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AIM—To describe the early formation of drusen and their relation to normal aging changes at the macula and to the development of age related maculopathy (ARM).
METHOD—Histopathological features of 353 eyes without histological evidence of ARM are described and correlated with the clinical appearance. In addition, 45 of these eyes were examined by transmission electron microscopy.
RESULTS—Drusen were detected histopathologically in 177 (50%) eyes but were seen clinically in only 34% of these. Drusen were mainly small hard drusen with an occasional soft distinct drusen: no soft indistinct drusen were seen. Only those drusen deposits larger than 25-30 µm in diameter were detectable clinically. Preclinical drusen in eyes with only an occasional drusen were seen on electron microscopy as entrapment sites of coated membrane bound bodies which formed adjacent to the inner collagenous zone of Bruch's membrane. In contrast, preclinical drusen deposits in eyes with many drusen were seen as accumulations of amorphous material which appeared hyalinised by light microscopy. A distinct feature were rows of dense hyalinised microdrusen (1-2 µm in diameter), over which larger globular hyalinised drusen formed.
CONCLUSION—Histological and ultrastructural examination can recognise and distinguish the earliest drusen formed as a result of normal aging from those associated with ARM. In eyes without diffuse deposits, histologically all drusen were of the hard hyalinised variety or their derivatives; no soft drusen composed of membranous debris were found. These findings support and explain those of other authors who do not consider the presence of a few small hard drusen to be a risk factor for the development of ARM.
Keywords: aging; macular degeneration; retinal drusen; entrapment