The abnormality is in the RPE, as noted on histopathology and electrophysiology testing. Fluorescein angiogram reveals blockage of choroidal fluorescence by the vitelliform lesion. The angiogram is otherwise normal at this stage. In the atrophic stage, a transmission defect is noted. If a choroidal neovascular membrane develops, then a corresponding area of hyperfluorescence with leakage will be found.
Fundus photography is useful for documentation and follow-up of fundus lesions.
The EOG, which reflects RPE function, is the most diagnostic test for evaluating vitelliform macular dystrophy. No correlation exists between EOG result and disease stage, visual acuity, or patient age. EOG results are usually symmetric for both eyes. The EOG is very useful for distinguishing this diagnosis from its differential. The EOG usually is normal in adult foveomacular dystrophy.