea. The degenerative lesions in-clude a focal thickening of Bruch’s membrane called drusen, atrophy, and depigmentation of RPE, and obliter-ation of capillaries in the underlying choroid layer. These changes lead to deterioration of the overlying photosensi-tive retina, resulting in the formation of blind spots in the visual field (Fig. F24.3.1). Wet ARMD is a complication of dry ARMD caused by neovascularization of blind spots of the retina in the large drusen. These newly formed, thin, fragile vessels frequently leak and produce exudates and hemorrhages in the space just beneath the retina, result-ing in fibrosis and scarring. These changes are responsi-ble for the progressive loss of central vision over a short time. The treatment of wet ARMD includes conventional laser treatment therapy; however, new surgical methods such as macular translocation have been recently introduced. In this procedure, the retina is detached, translocated, and reattached in a new location, away from the choroid neovascular tissue. Conventional laser treat-ment is then applied to destroy pathologic vessels with-out destroying central vision. FIGURE F24.3.1 • Photograph depicting the visual feld in individuals with age-related macular degeneration. Note that central vision is absent because of the changes in the macula region of the retina. To maximize their remaining vision, individuals with this condition are instructed to use eccentric fixation of their eyes.
endoplasmic reticulum (sER) surround the melanin granules and residual bodies that are present in the cytoplasm. The RPE serves several important functions, including the following:  It absorbs light passing through the neural retina to prevent reflection and resultant glare.
 It isolates the retinal cells from blood-borne substances. It serves as a major component of the blood–retina barrier via tight junctions between RPE cells.
 It participates in restoring photosensitivity to visual pigments that were dissociated in response to light. The metabolic apparatus for visual pigment resynthesis is present in the RPE cells.
 It phagocytoses and disposes of membranous discs from the rods and cones of the retinal photoreceptor cells.
The rods and cones of the photoreceptor cell (layer 2) extend from the outer layer of the neural retina to the pigment epithelium.