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P. Gouras, L. Ivert, J. Mattison, M. Neuringer; Drusenoid Retinopathy in Rhesus Monkeys (Macaca Mulatta) . Invest. Ophthalmol. Vis. Sci. 2006;47(13):856.
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To determine whether drusenoid changes in older monkeys resembles age related macular degeneration in man.
Biomicroscopy, fundus photography and angiography were used to examine monkeys, 1 to 39 years of age, a large fraction maintained on strict dietary regimens. Clinical findings were correlated with post mortem light and electron microscopy.
Drusenoid retinopathy was seen in 37% (36/97) under and 57% (20/35) over 20 years of age. Severity also increased with age. The drusen were often wide–spread across the posterior pole but tended to increase in number and size toward the macula. Histology showed the drusen to be symmetrical detachments of the retinal epithelium and basal lamina from Bruch’s membrane. Their diameters range from 5 to 300 microns, the latter being large serous detachments of the epithelium. Many were too small to detect clinically. All were filled with amorphous material but often remnants of retinal epithelial cells were found. In small drusen, the detached epithelium appeared normal; in large ones, atrophy, displacement, and occasionally lipoidal degeneration of the epithelium were found. Above, even the largest drusen, degeneration of the outer nuclear layer was absent but adjacent outer segments were shortened and disoriented. So far, no foreign cells or evidence of inflammation have been found in the vicinity of drusen. There was thickening and calcification of the remainder of Bruch’s membrane in the older monkeys but choroidal vessels were normal. There was no evidence of geographic atrophy or neovascularization. Some monkeys had no drusenoid retinopathy even at advanced age.
Drusenoid retinopathy is a common affliction in monkeys and resembles human age related maculopathy in all but its most severe stages. The presence of normal epithelium elevated by bilaterally symmetrical dome shaped detachment of the basal lamina from the collagen layer of Bruch’s membrane implies a weakness at this point vulnerable to cleavage. Striking differences in the incidence of this abnormality among monkeys of similar age suggest that genetic factors are involved.
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