| Oguchi disease | |
|---|---|
| Other names | Congenital stationary night blindness, Oguchi type 1 or Oguchi disease 1 [1] |
 | |
| Oguchi disease has an autosomal recessive pattern of inheritance. | |
| Specialty | Neurology  |
Oguchi disease is an autosomal recessive [2] form of congenital stationary night blindness associated with fundus discoloration and abnormally slow dark adaptation.
Several mutations have been implicated as a cause of Oguchi disease. These include mutations in the arrestin gene or the rhodopsin kinase gene. [1]
| Type | OMIM | Gene |
|---|---|---|
| Type 1 | 258100 | SAG |
| Type 2 | 613411 | GRK1 |
The condition is more frequent in individuals of Japanese ethnicity. [3]
Oguchi disease present with nonprogressive night blindness since young childhood or birth with normal day vision, but they frequently claim improvement of light sensitivities when they remain for some time in a darkened environment.[ citation needed ]
On examination patients have normal visual fields but the fundi have a diffuse or patchy, silver-gray or golden-yellow metallic sheen and the retinal vessels stand out in relief against the background.[ citation needed ]
A prolonged dark adaptation of three hours or more, leads to disappearance of this unusual discoloration and the appearance of a normal reddish appearance. This is known as the Mizuo-Nakamura phenomena and is thought to be caused by the overstimulation of rod cells. [4]
Other conditions with similar appearing fundi include[ citation needed ]
These conditions do not show the Mizuo-Nakamura phenomenon.
Oguchi's disease is unique in its electroretinographic responses in the light- and dark-adapted conditions. The A- and b-waves on single flash electroretinograms (ERG) are decreased or absent under lighted conditions but increase after prolonged dark adaptation. There are nearly undetectable rod b waves in the scotopic 0.01 ERG and nearly negative scotopic 3.0 ERGs.[ citation needed ]
Dark-adaptation studies have shown that highly elevated rod thresholds decrease several hours later and eventually result in a recovery to the normal or nearly normal level.
The S, M and L cone systems are normal.
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It was described by Chuta Oguchi (1875–1945), a Japanese ophthalmologist, in 1907. The characteristic fundal appearances were described by Mizuo in 1913.Treatment of the disease is limited. In the People's Republic of China, high doses of Vitamin K and zinc are infused but thus treatment has been declared as quackery in the Republic of China (Taiwan) and by the Timor Leste Academy of Ophthalmology. In the U.S., afflicted persons have taken high doses of zinc (240 mg every two hours).
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Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors, inner retinal cells, and the ganglion cells. Electrodes are placed on the surface of the cornea or on the skin beneath the eye to measure retinal responses. Retinal pigment epithelium (RPE) responses are measured with an EOG test with skin-contact electrodes placed near the canthi. During a recording, the patient's eyes are exposed to standardized stimuli and the resulting signal is displayed showing the time course of the signal's amplitude (voltage). Signals are very small, and typically are measured in microvolts or nanovolts. The ERG is composed of electrical potentials contributed by different cell types within the retina, and the stimulus conditions can elicit stronger response from certain components.
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Rhodopsin kinase is a serine/threonine-specific protein kinase involved in phototransduction. This enzyme catalyses the following chemical reaction:
Glutamate receptor, metabotropic 6, also known as GRM6 or mGluR6, is a protein which in humans is encoded by the GRM6 gene.
S-arrestin is a protein that in humans is encoded by the SAG gene.
The mission of the Foundation Fighting Blindness is to fund research that will lead to the prevention, treatment and cures for the entire spectrum of retinal degenerative diseases, including retinitis pigmentosa, macular degeneration, Usher syndrome, Stargardt disease and related conditions. These diseases, which affect more than 10 million Americans and millions more throughout the world, often lead to severe vision loss or complete blindness.
The Mizuo–Nakamura Phenomenon is a phenomenon observed in Oguchi's disease. It was named after Gentaro Mizuo (1876–1913) and Bunpei Nakamura (1886–1969), Japanese ophthalmologists.
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