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night blindness, a visual disorder manifested by partial or total inability to see objects in the twilight or at night.

Nyctalopia may arise in connection with certain organic diseases of the retina, choroid coat, or optic nerve, or with glaucoma (symptomatic nyctalopia); in connection with poor general nutrition due to starvation, certain liver diseases, malaria, alcoholism, or other conditions accompanied by a deficiency or total absence of vitamin A (functional nyctalopia); or in connection with congenital pigment degeneration of the retina (congenital nyctalopia). The immediate cause of nyctalopia is connected with structural changes in the retinal rods or a deficiency of rhodopsin (visual purple), which disintegrates in the light but is restored in the dark in the presence of vitamin A. Nyctalopia patients suffer from photophobia in bright light and sharply reduced vision in the twilight and at night. They may also suffer from reduced color sensitivity with respect to blue and yellow. Sometimes their visual field is narrowed and its acuity diminished. Nyctalopia is usually exacerbated in early spring because of insufficient vitamin A in the food.

A fully balanced diet, cod liver oil, and intake of vitamins A, B1, B2, and C are important to both treatment and prevention. In cases of symptomatic nyctalopia the causative disease should be treated.


Katsnel’son, A. B. Vitaminy i avitaminozy v oftal’mologii.[Cheliabinsk] 1947.


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Clinically, this family experienced nyctalopia at start of 2nd decade of age among all affected individuals with uniform pattern which masked the complete vision in progressive age.
The age at onset of nyctalopia and rate of progression of vision loss varied widely.
Affected individuals first experience defective dark adaptation or nyctalopia (night blindness), followed by reduction of the peripheral visual field (known as tunnel vision) and, sometimes, loss of central vision late in the course of the disease.
Vitamin A deficiency is a global issue and can result a number of health issues, including reversible night blindness, or nyctalopia.
Wagner syndrome may further be differentiated from Snowflake degeneration by its alternative genetic mutation (in CSPG2), more pronounced chorioretinal atrophy, nyctalopia, pseudoexotropia from the congenital temporal displacement of the fovea, and poorer end visual outcome.