Fundus albipunctatus is a rare autosomal recessive form of stationary night blindness characterized by the presence of white or white-yellow dots in the perimacular area and the periphery of the retina, with or without macular involvement. This disorder is inherited in an autosomal recessive manner and is most often caused by mutations in the RDH5 gene. This gene encodes the enzyme that is a part of the visual cycle, the 11-cis retinol dehydrogenase.
In patients with fundus albipunctatus, scattered yellow-white dots are seen in the posterior pole (sparing the macula) extending to the mid-periphery. These dots may disappear over time although they are typically stable. They are presumed to contain 11-cis retinal precursors (retinoids) and exist from the RPE/Bruch membrane complex to outer nuclear layer.
Optical coherence tomography can be helpful to evaluate fundus albipunctatus.In fundus albipunctatus, there are hyperreflective deposits in the RPE that extend up to the outer nuclear layer, corresponding to dots visualized on fundus examination. Fundus autofluorescence typically demonstrates a decreased background autofluoresence consistent with a dysfunctional retinoid cycle.
As can be seen on the dark adaptation curve, there is markedly delayed dark adaptation for both rods and cones. ERG findings follow the course of dark adaptation, resulting in a delay in reaching the full amplitude of the ERG, which parallels the delay in dark adaptation. When adequately adapted (which may take several hours and vary widely between patients), there are both normal psychophysical thresholds and normal ERG amplitudes. EOG likewise parallels ERG because a full EOG light rise will not be obtained until the patient with fundus albipunctatus has been dark-adapted for the period of time it takes to reach full dark adaptation.
Credit: Kemal Tekin, M.D., from Ulucanlar Eye Training and Research Hospital
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