The hospitalized cases of contact lens induced keratitis in Sweden and their relation to lens type and wear schedule: results of a three-year retrospective study.

All hospitalized cases of contact lens induced keratitis with stromal involvement among cosmetic wearers in Sweden over a 3-year period were reviewed for risk factors in relation to lens type and wear schedule. Information on every case was obtained from ophthalmology departments. Lens type and wear schedule were identified. The number of lens wearers, subdivided by lens type and wear schedule, was obtained from a study by the Swedish Contact Lens Association. Annual incidence figures were then calculated as expressions of risk factors. There were 30.7 cases per year, on average, of hospitalized lens induced keratitis in Sweden. The annual incidence per 10,000 wearers was 0.51 for daily wear and 3.12 for extended wear of conventional soft lenses, 0.16 for daily wear and 4.17 for extended wear of disposable soft lenses, and 1.21 for daily wear of rigid gas permeable lenses. It may be concluded that daily wear of disposable lenses was associated with significantly (P < 0.05-0.01) less risk of hospitalized keratitis than daily wear of the other lens types. Extended wear of conventional and disposable soft lenses showed a significantly (P < 0.01-0.001) higher risk of hospitalized keratitis than daily wear. However, the two extended wear groups did not differ significantly (P > 0.2). Microbial keratitis was significantly (P < 0.001) more common than sterile (no growth of microbes) keratitis among conventional soft lens wearers, whereas the opposite was true (P < 0.05) among disposable lens wearers.