Leber hereditary optic neuropathy (LHON)

Leber Hereditary Optic Neuropathy (LHON) is a rare genetic disorder that primarily affects the optic nerve, leading to significant vision loss. It is caused by mutations in the mitochondrial DNA, which are organelles within cells responsible for energy production. In a minority of cases, in addition to optic nerve damage, LHON can also involve the heart, muscles, and brain, though these systemic manifestations are less common.

The disease is maternally inherited, meaning only the mother can pass the affected gene to her children. However, not every individual who carries the genetic mutation will develop the disease. Males are at a higher risk of developing the symptoms of LHON compared to female carriers.

The hallmark symptom of LHON is a rapid, painless loss of central vision. Vision loss often begins in one eye, with the other eye affected weeks or months later; both eyes can also be affected at the same time. Peripheral vision is generally preserved, making complete blindness extremely rare.

The disease typically manifests between the ages of 15 and 35, but it can occur at any age. The vision loss is often permanent, though in some instances, partial recovery of vision may occur, depending on the specific genetic mutation causing the disease.

LHON is a hereditary condition, meaning the primary cause is the presence of a specific genetic mutation. However, certain lifestyle factors can influence the risk of disease onset or exacerbate its progression in carriers. These habits place metabolic stress on the mitochondria, which can accelerate the development of optic nerve damage.

Environmental risk factors include heavy smoking, excessive alcohol consumption, and an unhealthy diet. Carriers of the genetic mutation are advised to avoid these factors to potentially reduce the risk of disease onset or slow its progression.

Diagnosis of LHON is pursued when there is suspicion of the condition, such as unexplained vision loss or a family history of the disease. The diagnostic process involves a comprehensive eye examination and visual function assessment by an ophthalmologist, with particular attention to the optic nerve.

The crucial step in diagnosis is genetic testing. Currently, blood tests can identify the three main mutations responsible for approximately 90% of LHON cases. These tests are performed in genetic laboratories and provide definitive confirmation of the diagnosis. Genetic counseling is also recommended for family members of affected individuals to understand their own risk.

Oral idebenone, marketed as Raxone, is authorized in the European Union under exceptional circumstances for visual impairment from LHON in adults and adolescents aged 12 years and older. It can help some patients preserve or improve vision, but benefit is not guaranteed. Treatment should be started and supervised by a physician experienced in LHON. Availability and approval depend on the country, so discuss local options with your neuro ophthalmologist.

Gene therapies that aim to provide a functioning copy of an affected gene are also being studied. They are distinct from oral idebenone and their use depends on the mutation, clinical trials and local access arrangements. Low vision rehabilitation remains important alongside any medical treatment.

Since vision loss in LHON is often permanent, vision rehabilitation and low vision aids play a crucial role in helping patients maintain daily function and independence. These aids can include magnifiers, electronic magnification devices, adapted computer software, and other assistive technologies.

Additionally, psychological support and support groups can help patients and their families cope with the emotional and practical challenges of vision loss. It is important to discuss with the healthcare team available resources and strategies to improve quality of life.

Following a diagnosis of LHON, regular medical follow up with a neuro ophthalmologist is important. This follow up will include periodic vision tests and assessment of the optic nerve status. It is important to discuss lifestyle habits with your doctor, including avoiding smoking and excessive alcohol consumption, which may influence the disease course.

Seek medical attention promptly if there is a sudden decrease or significant worsening of vision, or if new non visual symptoms appear, such as muscle weakness or cardiac issues, especially if these have not been previously evaluated as part of the disease.