Microbial keratitis in prospective studies of extended wear with disposable hydrogel contact lenses

Purpose: To report the annualized incidence of microbial keratitis with extended wear of low oxygen transmissible (Dk/t) disposable soft contact lenses from prospective postmarket clinical trials. Methods: Seven hundred ninety subjects were enrolled at the L.V. Prasad Eye Institute (LVPEI), Hyderabad, India from March 1993 to March 2000, resulting in 1231 patient eye years, and 167 subjects were enrolled at the Cornea and the Contact Lens Research Unit (CCLRU), Sydney, Australia from July 1987 to December 1999, resulting in 842 patient eye years. Results: The annualized incidence of microbial keratitis per 10,000 eyes per year of lens wear was 32.5 (95% CI 8.9 to 83.2) for LVPEI, 23.8 (95% CI = 2.9 to 85.8) for CCLRU; when data are combined across both centers, the incidence was 28.9 (95% CI = 10.6 to 63) per 10,000 eyes per year of lens wear. This equates to 57.0 per 10,000 wearers or 1 in 173 wearers per year of lens wear. All events were rated as slight to moderate in severity and did not result in visual loss. Two events were described to highlight the challenges in diagnosis and treatment of microbial keratitis. Conclusions: The incidence of microbial keratitis with extended wear of low-Dk/t disposable lenses was higher in these prospective studies (1 in 210 wearers per year at CCLRU and 1 in 154 wearers per year at LVPEI) than that seen in retrospective population-based surveillance studies (1 in 500 wearers per year). Practitioners and patients should always be alert to signs and symptoms, and practitioners should adopt conservative strategies for diagnosis and management of contact lens-related adverse events.