What is NAION?
What we see of the world is focused onto the back of our eyes onto the lining at the back of our eye (the retina). The retina converts the image into electrical impulses which travel through the optic nerve (the nerve of sight) to the brain.
The optic nerve is supplied by very small blood vessels, and it is the blood flow in these blood vessels that is affected in NAION. The blood supply to part of optic nerve is reduced, resulting in damage to the nerve fibres and this causes the loss of some of the sight in the eye.What causes NAION?
Despite many theories and suggestions, the exact cause of NAION is not known. However, some conditions can increase the risk of this happening, such as a raised cholesterol or diabetes.
Initially the blood supply to the optic nerve may be lower than normal, but the final event may be an overnight drop in oxygen levels or blood pressure. This reduces the blood supply further and causes damage and swelling of the optic nerve.
What happens early in NAION?
The commonest situation is to wake up one morning and feel as if there is something covering part of the vision in the eye. This commonly happens in the lower part of the vision towards the side of the nose. In some patients the central part of the vision is abnormal, while in others the upper or lower half of the centre vision is affected. In the first few weeks this area may become greyer and more obvious. Most people find that some or all of the lower half of the vision is affected in one eye. The whole process is usually painless.
It is common in the first weeks to see flashes of light in the affected area when the eyes are closed. This gradually becomes less and then stops happening.
Will the eyesight change later?
The affected area of vision may become more obvious in the first month or two but it is very unusual for the damage to spread to new areas of vision in the same eye during this time.
Unfortunately the optic nerve damage that has taken place does not recover. However, the optic nerve and retina are swollen in the first weeks and as the swelling disappears some modest improvement can occur in the less badly affected area of vision in that eye.
Will the other eye become affected?
There is a low risk of the other eye being affected in the same way- this happens in about 15-20% (1 in 7 to 1 in 5). The risk seems to lessen as time goes by, and it is unusual for a second eye to become affected more than 18 months after the first eye episode.
The risk can be kept to a minimum by ensuring that risk factors such as a raised cholesterol are treated. People with NAION are not more likely than others to die from stroke or heart disease.
Is there any treatment?
There is no single treatment that has been proven to prevent NAION or to reduce the amount of visual loss. However, there are some steps that may reduce the risk of NAION occurring in the other eye.
Reducing cholesterol: if the levels are raised then drugs such as statins can be given to reduce those levels. Your GP would prescribe this for you.
Treating high blood pressure: while this is important, it needs to be done slowly to avoid dropping the blood pressure too low (especially at night). Some advise taking blood pressure medication in the morning to avoid this problem.
Treating other conditions: any condition that can affect small blood vessels (such as diabetes) needs to be kept controlled. Your usual consultant will advise you.
Aspirin: this keeps the blood flowing and is commonly used to reduce the risk of NAION occurring in the other eye. The dose is low, often 75mg once daily. Your consultant of GP can advise you if it is safe to take this.
Glasses: new or replacement glasses will not restore the vision that has been damaged. However, if you had previously needed glasses, then wearing the glasses will make the damaged area much less noticeable. If you feel you need new glasses, wait until the swelling at the back of the eye has settled. This may take 1-2 months and your ophthalmologist will advise when it is appropriate to visit an optician.
Omega-3 fish oils: some have suggested using these in NAION because they help to keep small blood vessels healthy. They come in the form of concentrated fish oil capsules or liquid and are available in most chemists.
Antioxidants: these may help to reduce the risk of blood vessel damage and heart disease, but there is no evidence as yet that they reduce the risk of NAION in the other eye. There are many sources of antioxidants including vegetables, vitamin supplements and green tea.
Diet and exercise: a healthy diet and some exercise is always sensible. The exercise can be simply walking or swimming, which are as good as jogging or going to the gym.
Will I adjust to the loss of vision?
Yes. Because only one eye is affected, the normal eye starts to ‘fill in the gap’. The upper half of the vision will be normal in the affected eye, and for those whose central vision is unaffected they will find they can use the affected eye well. In time, most patients learn to ignore the damaged area of vision.
From the leaflet by Claud Regnard and Margaret Dayan
Newcastle upon Tyne, UK
My NAION Experience
An excellent and very informative page by Dr. Karl L. Wuensch,
with many, many helpful links is here.
Karl Wuensch's excellent summary of Hayreh, S. S.
(2009). Ischemic optic neuropathy, Progress in Retinal and Eye
Research, 28, 34 - 62.can
be found here
NAION Group at Yahoo
(a support group for those with Nonarteritic Anterior Ischemic Optic Neuropathy