What is Leber's hereditary optic neuropathy (LHON)?
Leber's Hereditary Optic Neuropathy (LHON) is an inherited form of vision loss, characterised by rapid, painless vision loss in both eyes. It usually occurs in a person’s teens or twenties, but in rare cases, it may appear in early childhood or later in adulthood. For reasons yet unknown, it is much more common in males than females.
There is no current treatment for LHON, therefore research into preventative treatments is of paramount importance.
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Causes of LHON
LHON is one of the most common types of mitochondrial optic neuropathies, an important group of disorders that affect at least 1 in 10,000 individuals in the UK. One of the other common disorders in this group is called Autosomal-Dominant Optic Atrophy (ADOA).
These diseases are characterised by the malfunction of mitochondria, small organelles present in our cells. Mitochondria convert the food we eat into energy, playing a key role in cell function. In LHON, mutations in our genes lead to a harmful change in the mitochondria, which lose their normal function. The mutations particularly affect cells in the optic nerve that relay visual information to our brain, and this leads to progressive blindness.
Symptoms of LHON
Vision loss is typically the only symptom of LHON. Early symptoms include blurring and clouding of vision, either in just one eye or in both eyes at the same time. If only one eye is affected at first, symptoms in the other eye typically occur within a few weeks or months. Central vision, required for reading, driving and focussed tasks, worsens over time, with severe loss of sharpness and colour vision. Peripheral vision, however, remains intact, so people affected can usually walk around unaided.
If you notice problems with your vision, and any of the symptoms above, make an appointment with your optician or your GP who may refer you to a specialist, if necessary.
Your optician will perform a variety of tests on your eyes to detect the cause of vision loss. Because it is a very rare disease, LHON can often be mis-diagnosed as another condition. Only through a blood test, where the gene mutation can be identified, can the disease diagnosis be confirmed. If you are diagnosed with LHON, your optician will refer you to a consultant ophthalmologist who is a specialist in LHON.
Treatment for LHON
There is currently no cure for LHON and treatment options to slow the progress of the disease are limited. Genetic counselling, which is usually recommended for inherited conditions, can be difficult in the case of LHON because genetic testing cannot predict age of onset, severity, or rate of progression in carriers of the gene mutation.