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Electro-oculogram

(A) Placement of electrodes for EOG recording. (B) Normal EOG recording. An electro-oculogram measures: (1) voltage potential between cornea and Bruch membrane and (2) voltage potential changes with illumination. Arden ratio, light peak: dark trough (nl >1.8). Abnormality suggests diseases that primarily affect the retinal pigment epithelium. (Contributed by Dr. James Walters.)