Sudden vision loss in one eye Te kāpōtanga ki te karu kotahi

There are 3 main causes of sudden vision loss.

A blocked blood vessel

A common cause is a blood clot or a piece of plaque blocking an artery in your eye. Plaque is a hard substance that forms when fat, cholesterol and other substances build up in the walls of arteries.

This is called a transient ischaemic attack. A transient ischaemic attack of the eye has a special name, amaurosis fugax. It is usually painless but it is serious as it means you are at more risk of having a stroke.

Transient ischaemic attacks

Stroke

Giant cell arteritis

If you are aged over 50 and are also having headaches or scalp or jaw pain, for example, when you are chewing food, this could be because of giant cell arteritis. This is an inflammatory problem that affects blood vessels.

Giant cell arteritis

Migraine

Your vision loss is probably caused by a migraine if:

• you have a history of migraines
• you see sparkling lights or patterns as you lose your vision
• your vision recovers completely.

Migraines

When you have sudden loss of vision in one eye you may experience:

• complete or partial loss of vision
• a feeling like a dark shadow is covering all or part of your vision
• blurred or dim vision 
• flashes of light, or dots or lines in your vision
• light sensitivity
• pain around the eye (depending on the cause)
• redness of the eye (if there is an infection). 

To diagnose what is causing your vision loss, your healthcare provider or optometrist will ask about your symptoms and medical history. They will examine your eye and may refer you for further tests.

Seek immediate medical treatment to determine the cause of the vision loss. Accessing medical care may rule out life threatening conditions or prevent permanent vision loss.

The type of treatment you need will depend on the cause of the vision loss.