A woman in her 40s had nonprogressive nyctalopia since childhood. Her best-corrected visual acuity was 20/20 OU. The results of examinations of the anterior segment, intraocular pressure, color vision, and visual field were normal. The results of a fundus examination revealed a golden-yellow reflex in both eyes (Figure, A). After 3 hours of dark adaption, the reflex disappeared (Mizuo-Nakamura phenomenon) (Figure, B). This color change is thought to be caused by an excess of extracellular potassium in the retina due to a decreased potassium scavenging capacity of retinal Müller cells.1,2 The color change is commonly associated with X-linked retinoschisis, X-linked recessive cone dystrophy, and Oguchi disease.3-5 The patient underwent electroretinography, which revealed generalized rod dysfunction with a normal cone response. Her clinical and imaging findings led to a diagnosis of Oguchi disease, and the patient was observed. The Mizuo-Nakamura phenomenon has been observed in this patient in 3 different dark adaption tests during a 2-year follow-up period.
Pellerano F, Gonzalez M, Alvarado A. Mizuo-Nakamura Phenomenon in a Middle-aged Woman. JAMA Ophthalmol. 2018;136(9):e182640. doi:10.1001/jamaophthalmol.2018.2640
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