LHON, or Leber hereditary optic neuropathy, is a disease that can be responsible for a major loss of central vision in some individuals. In this article we will take a look at some basic information for this condition.
What is LHON?
Leber hereditary optic neuropathy is a rare hereditary condition caused by mutations in the mitochondrial genome. Those mutations can lead to the death of cells in the optic nerve, which would impair the vision of the individual.
It can only be inherited from the mother, since its only egg cells that contribute mitochondria to the embryo. Fathers can't pass it down even if they have LHON themselves or are carriers of the genes that cause it.
Who Is at Risk of Having LHON?
Since LHON is a hereditary condition that can only be inherited from the mother, everyone who has a female family member that either has LHON or is a carrier of the gene that causes it is at risk of developing it. Being a carrier doesn't mean that you'll develop LHON, and only around 50% of men and 10% of women that carry the mutated gene suffer vision loss.
Some factors that could increase the risk of developing LHON are:
- Gender. It's not clear why, but LHON is much more likely to occur in men. Some evidence suggests that men might be more susceptible to mitochondrial defects.
- Age. LHON appears mostly in young adults. While the age of onset is mostly between 20 and 30, it can still appear at any age.
- Smoking and drinking alcohol can also trigger LHON.
What Are the Symptoms of LHON?
LHON is painless and it's usually diagnosed when people get a medical exam after noticing changes in their vision or if they're aware that they could be at risk. LHON can cause:
- Sudden blurring or clouding of vision.
- Reduced colour perception.
- Loss of central vision.
Symptoms can appear in either one or both eyes. In almost all cases, even if only one eye was affected initially, LHON also appears in the other eye within months.
This condition mainly affects the central vision, while the peripheral vision remains mostly intact. In some cases vision can slightly improve over time after the initial loss of sight, but that mainly depends on the type of mutation that caused LHON.
In the most common type of mutation, vision loss is severe and the recovery is minimal. There is a second type of mutation that doesn't cause a significant loss of vision and in which individuals can usually recover most of it. In the third common case, the loss of vision is moderate, but it keeps worsening over time. Those 3 mutations amount to about 9/10 of all LHON cases. Remaining cases are caused by very rare mutations.
Is There a Treatment or a Cure for LHON?
Right now there is no cure for LHON. While there are a few methods that can give fair results, there is no defined treatment for this condition. Some mitochondrial supplements and Idebenone may prove beneficial. Other methods, such as gene therapy, are being actively researched.
Visual aids can help you perform tasks as usual. There are also different services available to help you adjust to your new lifestyle.
Living with LHON can be very challenging, but you will still be able to lead a fulfilling life with the right support and tools. As with many conditions, prevention and an early diagnosis can be essential in protecting your vision. Make sure to have regular eye examinations and book an appointment with your ophthalmologist if you think you're at risk of developing LHON.