A review of relative risks associated with four types of contact lenses

This paper reviews the data of Frank et al. in the light of increasing concern over the safety of contact lenses used for extended wear. Relative risks were calculated for four types of contact lenses (CLs): extended wear soft, daily wear soft, rigid gas-permeable (RGP), and polymethylmethacrylate (PMMA) lenses--worn by a group of patients who presented themselves for emergency ocular treatment. The cases comprised 329 CL wearers who were found to have lens related metabolic disorders, toxic or hypersensitivity reactions, cornea abrasions, microbial keratitis, or some other lens-induced problem. Controls comprised 64 CL wearers whose ocular problems were unrelated to lens use. It was found that extended wear soft lenses were nearly 7 times more likely to be associated with an ocular disorder than PMMA hard lenses, and approximately 3.4 times more likely than daily wear soft lenses. Furthermore, extended wear soft lenses were nearly 5 times more likely to be linked with microbial keratitis than daily wear soft lenses, and approximately 7.5 times more likely than RGP lenses. Metabolic disorders were also more common with extended wear lenses (relatively risk: 3.3) than with either RGP (1.8) or daily wear soft lenses (2.0) or PMMA lenses (1.0). If the association between extended wear soft lenses and ocular complications is borne out in large population studies, eye-care professionals may need to reconsider the wisdom of prescribing these lenses for the cosmetic correction of vision.