Title : Low-cost documentation of Mizuo–Nakamura phenomenon in Oguchi disease using 20D lens and smartphone fundus videography: A rural feasibility case report

Background: Oguchi disease is a rare autosomal recessive form of congenital stationary night blindness characterized by the pathognomonic Mizuo–Nakamura phenomenon, a reversible golden metallic sheen of the fundus that disappears after prolonged dark adaptation. Despite its diagnostic significance, real-time documentation remains limited in resource-constrained settings.

Methods: We report a case of a young patient with lifelong nyctalopia who underwent detailed ophthalmic evaluation. Fundus findings were documented using an innovative, low-cost approach combining a 20D lens with smartphone-based fundus videography, capturing retinal changes before and after dark adaptation.

Results: Visual acuity and anterior segment examination were normal. Fundus evaluation under photopic conditions revealed a diffuse golden-yellow metallic sheen, which completely reverted to a normal reddish-orange appearance following prolonged dark adaptation, confirming the Mizuo–Nakamura phenomenon. This dynamic transition was successfully captured in real-time using 20D-assisted smartphone videography. Electroretinography demonstrated markedly reduced rod responses with preserved cone function, consistent with Oguchi disease.

Conclusion: This report demonstrates that the Mizuo–Nakamura phenomenon can be reliably documented using simple, portable, and cost-effective tools without dependence on advanced imaging systems. The ability to capture this hallmark sign in video format adds significant diagnostic and educational value.

Novelty Statement: Despite the utmost rarity, this is among the first reports demonstrating real-time videographic documentation of the Mizuo–Nakamura phenomenon using smartphone-assisted 20D imaging, highlighting its potential application in rural and low-resource settings.

Dr. Neel Kavediya is an ophthalmology resident at Madras Medical College with a strong interest in retinal diseases and clinical research. He is a founding member of “Jignyasa,” an initiative aimed at promoting research literacy among medical trainees. His work focuses on developing low-cost, practical innovations to improve ophthalmic care delivery in resource-limited settings.