Contributor: Gordon K. Klintworth
The term drusen (German Druse = stony nodule) is used for two distinct lesions in the optic nerve (common drusen [drusen - common] and giant drusen [drusen - giant]) and for deposits on Bruch membrane [drusen - retina]. The giant drusen of the optic nerve are found almost entirely in persons with tuberous sclerosis. Drusen on Bruch membrane can be either nodular [drusen - nodular], diffuse [drusen - diffuse], or soft [drusen - soft]. They occur in aging, age-related macular degeneration, in degenerations of the retina and choroid, and as an autosomal dominant primary dystrophy [drusen - dominantly inherited]. On examination, drusen look like small, bright, sharply demarcated lesions under the retinal vessels. They are most common in the posterior pole. They may coalesce and have pigmented edges. Patients may complain of some  metamorphopsia. Basal laminar drusen [drusen - basal laminar]) are innumerable, small and uniformly sized yellow subretinal lesions, best seen with fluorescein angiography, in which they hyperfluoresce brightly and early. They are distinguished from typical soft drusen by semitranslucency seen in retroillumination biomicroscopy, as opposed to opaque appearance of soft drusen. Soft drusen are also more variable in size and appear less hyperfluorescent on fluorescein angiography than basal laminar drusen.