Age and sex are important. This condition usually begins in people aged 15 to 35 years old and mainly affects male carriers. However, rare cases may appear in early childhood or later in adulthood.
Male carriers are at a much higher risk of developing symptoms than female carriers. The reason for this gender bias is still unclear.
LHON vision loss most commonly affects males when they’re aged 15 to 25. A young male has a lifetime risk of around 50% of developing the condition after a positive test result for a LHON mutation. This means they have a 1 in 2 chance of losing vision at some point in their life. This risk falls as years go by without experiencing symptoms. However, the risk never vanishes, as LHON symptoms can present late in life.
Females tend to be affected at an older age, often around times of oestrogen loss. There is a 10% chance of losing vision if you are a female carrier.