The optic nerve connects the eye to the brain and carries visual signals from the retina that enables us to see. Consequently, any disease that damages this nerve can result in vision loss. A number of gene mutations lead to defects of such nerve conduction which may begin with damage to the nerve cells of the retina. This is the only type of optic atrophy that is caused by a mutation on the X-chromosome.
Only males have clinical disease. The first visual symptoms appear in childhood and loss of vision progresses slowly. Vision ranges from near normal to legal blindness. Most have some degree of color blindness. All affected males have evidence of damage to the optic nerve and some have other neurologic signs such as tremor, slurred speech, and unsteadiness but these are usually mild symptoms. Mental retardation has been noted in a few patients. Females who carry the mutation do not have any visual problems or evidence of neurologic disease.
This is an X-linked recessive disorder caused by a mutation on the X-chromosome. Only males are affected since their single mutated X-chromosome has no counterpart that makes a normal gene product. Their mothers carry the mutation on one of their X-chromosomes but are clinically normal since the other non-mutated X-chromosome presumably is able to cover for the single mutation. Such mothers, however, can expect that half their sons will be affected and half their daughters will inherit the mutant X-chromosome and become carriers like their mother.
The diagnosis is usually made by an ophthalmologist or sometimes by a neurologist. The prognosis is highly variable but once the optic nerve is damaged, the vision loss is not reversible. No treatment is available for the optic nerve damage but low vision aids can be helpful for everyday tasks.