The first and main symptom of LHON is usually a sudden, painless blurring and clouding of your central vision. This typically happens in just one eye at first. This is known as the acute phase of LHON.
During the acute phase of LHON, a similar type of vision loss tends to develop in the second eye. In some cases, the vision loss can happen in both eyes at the same time. However, it usually happens in the following weeks and months. Almost all people with LHON experience central vision loss in the second eye within 1 year.
There have been cases where vision loss has improved over time, however, it is much more common for the loss to be permanent.
What is central vision loss?
The type of vision loss in LHON is usually central vision loss.
This means the middle part of what you can see out of the eye becomes lost or
blurred. But the area around the edge of what you can see (known as peripheral
vision) is still there.
Central vision is needed for detailed tasks such as reading, driving, and recognising faces. However, as long as the peripheral vision is not lost, people can often still walk around independently.
Other visual symptoms
LHON can also affect your colour vision, making it harder to tell different colours apart. The sharpness (known as visual acuity) of the remaining vision can also get worse over time.
It is important to note that the extent of the vision loss and other symptoms can be very different between different people.