New research has revealed for the first time the number of Australian families affected by genetic mutations that cause Leber hereditary optic neuropathy (LHON), a genetic eye disease so rare that some ophthalmologists may have never encountered a case.
The study, which reveals that 96 Australian families are affected by the genes, presents the most up-to-date statistics of the disease in the world.
It also reveals the risk of losing vision from the disease may be less than previously reported.
The research, led by Professor David Mackey from the Lions Eye Institute and University of Western Australia and Dr Isabel Lopez Sanchez from the Centre for Eye Research Australia (CERA) and University of Melbourne, is published in the American Journal of Human Genetics.
Caused by changes in the DNA of the mitochondria, LHON affects the optic nerve, but it carries an uncertain diagnosis as even though family members may have the same genetic mutation their vision will not be impacted in the same way.
Very few people with a LHON mutation will experience vision loss. However, some may experience sudden and permanent vision loss – with blindness sometimes occurring in a matter of weeks.
For 30 years, Mackey has worked with eye specialists around the country and the research team at CERA to be able to assemble some of the most accurate data about LHON risk anywhere in the world.
“People affected by LHON never go completely blind, and a small percentage may recover some vision, but the vast majority will not be able to drive, read or recognise faces,’’ he said.
“Although we are still working to find treatments for LHON, knowing exactly the risk for vision loss allows us to design better clinical trials.
“If the Federal Government passes legislation to allow mitochondrial donation, we will be able to give family members accurate risk data so they can make an informed decision about opting for this new treatment.”
The new study found 355 people are currently living with vision loss because of it.
It also shows the overall risk of losing vision if you have the LHON gene is 17.5% for males (one in six males) and 5.4% for females (one in 20 females). This is significantly less than the popularly quoted risk of 50% for males (one in two males) and 10% for females (one in 10 females).
Ms Lisa Kearns, a research genetic counsellor and orthoptist at CERA has worked with LHON families for 20 years, says LHON has traditionally been known as a young man’s disease.
“However, the study’s findings confirm LHON can also affect a smaller number of women, older adults and younger children,’’ she said.
The new information is expected to help families affected by LHON make better informed family planning decisions.
It will also aid studies researching why some people are at higher risk of vision loss from the disease and help identify patients suitable for future clinical trials into potential cures.
CERA principal investigator Dr Isabel Lopez Sanchez said because LHON is very rare, some ophthalmologists may have never encountered a patient with the disease.
“As a result of our study we want them to consider LHON could be a possibility if a woman, younger child or older adult has lost their vision, to avoid a delayed diagnosis or even misdiagnosis,” she said.
Lopez Sanchez said the study will provide researchers with a comprehensive database of people they can ask to take part in future clinical trials and studies aiming to prevent or treat vision loss.
“It will also help us design accurate trials and studies, which is very important, as that will help us develop efficient treatments,” she said.
Case study
Duncan Meerding was 18 when he realised he had a major problem with his vision when he couldn’t see the TV screen.
“I was moving my hands about for perspective and I noticed there was a giant blind spot in my left eye. I was like, ‘Ah, I could just be overtired’,” recalls Meerding, who is now an award-winning furniture and lighting designer in his 30s.
But it wasn’t a simple matter of fatigue. After visits to doctors and eye specialists, Meerding was diagnosed with LHON. Within eight months, he also lost central vision in his other eye.
He recalls losing his vision was, initially, “psychologically and physically difficult to deal with”.
“Luckily, I had great support from doctors and my Uncle Doug, who also has vision loss from LHON. Because of that support, I came to realise having LHON wasn’t the end of the world – it was the beginning of something new,” he said.
While welcoming the new study’s findings, Meerding encourages anyone with LHON or a similar condition to carve out a life in the here and now.
“Live your life as someone with vision loss; don’t put off your life,” he said. “If and when treatment comes along, that will be great but, in the meantime, learn how to adapt.”
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