A corneal ulcer is an infection of the cornea, the clear, “windshield-like” tissue on the surface of the eye. The severity of corneal ulcers ranges from mild to severe, often depending on the pathogen involved. Risk factors for corneal ulcers include: contact lens use, ocular trauma, previous eye surgery, underlying corneal problems and poor eyelid closure. While mild corneal ulcers can often be treated with topical antibiotics, more severe ulcerations need to be cultured in a lab to determine the exact pathogen and treated with specially-made fortified antibiotics. Corneal ulcers can leave permanent, visually significant scars on the cornea and should be evaluated urgently by an ophthalmologist.