A potentially devastating complication of contact lens use is microbial keratitis, which can result in vision loss as a result of corneal scarring or perforation. Cheng and colleagues conducted a community-based survey of ophthalmologists in the Netherlands to gather data on the prevalence and complications of this serious infection among contact lens wearers.

The authors sent a survey to 440 ophthalmologists who were asked to provide information on cases of microbial keratitis diagnosed during a three-month period in 1996. Responses were received from 379 of the ophthalmologists, who reported 92 cases of microbial keratitis in contact lens wearers. The types of contact lenses worn by patients who had keratitis included rigid gas-permeable lenses in 17, daily-wear soft lenses in 63 and extended-wear lenses in 12. The incidence of keratitis differed significantly among patients wearing the three different types of contact lenses. The estimated annual incidence of microbial keratitis per 10,000 users was 1.1 cases for daily-wear rigid gas-permeable lenses, 3.5 cases for daily-wear soft lenses, and 20 cases for extended-wear soft lenses. Daily-wear soft lenses were the most commonly used type of contact lens, and most (63) of the cases of microbial keratitis occurred in patients who used this type of contact lens.

Cultures were obtained in 65 cases, and the pathogen was identified in 30 (46 percent) of the 65 cases. The most common pathogens were Serratia species (eight cases), Pseudomonas aeruginosa (seven cases) and Staphylococcus species (six cases). Five patients required hospital admission, one patient underwent laser removal of corneal scars, and three patients required corneal transplantation. Final visual acuity in one patient with acanthamoeba was reduced to only light perception despite two corneal transplants. In five patients, visual acuity was reduced to 20/70 or less. The most serious cases and the greatest morbidity occurred in patients with Pseudomonas infection.

The authors conclude that the main risk factor for corneal infection in patients who use contact lenses is overnight wear, which should be strongly discouraged.