Don’t Ignore Temporary Vision Loss        

We all have a slow loss of vision over the years, and require a simple change of glasses. The problem could be the onset of cataracts, glaucoma or macular degeneration. But the sudden loss of vision for only a few seconds may be an early sign of a transient ischemic stroke (TIA) or a mini-stroke.

If you suddenly can’t see, this is a medical emergency as it may be due to a blockage of the carotid arteries that supply blood to the brain. By early diagnosis of the cause and prompt treatment a major stroke, or what’s often called a “brain attack”, can be prevented. 
  

Gifford-Jones