<prompt> Best disease due to a mutation in the BEST1 VMD2 is best diagnosed by a pathological:ERGEOGDark adaptationOhoptoscope  <response>: Best Disease Juvenile-Onset Vitelliform Dystrophy: It is an autosomal dominant disorder with variable penetrance and expressivity. Onset is usually in childhood. The fundoscopic appearance is a mild pigmentary disturbance within the fovea to the typical vitelliform or egg yoke lesion located in the central macula. Visual acuity often remains good, and the ERG is normal. An abnormal electro-oculogram EOG is the hallmark of the disease. Ref: Fletcher E.C., Chong N., Augsburger J.J., Correa Z.M. 2011. Chapter 10. Retina. In P. Riordan-Eva, E.T. Cunningham, Jr. Eds, Vaughan Asburys General Ophthalmology, 18e. 