A bacterial corneal ulcer, or bacterial keratitis, is an infection of the corneal stroma that causes rapid visual loss and pain. Infectious corneal ulcers need to be treated as soon as possible to preserve vision. If left untreated, a bacterial infection can lead to perforation of the cornea, loss of vision, and even loss of the eye.

Risk factors that can lead to bacterial keratitis include contact lens wear, eye trauma, previous ocular surgery, dry eye, immunosuppression, and any other process that causes breakdown of the ocular surface.

Patients with a bacterial corneal ulcer will complain of eye pain, light sensitivity, red eyes, and possibly reduced vision. The rapidity of the onset and progression of symptoms depends on the virulence of the bacteria causing the infection.

History is very important in giving clues as to the most common organism causing the infection. Bacterial keratitis in a contact lens wearer is frequently caused by gram-negative organisms, such as Pseudomonas aeruginosa, whereas ulcers in patients with blepharitis are more commonly due to gram-positive organisms.

Note: As of August 25, 2023, the US Food and Drug Administration (FDA) is reminding the public that these recalled products should not be used due to potential bacterial contamination: EzriCare Artificial Tears, Delsam Pharma Artificial Tears, and Delsam Pharma Artificial Ointment. As of November 2023, the FDA is warning consumers not to purchase or use certain eye drops from several major brands due to risk of eye infection. Refer to the FDA list for more information. As of January 31, 2024, the FDA is warning consumers not to purchase or use South Moon, Rebright, or FivFivGo eye drops because of the potential risk of eye infection; these are copycat products easily mistaken for Bausch + Lomb's Lumify brand eye drops (an over-the-counter product approved for redness relief).