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Simulate Oguchi disease — a rare autosomal recessive form of congenital stationary night blindness (CSNB) characterised by two unique features absent in other retinal disorders: (1) complete, non-progressive scotopic failure from birth (inability to see in dim light); and (2) the pathognomonic Mizuo-Nakamura phenomenon — a striking golden/silver-grey metallic sheen visible across the entire fundus in the light-adapted state that slowly disappears after 2–12 hours of continuous darkness, revealing a near-normal fundus, and reappears rapidly on re-exposure to light. Oguchi disease is caused by loss-of-function mutations in either SAG (S-antigen / arrestin, chromosome 2q37.1), which normally terminates the phototransduction cascade by binding to phosphorylated activated rhodopsin to prevent continued G-protein stimulation in the dark; or GRK1 (G-protein–coupled receptor kinase 1 / rhodopsin kinase, chromosome 13q34), which initiates rhodopsin inactivation by phosphorylating photoactivated rhodopsin at multiple serine/threonine residues, marking it for arrestin binding. Without functional SAG or GRK1, photoactivated rhodopsin persists in a constitutively active phosphorylated (GRK1-deficient) or unquenched (SAG-deficient) state in darkness — maintaining continuous downstream phototransduction activation (constitutive transducin → phosphodiesterase → cyclic GMP hydrolysis → closed cGMP-gated channels) that mimics a permanently light-adapted state in the rod photoreceptors. This means rods are constitutively "exhausted" — perpetually in a post-bleach recovery state — and cannot respond to further low-intensity scotopic stimulation. Long periods of dark adaptation (2–12 hours) allow the phototransduction cascade to eventually exhaust and partially normalise, explaining the Mizuo-Nakamura reversal of the golden fundus appearance after prolonged darkness. Photopic (cone-driven) vision is entirely normal — cones use different kinase/arrestin homologues (GRK7/cone arrestin) unaffected by SAG or GRK1 deficiency. Model three clinical states: classic Oguchi in the light-adapted state (golden fundus sheen, absent scotopic function), prolonged dark adaptation recovery (Mizuo-Nakamura reversal in progress, partial rod recovery attempted), and a rare variant with mild cone involvement in older patients.

Oguchi disease colour science simulation by Auric Artisan.

Base color
Oguchi state & clinical setting
Scotopic deficit / severity 50%
Image simulation
Upload JPG/PNG (max 1200 × 1200). See how a scene appears through the scotopic signal loss of Oguchi disease: light-adapted state (normal daytime vision but absent rod function), prolonged dark adaptation recovery (partial rod function emerging after 2-12 hours darkness), and the rare variant with mild cone involvement. Note: photopic (daytime) vision is normal in classic Oguchi — this simulation focuses on the scotopic rod pathway deficit.
Research notes
Clinical significance of Oguchi disease: First described by Chūta Oguchi in 1907 in Japan, Oguchi disease is the archetypal form of CSNB with a recognisable fundus sign. It is more prevalent in East Asian populations (Japan, Korea, China) but has been reported in all ethnicities following identification of the causative genes. The Mizuo-Nakamura phenomenon (described by Mizuo in 1913 and Nakamura who first characterised its temporal reversal) is the only known fundus appearance that dynamically changes with the adaptation state — making it pathognomonic for Oguchi disease and uniquely useful for differentiating it from other forms of CSNB (including complete CSNB from CACNA1F, CACNA1A, or NYX mutations and incomplete CSNB). The stationary nature (non-progressive) distinguishes it from rod-cone dystrophies such as retinitis pigmentosa, where ERG findings progressively deteriorate.
Swatches
Normal
HEX: — • RGB: — • xy: —
Oguchi affected
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ΔE (CIE76)
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ΔE (CIEDE2000)
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Deep preview
Normal
Oguchi (deep)
Chromaticity (CIE xy)
Rod pathway failure chromaticity shift
D65 white point: 0.313, 0.329
Image simulation

Oguchi disease simulation models the scotopic rod pathway deficit from arrestin (SAG) or rhodopsin kinase (GRK1) loss-of-function mutations. In the light-adapted state, photopic/cone vision is entirely normal — the simulation therefore models adaptation states where patients attempt to function in low-scotopic or mesopic luminance conditions: rods constitutively exhausted from phototransduction arrest cause absent rod ERG B-wave and complete clinical night blindness. The prolonged dark adaptation state models partial rod recovery after 2–12 hours of complete darkness — the minimum required for GRK1 or SAG pathway reset. The Mizuo-Nakamura phenomenon itself (the golden fundus sheen) is a funduscopic sign, not a direct measure of colour perception — the colour shift modelled here approximates the scotopic function loss, not the fundus sheen appearance per se. ΔE2000 per Sharma et al. (2005). Not for clinical diagnosis — Oguchi disease requires full-field ERG (scotopic and photopic), dark adaptation testing, and fundus examination. Any patient with congenital night blindness and a characteristic golden fundus sheen that clears after 2-12 hours in the dark should be referred for clinical electroretinography and genetic testing.

Multi-condition comparison
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Compare classic Oguchi (light-adapted, absent scotopic), prolonged dark adaptation recovery (Mizuo-Nakamura reversal phenomenon), and the advanced cone-involvement variant. Scotopic simulation applies rod pathway deficit model to uploaded images.