The dark choroid in posterior retinal dystrophies.

Many patients with heredomacular degeneration exhibit a peculiar fluorescein angiographic finding of absence of the normal background fluorescence (a dark choroid). The cause of this is unknown but may relate to the deposition of an abnormal material in the retinal pigment epithelial cells. The finding does not correlate with severity or duration of disease but is more frequent in patients with flecks. The finding may be useful in subdividing heredomacular degenerations into more specific disease groups.