Risk Factors for Moderate and Severe Microbial Keratitis in Daily Wear Contact Lens Users
Stapleton F, Edwards K, Keay L, et al
Stapleton and colleagues prospectively collected new cases of daily wear contact lens-related microbial keratitis from all ophthalmologists and optometrists in Australia over the 12-month period from October 2003 to September 2004. Keratitis was defined as a positive corneal culture or an infiltrate and overlying epithelial defect with 1 or more of the following: any part involving the central 4 mm of the cornea, uveitis, or pain. Control individuals (n = 1090) were identified through a population-based telephone survey. Numerous risk factors were considered, including demographic characteristics, lens details, lens and case hygiene, lens wear history, water exposure, and other behaviors and environmental factors. Patients who wore their lenses overnight once a week or more were considered extended-wear lens users and were therefore excluded from the study. Keratitis was divided into mild, moderate, and severe.
The investigators identified 125 cases of microbial keratitis, 90 of which were moderate to severe. Cultures were obtained from 63 cases, and 41 (63%) were positive (30 gram-negative bacteria, 9 gram-positive bacteria, and 2 acanthamoeba). Significant risk factors for moderate and severe keratitis in the daily wear lens users included occasional overnight use (more than once a month but less than once a week, because more than once a week was an exclusion criterion), poor lens case hygiene (failure to air-dry the storage case after use), smoking, high socioeconomic class, use of a multipurpose no-rub cleaning solution, and lens case replacement less than every 6 months.
Overnight wear of soft contact lenses has long been known to increase the risk for microbial keratitis. In fact, it continues to amaze me that in 2012, television commercials still tout the safety of extended-wear soft contact lenses. This study looked at risk factors for microbial keratitis in daily-wear soft contact lens users. The investigators performed a national surveillance study of all eye care doctors in Australia over a 12-month period. They assessed a wide variety of risk factors in 125 patients with infections compared with 1090 control patients.
Of interest, age and sex were not significant risk factors. Risk factors for moderate to severe infectious keratitis included the following:
Poor lens hygiene (6.4 times increased risk vs good hygiene);
Replacing the lens storage case less often than every 6 months (5.4 times increased risk vs every-3-month replacement);
Occasional overnight use of lenses (6.5 times increased risk);
High socioeconomic status (4.1 times increased risk); and
Smoking (3.7 times increased risk).
The investigators calculated that almost 50% of all cases of moderate to severe microbial keratitis could be eliminated by better lens case hygiene and 27% by frequent replacement of lens storage cases. These 2 issues are easily modifiable risk factors. Occasional overnight wear should be somewhat modifiable. Smoking has been much harder to deal with, although increased risk for a moderate to severe corneal ulcer in contact lens wearers can be added to the many other benefits of stopping smoking. No good explanation was offered for why high socioeconomic class should increase the risk for infectious keratitis, especially when previous studies have identified lower socioeconomic class as a risk factor.
The bottom line is that although soft contact lens wear has inherent risk, several strong risk factors for the worst complication (microbial keratitis) can be relatively easily modified. All contact lens prescribers and all eye care professionals who treat patients who wear soft contact lenses should teach and reinforce the following at each visit:
Replace the contact lens storage case at least every 3 months;
Air-dry the contact lens case when not in use; and
No overnight wear.
All patients should be asked about smoking and encouraged to quit. It is noteworthy that 6% of the patients with infection and 12% of the control participants in this study used daily disposable soft contact lenses, further supporting the fact that poor lens care and overnight wear are bad. However, wearers of daily disposable soft contact lenses can still get infectious keratitis.
In our cornea practice at Wills Eye Institute, we see new contact lens-related infections several times a week. Although most are relatively mild, some are severe and cause substantial vision loss. Our current best recommendation for soft contact lens wearers is daily-wear disposable lenses. Although this study did not identify the following as significant risk factors, we recommend that patients wash their hands before handling their lenses and not swim or shower with their lenses. In addition, patients should remove their lenses if their eyes become red or painful, and they should seek urgent eye care if the symptoms persist once the lenses are removed.
Medscape Ophthalmology © 2012 WebMD, LLC
Cite this: Christopher J. Rapuano. Making Soft Contact Lens Use Safer - Medscape - Sep 18, 2012.