Various conditions causing poor night vision, sometimes called night blindness, have been known for centuries. Many disorders of the retina cause night blindness and most of these are progressive and associated with other ocular disease. However, several conditions causing difficulties with night vision are not progressive nor are they part of other syndromes. These are generally referred to as congenital stationary night blindness (CSNB).
Difficulty seeing at night is the primary symptom of congenital stationary night blindness. The condition is present at birth and no progression occurs. Daytime vision may be reduced to some degree as well. Mild color vision defects can sometimes be detected.
In this disease (CSNB2A) nearsightedness is common and 'dancing eyes' can be present. Males with this form usually have vision in the range of 20/30 to 20/200. Some individuals have crossed eyes as well.
At least 8 different mutant genes are known to cause CSNB. This type (CSNB2A) is caused by a mutant gene on the X-chromosome and therefore virtually always affects only males. Mothers who carry the mutation do not have night blindness but can pass the mutation to half their sons who will have night vision problems. Half of her daughters will likely be carriers.
Diagnosis is based on an ophthalmological examination. An electroretinogram (ERG) test is important to establish the diagnosis and to rule out other retinal disease. This is a stationary disease without significant progression and no systemic disease is present.
Many individuals with this type of congenital night blindness are nearsighted and require glasses or contact lenses for better vision.