A corneal ulcer is an open sore on the cornea. It usually results from an eye infection. See your ophthalmologist immediately if you think you have a corneal ulcer. They can permanently damage your vision and even cause blindness if they are not treated. Eye drops are usually the treatment of choice. If you cannot be treated with medication, a corneal transplant can restore vision. A corneal transplant may also be needed if a scar remains after treatment with medicine.