Noninfectious ring-shaped keratitis associated with Pseudomonas aeruginosa.

Ring-shaped keratitis appeared in the left eye of a 37-year-old woman who had worn soft contact lenses for more than five years. The corneal ring began to appear within seven days of a central corneal abrasion. Gram staining of the patient's contact lens cleaning solution showed many gram-negative rods, and microbiologic investigations of the patient's soft contact lens and contact lens case disclosed Pseudomonas aeruginosa. There was no clinical or laboratory evidence of an infectious process. Prompt treatment with polymyxin B-bacitracin ointment and prednisolone acetate 1% eyedrops led to resolution of the opacity and a return to the patient's normal visual acuity. The P. aeruginosa endotoxin may have been transferred through the epithelial break into the superficial corneal stroma, leading to ring formation via endotoxin-initiated, properdin-mediated, antibody-independent complement activation.