Sudden vision loss is when you lose some or all of your vision quickly. The loss can happen within a few minutes or over a few days. Vision loss differs from blurry vision. Blurry vision is when you don't see as clearly as you once did.
Sudden vision loss is an emergency—go to the hospital right away.
Most common causes:
A blocked blood vessel in your eye
An eye injury
Bleeding inside your eye—people with diabetes are at risk for this
Less common causes:
Some problems cause total vision loss. The same problems may cause only partial vision loss if they affect only part of your eye.
Go to the hospital right away if you have sudden vision loss. Most of the time, the cause is serious.
Even if your vision returns quickly on its own, sudden vision loss can be a sign that you may have had a mini-stroke.
Doctors will ask about your symptoms and health history.
Check your vision with an eye chart
Check how your eyes react to light
See whether your eyes can follow a moving object
Put some liquid drops in your eye (you may have a burning feeling that lasts a few seconds)
Look into your eye using a special magnifying light (the light is very bright)
Measure the pressure in your eye (there are many ways to do this, but none of them hurt)
Check whether you can see colors
They may also check other parts of your body, such as your skin or nervous system.