What is Leber’s hereditary optic neuropathy?
Leber’s hereditary optic neuropathy (LHON) affects the optic nerve. The optic nerve carries visual information from the eye to the brain.
LHON causes profound loss of central vision (sharpness and colour). It makes reading, driving and recognising faces difficult. We know that central vision is lost because of damage to the optic nerve cells at the back of the eye.
LHON vision loss is most common between the ages of 18-32 years. But some people lose vision in childhood or later in adulthood. It can happen to both men and women, but more men lose their sight.
How common is LHON?
LHON is a rare disease. It affects around 1 in 50,000 people worldwide.
What are the causes?
LHON is caused by genetic changes (mutations) in the DNA of the mitochondria – the powerpacks that provide energy to our cells. Mitochondrial DNA is only passed on from mothers.
Very few people with a LHON mutation will experience vision loss. At the moment it is hard to predict which family members will lose vision. Researchers at CERA are trying to understand why some people with the LHON genetic change lose vision, while others do not.
What are the signs and symptoms?
People with LHON have normal vision until the disease strikes. The first symptoms are usually blurred or cloudy vision when looking straight ahead. Vision loss is sudden and without pain.
Vision problems can start in one eye or both eyes at the same time. Most often, a person with LHON does not go completely blind. They will still have their peripheral or ‘side’ vision.
How is LHON diagnosed?
If you notice changes in your vision, see your eye healthcare provider.
They will do an eye exam to check your eye health and how well you can see. They will often ask about your general health and family history of eye problems.
You may need other tests to check how well the signal is getting from the eye to the brain. Sometimes an MRI (Magnetic Resonance Imaging) is required. This takes pictures that may help explain why vision is reduced.
If LHON is suspected, a specific test of blood or saliva may be needed. The sample is then sent to a laboratory for genetic testing to confirm if you have LHON.
Some people may know other family members with LHON. In other families it can occur without any previous history. The diagnosis can often be a shock.
Your doctor may recommend you visit a genetic eye clinic for genetic counselling. This may help you:
- understand and cope with your eye condition better
- talk about if children or family members are likely to be at risk of LHON
- if you are thinking of starting a family
- learn about any appropriate research studies or clinical trials.
At the genetic counselling appointment, some families ask about mitochondrial donation. This is a new assisted reproductive technology to help avoid people passing on mitochondrial conditions to their children. It is in limited use in the United Kingdom and other countries, but not yet legal in Australia. Mitochondrial donation is complex and researchers are looking at the safety and how well this technique works.
In Victoria, you can obtain genetic counselling through the Ocular Genetics Clinic at the Royal Victorian Eye and Ear Hospital. In other Australian states, you can be referred to your local clinical genetic service for genetic counselling.
What treatment is available?
There is currently no cure or treatment for LHON. Management focuses on helping people with their vision loss.
Mobility training, technology and visual aids can help people with LHON lead a relatively independent life. These includes screen readers, voice activated devices and software that magnifies text. You can get more information through Vision Australia and Guide Dogs Australia.
Scientists around the world are working on possible treatments. This includes gene therapy, stem cells and the effects of medications or supplements.
What are possible triggers for vision loss?
It is difficult to predict who may lose vision. But adopting a healthy lifestyle may reduce the risk. This includes:
- not smoking
- drinking alcohol in moderation
- eating lots of fresh fruits and vegetables
- wearing head protection in contact sports.
Some medications or recreational drugs also have the potential to trigger vision loss. If you’re at risk of LHON vision loss, check with your doctor or pharmacist before taking medications.
What LHON research is happening at CERA?
Dr Isabel Lopez Sanchez is a Principal Investigator at CERA. She’s researching the cellular and molecular changes that occur in LHON. She hopes her discoveries will lead to treatments to prevent or reverse the disease.
Dr Sanchez also works with Professor David Mackey and Lisa Kearns at CERA to provide an update on the number of people affected by LHON in Australia. Together they are also looking at other genetic and environmental factors that could protect or trigger vision loss.
Professor Alex Hewitt, Dr Sandy Hung, Lisa Kearns and Dr Helena Liang are researching genetic editing technology in the hope of developing new treatment options for LHON.
How can I help?
You can support LHON research at CERA by making a donation or participating in LHON research – please phone +61 3 9929 8360.