Ischemic optic neuropathy (ION), is a sudden loss of central vision and/or side vision because of poor blood flow to the optic nerve.  The optic nerve carries sight from the eye to the brain.

What are the symptoms of ION?

Sudden loss of central or side vision is the most common symptom.  You may notice loss of side vision in the lower half of reading vision.

Vision loss is usually at its worst when first noticed and in most eyes permanently remains at this level.  In a few eyes, vision either progressively worsens or improves over weeks or months.

ION could be considered a stroke of the optic nerve.  It generally does not cause any other symptoms, such as pain or double vision.  The risk of brain stroke is no greater for people with ION. 

People who have temporal arteritis, one cause of ION, may notice headaches and tenderness in the temple.  Joint aches and pains commonly affect the shoulders and hips of people with this blood vessel disorder.  They may also feel tired and run a fever, combined with recent weight loss.

How is ION diagnosed?

Your ophthalmologist will perform a complete eye examination, including pupil dilation.  Decreased blood flow usually results in swelling of the optic nerve, which your ophthalmologist can see when examining your eye.

A test of side vision (visual field), may also be performed.  Your ophthalmologist may recommend a check of blood pressure or a blood test for diabetes.  In addition, a blood test and/or biopsy of an artery in the temple to diagnose temporal arteritis may be required.

What causes ION?

The most common type of ION occurs in individuals over 40 years of age and is usually not related to other illness.  ION may be more common in people with diabetes or high blood pressure.

A less common type of ION occurring in people over 60 years of age is temporal arteritis.  This disease is an inflammation of certain arteries, including those in the eye.  Rarely, ION can occur after loss of large amounts of blood.

Can ION be treated?

ION has no proven treatment.  There is about a 25% risk that the other eye will develop ION.

There is no treatment to improve vision.  However, a study showed that 43% of patients will spontaneously experience some improvement of their vision over time.

Patients with ION caused by temporal arteritis have a very high chance of the other eye being affected unless treated with steroid tablets (cortisone).  The purpose of steroids is to prevent ION in the other eye, but this treatment rarely improves vision that is lost in the first eye.

What will happen to my vision?

Unfortunately, with either type of ION, vision loss is usually permanent.  For those with severe vision loss in both eyes, often some side vision is preserved. 

This side vision generally allows you enough sight to function at home independently.  Special visual devices are available which can help you to continue many daily activities.

Why are regular medical eye examinations important for everyone?

Eye disease can occur at any age.  Many eye diseases do not cause symptoms until the disease has done damage.  Since most blindness is preventable if diagnosed and treated early, regular medical examinations by an ophthalmologist are very important.

©1998 American Academy of Ophthalmology