A condition that occurs when bacteria builds up on the surface of the cornea. Usually caused by improperly wearing contact lenses. A corneal ulcer causes necrosis and erosion of the cornea, due to the bacterial infection.

Symptoms include extreme photophobia, pain, and loss of vision or reduced visual acuity.

If this happens to you, go see a doctor. NOW. Common treatments include antibiotics induced by eyedroppers, and steroids to increase the rate of healing.