What retinal physiology test is abnormal in Best's disease?

The abnormality in Best's disease is most clearly indicated by the results of the Electrooculogram (EOG). In Best's disease, there is a defect in the RPE (retinal pigment epithelium) function, which leads to decreased values of the EOG. The EOG measures the electrical potential between the front and back of the eye, and in patients with Best's disease, the Arden ratio (the standard measurement derived from the EOG) is often reduced, reflecting the RPE dysfunction.

Other tests, while they may show changes associated with Best's disease, do not specifically indicate the condition as directly as the EOG does. The Electroretinogram (ERG), for instance, assesses the overall function of the photoreceptor cells and may not be as significantly altered in the earlier stages of Best's disease. Optical Coherence Tomography (OCT) can reveal structural changes in the retina, and Fundus Photography illustrates the appearance of the retina, including the characteristic yellowish lesions, but these tests do not directly reflect the impaired electro-physiological activity of the retina as the EOG does. Thus, the EOG is the most relevant test in diagnosing and understanding the physiological abnormalities associated with Best's