Authors : Nischala Balakrishna, Alhaj F Tasneem, Vittal I Nayak, Nagalakshmi Narayanaswamy, Sara Nastain
DOI : 10.18231/j.ijceo.2020.141
Volume : 6
Issue : 4
Year : 2020
Page No : 660-663
Introduction: Oguchi disease also called congenital stationary night blindness is an autosomal recessivegenetic condition first identified in Japan with a few cases reported in other countries like Europe, America, India and Pakistan. We report one such case exhibiting the Mizuo-Nakamura phenomenon with a reduced amplitude on the b-wave of the rod electroretinogram advocating this diagnosis.
Case Report: A 40-year-old man presented with complaints of non-progressive decrease in vision as the day progressed for 6 months with normal vision during the day in both eyes. There was no history of trauma or any other ocular or systemic disease. His parents had a second-degree consanguineous marriage and his father experienced similar symptoms. Visual acuity for distance was 6/6 and N6 for near in both eyes. His anterior segment and posterior segments were normal. When the patient was put to dark adaptation for 3 hours, there was a change in his fundus background colour from grey to red (Mizuo-Nakamura phenomenon). The b-wave amplitude was decreased on the rod electroretinogram. The cone electroretinogram on the other hand was normal. All this was confirmed by his genetic study which favoured this diagnosis.
Conclusion: This disease presents with features similar to retinitis pigmentosa in terms of mutations in the SAG gene. This highlights the importance of the Mizou-Nakamura phenomenon in formulating a confirmatory diagnosis and treatment protocol.
Keywords: Congenital stationary night blindness, Mizuo-Nakamura phenomenon, Oguchi disease, Rod electroretinogram.