What is it?
Oguchi disease is a rare autosomal recessive retinopathy caused by mutations in the SAG gene (located on chromosome 2q37) that codes arrestin (Oguchi type 1), or mutations in the GRK1 gene (located on chromosome 13q34) that codes rhodopsin kinase (Oguchi type 2).
It is characterized by constant night blindness and the Mizuo-Nakamura phenomenon. Patients suffer from persistent night blindness from early childhood with normal daytime vision, although sensitivity to light often improves when they remain in the dark for extended periods.
The Mizuo-Nakamura phenomenon is the only symptom present in fundus examination and consists of an isolated morphological and functional retinal abnormality characterized by yellow-gold or silvery-grey discoloration of the fundus in the presence of light. A prolonged adaptation to darkness, lasting three or more hours, is sufficient to eliminate the background changes associated with the Mizuo-Nakamura phenomenon, which reappears with light.
How is it diagnosed?
The diagnosis is clinical and is based on the presence of night blindness and on the identification of the Mizuo-Nakamura phenomenon by biomicroscopic examination of the fundus and ERG, which shows a normal response of the cones, while the response of rods after several minutes of adaptation to darkness changes greatly. The change may regress once the Mizuo-Nakamura phenomenon is established.
How is it treated?
There is currently no specific treatment for Oguchi disease.
Visual prognosis is favorable in the absence of progression of symptoms, although Oguchi disease is considered a permanent condition, it can cause decreased visual acuity or narrowing of the visual field, especially in elderly patients.
Where do we treat it?
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