Contributor: Gordon K. Klintworth
Corneal ulcer (ulcerative keratitis) is a common manifestation of a keratitis caused by microbes [keratitis - microbial]. Pseudomonas aeruginosa [Pseudomonas aeruginosa infection] is one of the most common bacteria causing ulcerative keratitis in the USA and many other countries in persons wearing contact lenses [contact lens - complications]. Conditions predisposing to bacterial ulcerative keratitis include contact lenses, topical corticosteroids, accidental trauma, dry eyes, trichiasis, and a poor blink reflex. An ulcer is a common lesion of the cornea. Three specific types of corneal ulcer are recognized: catarrhal ulcer [ulcer - catarrhal], ring ulcer [ulcer - ring] and Mooren ulcer. Sequeale of corneal ulcers include corneal scarring, a descemetocele, adherent leukoma and a corneal staphyloma. Corneal ulcers caused by gram-negative bacteria often have a ring shape. In such cases the ring contains C3 and properidin but not immunoglobulins according to histochemical studies. This suggest that endotoxins can stimulate the alternative pathway of complement through properidin.