The annualized incidence of contact lens induced keratitis in Sweden and its relation to lens type and wear schedule: results of a 3-month prospective study.

All cases of contact lens induced keratitis (epithelial defects with an underlying infiltrate or ulcer) among cosmetic wearers in Sweden were collected in a 3-month prospective study and analyzed for risk factors in relation to lens type and wear schedule. Every ophthalmologist in Sweden was invited to participate and 100% responded. Viral cases were excluded. The number of lens wearers in Sweden, subdivided by lens type and wear schedule, was obtained in a parallel 3-month study among 71% of the lens fitters, who counted all their wearers, recording lens type and wear schedule as well as revisit and replacement schedules. The annualized incidence per 10,000 wearers was 1.48 for daily wear of rigid gas permeable lenses, 2.16 for daily wear and 10.00 for extended wear of disposable soft lenses, and 2.17 for daily wear and 13.33 for extended wear of conventional soft lenses. Thus, extended wear was associated with a significantly (P < 0.01-0.001) higher (5-6 times) risk of keratitis than daily wear. There were no other significant differences between the incidence figures. The Swedish incidence figures were approximately half as high as those reported in the U.S. Of the lesions, only 12% were located within the pupillary area and only 8% were corneal ulcers. Only three patients (12%) suffered a decrease in visual acuity. Severe keratitis was significantly (P < 0.01) more common among conventional soft lens wearers (accounting for all ulcers, all lesions within the pupillary area, and all decreases in visual acuity) than among wearers of disposable lenses.