Leber hereditary optic neuropathy (LHON) is an inherited form of vision loss. Although this condition usually begins in a person's teens or twenties, rare cases may appear in early childhood or later in adulthood. For unknown reasons, males are affected much more often than females.

Blurring and clouding of vision are usually the first symptoms of this disorder. These vision problems may begin in one eye or simultaneously in both eyes; if vision loss starts in one eye, the other eye is usually affected within several weeks or months. Over time, vision in both eyes worsens with a severe loss of sharpness (visual acuity) and color vision. This condition mainly affects central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. Vision loss results from the death of cells in the nerve that relays visual information from the eyes to the brain (the optic nerve). Although central vision gradually improves in a small percentage of cases, in most cases the vision loss is profound and permanent.

Painless vision loss is typically the only symptom of Leber hereditary optic neuropathy; however, some families with other signs and symptoms have been reported. These cases are described as "LHON plus." In addition to vision loss, the features of LHON plus can include movement disorders, tremors, and abnormalities of the electrical signals that control the heartbeat (cardiac conduction defects). Additionally, some people with Leber hereditary optic neuropathy develop features similar to multiple sclerosis. Multiple sclerosis is a chronic disorder that affects the brain and spinal cord (the central nervous system), causing muscle weakness, poor coordination, numbness, and a variety of other medical problems.

How common is Leber hereditary optic neuropathy?

The prevalence of Leber hereditary optic neuropathy in most populations is unknown. It affects 1 in 30,000 to 50,000 people in northeast England and Finland.