Stargardt Disease - Dark Choroid Sign
'You should look at the normal fluorescein angiogram first for comparison. In Stargardt Disease, lipofuscin pigment accumulates in the retinal pigment epithelium, a layer of cells underneath the retina. This blocks light transmission through the retinal pigment epithelium in taking a fundus photograph, and prevents the observer from seeing the choroidal blood vessels that are beneath the retina. When this occurs in taking a fluorescein angiogram, it is called the dark choroid sign. The atrophic macular zone of retinal pigment epithelium appears in the photograph as a white area. Because there is no retinal pigment epithelium in this area, the bright white choriocapillaris filling by fluorescein dye shows up in marked contrast to the surrounding area in which the choroidal details are blocked by intact overlying retinal pigment epithelium.