Optic neuritis: symptoms, treatment, recovery and the link with MS

RNIB lists the effects of optic neuritis in some detail. Vision becomes blurred, dim or faded over a few days, and may keep worsening for about two weeks. It is usually one eye, commonly affecting the central vision used for reading, screens and recognising faces, although side vision can also be involved. Both eyes can be affected in some types.

• A fuzzy patch or blind spot in the centre of vision.

• Colours, especially reds, looking washed out, and reduced contrast sensitivity.

• Difficulty judging distances and depth because one eye sees less well, which can make stairs, kerbs and pouring liquids harder.

• Flashing or flickering lights in some people.

• Pain or discomfort around the eye, usually worse with large eye movements, typically lasting a few days. RNIB says pain bad enough to stop you sleeping should be mentioned to a GP or eye specialist, as there may be another cause.

• Vision that worsens temporarily with heat, for example after a hot bath, exercise or a hot drink (RNIB).

RNIB cites a large 1992 trial of about 400 people which found that even without treatment more than 9 out of 10 people's vision improved within the first month after vision loss began. For the common demyelinating type, high-dose steroids can help vision recover faster and may protect the nerve, but studies show they do not change how well vision recovers in the long term, so benefit has to be weighed against side effects. The MS Trust agrees that over the long term there is no difference in recovery between people who take steroids and those who do not.

RNIB says steroids are more likely to be used when the optic neuritis is a rarer type such as MOGAD, CRION or NMOSD, when the other eye has very poor vision, or when symptoms are severe or interfere with important tasks such as driving for work. In those types early steroid treatment, ideally within 48 hours, can improve recovery. Steroids can be given through a vein in hospital for 3 to 5 days or as tablets for about 3 days, and sometimes a longer tapering course is needed.

• Pain relief: over-the-counter painkillers are often enough (RNIB).

• Immunosuppressant medicines may be needed for rarer types such as MOGAD, CRION and NMOSD, sometimes long term.

• If infection is the cause, antimicrobial or antifungal medicines are used, and RNIB warns that steroids can be harmful in infectious optic neuritis.

RNIB says some cases are autoimmune, meaning the immune system mistakenly attacks healthy tissue. Associated autoimmune conditions include multiple sclerosis, neuromyelitis optica spectrum disease (NMOSD), myelin oligodendrocyte glycoprotein antibody disease (MOGAD) and chronic relapsing inflammatory optic neuritis (CRION). Less often it follows an infection or a reaction to infection or vaccination.

The MS link is the reason for the investigations. The MS Trust says that for 1 in 4 people with MS, optic neuritis was the first symptom they noticed, and that seven out of ten people with MS will have optic neuritis at some point. RNIB gives the other side of the coin: about 62 in 100 people with a first episode of demyelinating optic neuritis do not go on to develop MS within 10 years. Only a neurologist can diagnose MS, after further tests.

Optic neuritis is also associated with a rare condition called neuromyelitis optica, and the MS Trust points out that its treatments differ from those for MS, so a doctor needs to confirm exactly what is happening.

The optic nerve is the cable between the back of the eye and the brain. In optic neuritis it becomes inflamed, often because the insulating myelin coating around its fibres is attacked and breaks down, which slows or blocks the signal. RNIB describes this "demyelinating" form as the commonest type, and in most people no cause is found, which is called idiopathic.

The MS Trust calls it a common eye problem that is a condition in its own right but is also strongly associated with multiple sclerosis. It puts the frequency in the general population at between one and five people in 1,000. The reassuring part, highlighted by RNIB, is that it usually affects vision in the short term and for most people gets better without causing major lasting loss.

Optic neuritis is assessed by looking at the eye and the vision, and because of the MS connection it often involves more than an eye examination. RNIB says an eye examination or an OCT scan can show lasting damage to the optic nerve, called optic atrophy, in some people, and that your ophthalmologist can explain whether your episode could be linked to MS.

The MS Trust says that, given the connection with MS, people with optic neuritis are likely to be asked to have a range of tests, which could include blood tests, an MRI scan and visual evoked potential tests, to see whether a doctor can diagnose MS. The NHS says there is no single test to diagnose MS, and that a neurologist will ask about symptoms and may arrange blood tests, an MRI scan, a lumbar puncture or tests with sensors that measure how quickly messages from the eyes travel to the brain. RNIB says only a neurologist can diagnose MS, after further tests.

Pain usually improves before vision does. RNIB says vision can keep improving for 6 to 12 months and has usually recovered as much as it will by about a year, with most people with the acute demyelinating type making an excellent long-term visual recovery. Some are left with faded colours, reduced contrast, less sharp vision or trouble judging depth or movement, and in rare cases recovery is limited.

Optic neuritis can come back, in either eye. For the common type RNIB reports that about 28 in 100 people had another episode within five years and about 35 in 100 within 10 years, which also means roughly 65 in 100 had none in 10 years. Recurrence is more likely with the rarer types. Practical help, from low-vision aids to driving advice, is available if lasting changes occur.

The MS Trust says a very sudden loss or change of vision could be serious and needs prompt medical attention. It also says the symptoms can be due to other eye conditions or headaches, which is a reason for a proper assessment rather than waiting to see.

The NHS multiple sclerosis page says to call 999 or go to A&E if you have sudden loss or blurring of vision, sudden weakness or numbness in one arm, or problems with balance and co-ordination, because these could be signs of a stroke and need urgent medical attention. RNIB says the pain is not usually so great that it stops you sleeping, and that if it is worse than this you should let your GP or eye specialist know as there may be another cause.