Is it bad to have double vision?

Needs evaluation: If you have the onset of doubling recently it can be a symptoms of tumor, aneurysm, trauma or a stroke. Double vision is uncomfortable, usually intolerable as the images both are legitimate and your brain cannot choose between them. You should be seen by a neuro-ophthalmologist who can diagnose the cause.

Double vision causes: One way to test yourself: cover either eye with your hand. If the double vision is still present with one eye occluded, then this is "monocular diplopia" and rarely neurologically threatening. Most causes of monocular diplopia are optical: astigmatism, cataracts, macular pucker etc. However, if the double vision disappears with either eye covered, this is potentially more serious.