Eyes - optic neuritis
Eyes - optic neuritis
About the optic nerve
The optic nerve connects the
eye
to the
brain
. Our sight relies on the optic nerve transmitting information on shape, colour and pattern from the back of the eye (retina) to the brain’s visual centres. Optic neuritis is inflammation of the optic nerve that causes blurred, grey and dim vision. The symptoms can range from mild to severe, depending on the extent of the inflammation.
Optic neuritis can occur at any age, but people in their 30s are most commonly affected. Vision improves by itself in up to 80 per cent of cases, while some degree of reduced vision is permanent for the remaining 20 per cent. A number of diseases and conditions can trigger this inflammation, including multiple sclerosis. Optic neuritis is also known as retrobulbar neuritis.
The optic nerve and optic neuritis
The optic nerve is actually more than one million individual nerves bundled together. Each nerve plays a significant role in sending information from the retina to the brain. Inflammation causes affected nerves to swell, which means they cannot work properly.
The degree of visual impairment experienced with optic neuritis depends on how many nerve fibres are inflamed – the more nerve fibres affected, the worse the symptoms. Generally, eyesight deteriorates over a few days rather than suddenly. The peak of vision loss usually happens about a week after the symptoms first appear.
Symptoms of optic neuritis
Symptoms of optic neuritis can include:
blurred vision
grey vision (colours seem faded)
dim vision
pain in the back of the eye, especially during eye movement.
Symptoms may worsen if you are hot, for example, after playing sport or showering.
If you have these symptoms, contact your doctor immediately. Your doctor should send you to a hospital emergency department if they suspect you have optic neuritis.
In about 70 per cent of cases, only one eye is affected.
Causes of optic neuritis
Some of the many conditions and diseases that can cause optic neuritis include:
cytomegalovirus
hepatitis B
herpes
HIV
Lyme disease
measles
multiple sclerosis
mumps
paranasal sinus infection
radiation therapy
syphilis
tuberculosis
.
Optic neuritis and multiple sclerosis
Optic neuritis can be the first symptom of multiple sclerosis (MS), but this is only true for some people. Not everyone with optic neuritis will develop MS. There are many people who only have one attack of optic neuritis and do not develop any neurological problems.
An
MRI scan
can assess your risk of developing MS. If there are small spots on the brain scan, your risk of developing MS is higher. It is estimated that the risk of people who have optic neuritis developing MS within 10 years is 30 to 60 per cent, depending on whether these spots are seen on the MRI scan.
Optic nerve fibres are wrapped in myelin sheaths that help to conduct nervous system messages. With MS, the myelin sheaths become inflamed, causing plaques or lesions to appear.
Vision problems are a common first symptom of MS. However, optic neuritis doesn’t mean that developing MS is inevitable.
Other vision problems linked to MS
Apart from optic neuritis, other common vision problems associated with MS include:
nystagmus
– the eyes make involuntary ‘jumping’ movements, both horizontally and vertically
diplopia
– the person experiences double vision.
Diagnosis of optic neuritis
Optic neuritis can be mistaken for a number of other eye conditions such as ischaemic optic neuropathy, so careful diagnosis is important. Tests may include:
eye examination
colour vision tests
peripheral (side) vision tests
– to test visual field
MRI scan
– this scan is helpful to diagnose the condition and also to give information that will be able to assess the risk of the person developing MS.
Subclinical optic neuritis
A person may have demyelination of the optic nerve but not experience any visual symptoms. This is known as subclinical optic neuritis. The damage to the optic nerve can still be identified by certain tests, including electrical diagnostic tests and visual field examination.
Treatment for optic neuritis
Permanent damage to the optic nerve occurs in about 85 per cent of cases, but the damage does not always cause serious vision problems. In many cases, optic neuritis is short-lived and resolves by itself without treatment in around four to 12 weeks. The person’s vision improves once the inflammation subsides.
In severe or chronic cases, intravenous corticosteroids may be used to speed along recovery. However, the use of oral corticosteroid therapy is controversial. For example, some research suggests that it may increase the risk of recurrence. Regular eye examinations are important. The person should also undergo further tests to check for the presence of MS.
Where to get help
Your
GP (doctor)
Ophthalmologist
Neurologist
MS
Australia
External Link
Tel.
1800 042 138
The Royal Victorian Eye and Ear
Hospital
External Link
Tel.
(03) 9929 8666