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Disease

Drusen

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DrusenThe small yellow-white spots are drusen. There are many in this eye, as you can see by comparing this photo to the normal eye, above.

Drusen are tiny yellow or white accumulations of extracellular material that build up in Bruch's membrane of the eye. The presence of a few small ("hard") drusen is normal with advancing age, and most people over 40 have some hard drusen. However, the presence of larger and more numerous drusen in the macula is a common early sign of age-related macular degeneration (ARMD). Drusen associated with aging and macular degeneration are distinct from another clinical entity, optic disc drusen, which is present on the optic nerve head. Both age-related drusen and optic disc drusen can be observed by ophthalmoscopy.

Whether drusen promote ARMD or are symptomatic of an underlying process that causes both drusen and ARMD is not known, but they are indicators of increased risk of the complications of ARMD.

The source of the proteins and lipids in drusen is also not clear, with potential contributions by both the RPE and the choroid. Several trace elements are present in drusen probably the most concentrated being zinc. The protein composition of drusen includes apoliproteins and members of the complement system. Zinc in drusen have been suggested to play a role in drusen formation by precipitating and inhibiting the elemts of the complement cascade, especially complement factor H. The presence of molecules that regulate inflammation in drusen has led some investigators to conclude that these deposits are product of the immune system.