Infectious keratitis: correlation between corneal and contact lens cultures.

Objective: This article reports a study of the effectiveness of performing contact lens cultures to identify causative organisms of infectious keratitis in patients using extended-wear soft contact lenses (cosmetic or therapeutic).

Methods: Patients' records from the Ocular Microbiology Laboratory of the Department of Ophthalmology, Paulista School of Medicine, from 1976 to 2000, and data of patients with contact lens-related keratitis in which the contact lens had been cultured were collected and reviewed.

Results: One hundred thirteen patients were included. Only soft contact lenses had been cultured and 29.2% of them were therapeutic contact lenses. An overall concordance of 84.0% was found between cultures obtained from corneal scrapings and contact lenses, with a higher rate in fungal keratitis (100%) compared to amebic (80.0%) and bacterial (74.5%) keratitis. In cases of concomitant bacterial growth in cultures of scrapings and contact lenses, the same organism was detected in 97.04%. Most cases of bacterial infection were caused by Pseudomonas spp. Among the discordant cases (16%), a microorganism was more likely to be isolated by contact lens culture (94.4%).

Conclusions: Contact lens cultures may identify the causative organisms in most cases of contact lens-related keratitis. The clinical relevance of positive contact lens cultures in keratitis with negative corneal cultures needs further investigation.