Bright Sight

Oliver Backhouse, Consultant Eye Surgeon www.cataract.org.uk

Anterior Ischaemic Optic Neuropathy

1] What is Ischaemic Optic Neuropathy?

Ischaemic Optic Neuropathy (ION) is a sudden loss of central and / or side vision because of poor blood flow to the optic nerve (the information ‘wire’ from the eye to the brain). It is the most common cause of sudden decreased vision in patients older than 50 years. It is usually not related to other illness although may be more common in people with diabetes or high blood pressure. A less common type of ION is associated with a condition called temporal arteritis, which generally occurs in people over the age of 60 years. This disease is an inflammation of certain arteries, including those that supply the eye.

ION could be considered a small stroke in the optic nerve but unlike other strokes it is unassociated with weakness, numbness or loss of speech, nor is there any increased risk of a classic stroke later. There is no pain associated usually.

2] What causes ION?

It is not clear what causes the loss of blood supply to the optic nerve. These episodes may occur when there is a sudden drop in blood pressure (following an operation or with blood loss after an accident). Patients who smoke, or who have diabetes or high blood pressure, may be at a higher risk for ION. In young people, having a history of migraine or deep vein thrombosis might play a role in ION. People who are born with small / crowded optic nerves have a higher risk for developing ION.

3] What are the symptoms of ION?

Sudden loss of central or side vision (especially the lower half) is the most common symptom of ION. Vision loss is usually at its worst when first noticed, and in most eyes permanently remains at this level. Uncommonly, vision may worsen over time. ION generally does not cause other symptoms, such as pain or double vision. However, people with temporal arteritis may notice headaches and tenderness in the temple or pain when chewing, as well as fever and joint aches in their shoulders or hips. If these occur please bring them to the attention of the doctor.

4] How is ION diagnosed?

A medical eye exam is performed, including measuring your visual acuity, testing how your pupil reacts to light and examining the back of your eye. A visual field test may also be performed. It may be recommended to have your blood pressure checked and a blood test for diabetes. In certain cases a blood test can help assess the risk of temporal arteritis. Should the ION appear not typical, a brain scan may be ordered.

5] How is ION treated?

In people with central visual loss, up to 30% of patients may improve their central vision over time, though visual field problems are unlikely to recover. It has been suggested that Aspirin and vitamin supplements may decrease the chance of an episode in the opposite eye. It is rare for ION to recur in the same eye. It is important that your blood pressure be monitored by your general practitioner as high blood pressure or a sudden drop in blood pressure can cause worsening of vision in the effected eye or even ION symptoms in the other eye. People with ION should stop smoking.

FREQUENTLY ASKED QUESTIONS

What did I do to make this happen?

In most cases, there is nothing you or anyone else did to create this problem. The anatomy of your optic nerve is what you were born with. It is possible that smoking and high blood pressure may have increased your risk and, in rare cases, blood loss or a sudden drop in blood pressure can also contribute. Ultimately, we still do not understand the trigger that will produce the ischaemic event.

Will my vision get worse?

Within the first few days or weeks of the event, it is possible for there to be further worsening of vision. This, fortunately, is uncommon. To reduce this risk stop smoking and make sure that your blood pressure is adequately but not overly aggressively controlled. If your vision continues to worsen over more than a couple of weeks, be sure to contact your Ophthalmologist.

Will my vision get better?

In patients with central loss, there is a 30% chance of improvement although the visual field tends to remain the same. It is likely that there will be persistent problems seeing above or below or in certain areas around where you are looking. Experimental treatment with Avastin is showing some promise in helping vision recover.

How can I prevent involvement of the other eye?

Taking 75mg of Aspirin a day and vitamin supplements may reduce the chances. Avoiding cigarette smoke and proper treatment of elevated blood pressure may also help. Hopefully in the future, we will have better means of making it less likely to have second eye involvement.