Contact lens-related keratitis more common with extended wear

SAN DIEGO – Contact lens-related microbial keratitis (MK) is more prevalent in extended-wear contact lenses, with no significant differences between silicone hydrogels and conventional lenses, according to a study presented here at the annual Academy of Optometry meeting Saturday. The study, presented by Fiona Stapleton of the University of South Wales, was aimed at understanding the risk factors associated with CL-related MK.

"We're talking about a rare but severe disease," Dr. Stapleton said. "We aimed to identify all new cases and identify the risk factors."

In this study, researchers looked at new cases of CL-related MK seen by ophthalmic practitioners in Australia between January 2003 and March 2004. These cases were reported via Internet, postal mail or fax. Cases were classified by severity, and telephone interviews were conducted to gather demographic, contact lens and hygiene information. A total of 307 eligible cases of CL-related MK were documented, and 1,373 controls were identified, with 8.5% wearing daily disposable contacts, and 10.2% using silicone hydrogels (6.0 % on a daily wear and 4.2% on an extended wear basis.)

After a preliminary analysis, it was found that the annualized incidence of all CL-related MK was 5.1 (95% CI 4.1-6.7) per 10,000 wearers. In subjects wearing daily disposable contact lenses, the annual occurrence of moderate and severe keratitis was 0.9. In daily wear soft contact users, the incidence was 3.1, and in daily wear silicone hydrogel users the incidence was 4.5. Among extended wear soft contact lens users, the incidence was 11.7, and in extended wear silicone hydrogel users the incidence was 19.3 per 10,000 wearers.