Leber Hereditary Optic Neuropathy (LHON)
Leber hereditary optic neuropathy (LHON) is a rare inherited condition that causes sudden or subacute loss of central vision.
Overview
Leber hereditary optic neuropathy (LHON) is a rare inherited condition that causes sudden or subacute loss of central vision. It affects the optic nerve, which carries visual information from the eye to the brain. Vision loss usually occurs in young adults, most commonly in males. The condition typically affects one eye first, followed by the second eye weeks or months later.
Causes and Genetics
LHON is caused by changes (mutations) in mitochondrial DNA. Mitochondria are structures inside cells that produce energy. Unlike most genetic conditions, LHON is inherited through the maternal line because mitochondrial DNA is passed from mother to child. Not everyone who carries a mutation will develop vision loss. Environmental factors such as smoking and heavy alcohol use may increase risk.
Symptoms and Features
Symptoms usually begin in adolescence or early adulthood but can occur at other ages.
Characteristic Symptoms and Features
- Sudden or painless blurring of central vision in one eye, followed by the other eye
- Difficulty reading
- Difficulty recognising faces
- Loss of colour vision
Other Associated Symptoms and Features
- Peripheral (side) vision is often preserved
- Some individuals may develop tremor, movement difficulties or heart rhythm abnormalities, although this is less common
Vision loss is often severe and permanent, though a small number of individuals may experience partial recovery.
Treatment
Low vision aids, occupational therapy and visual rehabilitation can help maintain independence. Avoidance of smoking and excessive alcohol is strongly recommended. Regular cardiac assessment may be advised in some individuals. Care is usually coordinated through specialist ophthalmology and genetics services.
Research and Future Directions
Ongoing research is focused on gene therapy approaches aimed at correcting mitochondrial DNA defects. Clinical trials are assessing treatments that improve energy production in optic nerve cells. Improved understanding of risk factors and earlier intervention may improve long-term outcomes.