# Throwing light on night blindness associated with rare manifestation of vitamin A deficiency

## TL;DR

A 38-year-old man with vitamin A deficiency showed a rare eye condition called the Mizuo phenomenon, highlighting the link between low vitamin A and night blindness.

## Contribution

This is the first reported case of the Mizuo phenomenon associated with vitamin A deficiency and normal ERG but abnormal EOG.

## Key findings

- The patient exhibited a metallic sheen in the retina, which disappeared after dark adaptation, consistent with the Mizuo phenomenon.
- Multimodal imaging showed retinal thinning and hyperautofluorescent flecks, but ERG was normal while EOG was abnormal.
- Vitamin A supplementation did not significantly improve serum levels, suggesting a need for further study on treatment efficacy.

## Abstract

This case report describes a rare presentation of the Mizuo phenomenon in a vitamin A deficiency-associated patient.

A 38-year-old male presented with nyctalopia for 10 years and a fresh onset of dry eyes. He was a known case of alcoholic liver disease with cirrhosis and Oguchi disease. Anterior segment evaluation revealed moderate dry eyes, and fundus examination revealed metallic sheen OU, the latter extinguished after dark adaptation via a modified patch test suggestive of the Mizuo Nakamura phenomenon. Multimodal imaging modalities like SD-OCT, short-wave autofluorescence, and electrophysiological tests were performed. Findings suggested a diagnosis other than Oguchi’s disease. The gene panel comprising SAG and GRK1 mutations was negative for Oguchi. Serum vitamin A levels were significantly low (0.03 mg/l). The patient was started on topical lubricants and oral vitamin A supplements and counseled to abstain from alcohol.

SD-OCT demonstrated thinning of the ellipsoid region with multiple hyperreflective excrescences in outer retinal layers colocalized with hyperautofluorescent flecks on short-wave autofluorescence. ERG was normal bilaterally. An electrooculogram showed a significantly decreased Arden ratio of OU. After controlled oral Vitamin A supplementation, the patient’s serum Vitamin A levels remained low (0.06 mg/l).

This case is rare and likely the first reported presentation of the Mizuo phenomenon in a vitamin A deficiency-associated patient with normal ERG and abnormal EOG. Increasing choice for weight loss diet and bariatric surgeries Vitamin A deficiency is also expected to affect developed countries. Modified patch tests make diagnosis easier and earlier. More extensive studies are needed to correlate levels of Vitamin A with the natural course of the Mizuo phenomenon and substantiate multimodal imaging findings.