Think It's AMD? Think AgainMark T. Dunbar, O.D.
A 64-year-old white male was referred by his optometrist for a retinal
evaluation. The patient had received a diagnosis but could not remember
the name. He was in good health and could recall no specific family history
of eye problems. He did say that his older brother had a problem with one
of his eyes as a child.
Best-corrected visual acuity was 20/25 in each eye. Confrontation fields were full to careful finger counting. The pupils were equally round and reactive and there was no afferent pupillary defect. Amsler grid testing showed minimal central metamorphopsia in each eye. The anterior segments displayed nothing of interest.
A dilated fundus exam showed healthy optic nerves with a small cup and
good rim coloration and perfusion O.U. The macula of each eye exhibited
obvious changes, as you can see in the fundus photos.
Based on the pattern of pigment distribution in the macula, this disease has been subdivided into five principle groups:
Group 2: butterfly-shaped pigment dystrophy.
Group 3: reticular dystrophy of the RPE.
Group 4: multifocal pattern dystrophy simulating fundus flavimaculatus.
Group 5: fundus pulverulentus.
Patients with a butterfly-shaped pattern dystrophy will have gray or yellow pigment in a well-organized triradiate pattern. With reticular dystrophy, the pattern extends into the periphery. Here too the yellow pigment is highly organized, in a manner resembling the knotted configuration of a fishnet or chicken wire. Those with multifocal pattern dystrophy simulating fundus flavimaculatus develop triradiate flecks similar to those of Stargardt's disease; but these patients don't show angiographic evidence of a dark choroid suggesting a lipofuscin storage disease. Finally, patients with fundus pulverulentus display prominent, coarse, "punctiform" mottling of the RPE in the macular area.
So which pattern dystrophy does our patient have? It's Group 1, adult-onset foveomacular vitelliform dystrophy. These patients generally present with a solitary yellow subretinal lesion that's symmetric, round and slightly elevated. It's usually about 0.333-1 disc diameter in size. There's often a pigmented spot in the center. Initially the yellow lesion may develop only in one eye. Most of the vitelliform lesions in this condition are small, but the larger ones can look identical to the "sunny-side-up" stage of Best's vitelliform macular dystrophy. These can also look quite similar to bilateral serous detachments of the RPE from AMD.
In differentiating Best's disease from these adult vitelliform lesions, remember that the vitelliform lesions in Best's develop in infancy or early childhood. Further, genetic linkage studies have identified Best's disease to chromosome 11q13. Attempts to identify common genetic linkage between Best's disease and other vitelliform macular dystrophies have been unsuccessful.
The prognosis for maintaining good vision is excellent. The elevated foveal lesions generally fade and leave an irregular oval or round area of RPE depigmentation. The lesions generally do not show the sort of disruption and layering of the yellow pigment that you see with Best's vitelliform lesions. Choroidal neovascularization may occur, but it's rare.
|© Review of Optometry OnLine
May 15, 2000