Optic neuritis

The effect that optic neuritis can have on your sight varies. It can range from blurred vision to a complete loss of sight. It often affects just one eye, although it can affect both, either at the same time or one after another.

Some people notice a blurring or blind spot in the centre of their vision. Colour vision is usually affected – colours might appear darker or washed out. Some people have flashes of light, called phosphenes, when they move their eyes.

In some cases optic neuritis can be painful, particularly when you move your eyes. The pain usually lasts for a few days, and shouldn’t be severe enough to affect your sleep. If it does, there may be something else causing it.

Your eyesight tends to get worse over a few days to a week. For some people it can come on much quicker – in a few hours or overnight.

Optic neuritis is diagnosed by an ophthalmologist or neurologist. In order to reach a diagnosis, they will want to know how your vision is affected, when your symptoms came on, and whether you’ve had any previous neurological symptoms.

They may carry out some tests. These many include blood tests and ‘visual evoked potentials’. This tests how well your optic nerve is working, by checking how long it takes your brain to react to a visual signal. They may also carry out an MRI scan of the optic nerve, to look for signs of inflammation.

If this is your first MS-like symptom, you may also be referred to a neurologist for further tests, including an MRI scan of your brain.

> Read more about the tests for MS

Other eye conditions can look like optic neuritis, so, depending on your symptoms, you may need to have further tests. This is more likely if your symptoms aren’t typical, for example:

• if you have very severe pain that disturbs your sleep or limits how much you can move your eyes
• if you lose your sight completely in the affected eye
• if both of your eyes are affected
• if your sight hasn’t started to improve after three to four weeks

Optic neuritis will often improve on its own, usually within a few weeks, so you may not need any treatment.

However, if your symptoms are particularly severe – for example, if it’s affecting both eyes – or you want a faster recovery, you may be prescribed a course of steroids. These are given either as a tablet or as an infusion into your arm or hand (also called a 'drip'). Steroids have been shown to speed up recovery from optic neuritis, but they don’t make any difference to how your eyes will be when it's over.

Most people’s sight recovers well from optic neuritis.

The early stages of recovery can happen quite quickly, probably due to the inflammation of the optic nerve going down. Eight in ten people start to get better within three weeks, and nine in ten began to get better within five weeks.

A full recovery can take longer, and you may find that your sight continues to improve for up to a year after your first symptoms. About half of people with MS who get optic neuritis get it again within the next ten years.

Although your sight may recover to normal levels you may notice some subtle lasting changes to your vision. For example, you may find it harder to pick out colours, or distinguish between different colours. Things might not be as sharp as before. You might be less good at judging what you see at a distance.

You may also find that certain things like heat, exercise, fatigue or having a temperature make your vision worse. It'll get better when you cool down or are less tired. Your eyesight might vary during the day or from one day to the next.