Bacterial populations on silicone hydrogel and hydrogel contact lenses after swimming in a chlorinated pool

Abstract

Purpose: A number of reports have indicated an association between swimming with contact lenses and subsequent eye infection. This study tests whether a hydrophilic contact lens worn while swimming accumulates bacteria present in the water. It was of interest to determine if lens type (silicone hydrogel versus hydrogel) affected the result. Methods: Fifteen healthy non-contact lens wearers swam for 30 minutes with a silicone hydrogel lens (Purevision) on one eye and a hydrogel lens (Acuvue 2) on the other. Lenses were removed aseptically and placed in sterile vials five minutes after the subjects left the water. Microbial growth was enumerated for total numbers of colonies and categorized by species present. Numbers of colonies were compared between the two lens groups, and with a water sample taken from the pool at the time of the experiment. Eight of the subjects returned on a different day and wore new lenses for thirty minutes under normal room conditions. Results: Two lenses were lost while swimming. 27 of the remaining 28 lenses worn while swimming showed colonization, principally with Staphylococcus epidermidis, which was also by far the most common species identified from the water itself. Small numbers of Staphylococcus aureus and Streptococcus salivarus were also present in both the water and on the lenses. Numbers of colonies varied among subjects (range 0-230), but no differences were observed between the two lens groups. Lenses removed after thirty minutes of wear without swimming were mostly sterile, with 3 of the 16 lenses showing just two colonies each. Conclusion: It appears that wearing a hydrophilic lens while swimming allows accumulation of microbial organisms on, or in, the lens, regardless of lens material. Swimmers should be advised to wear tight fitting goggles if lenses are worn while swimming, and thorough disinfection of the lenses prior to overnight wear seems prudent