research in practice

Modifying MK Risk

Research reveals factors associated with microbial keratitis.

MILE BRUJIC, O.D.,

CRYSTAL BRIMER, O.D.

Microbial keratitis (MK) is diagnosed in three to five of 10,000 daily contact lens (CL) wearers per year, meaning one or more of these patients could appear in your chair.^1,2,3

A recent study shows modifiable risk factors for moderate and severe MK in daily wear CL patients.³

Supporting research

Risk factors, such as storage case hygiene, storage case replacement frequency, intermittent over- night usage, smoking and high socioeconomic class, were implicated in moderate and severe MK in daily CL wearers.³

Specifically, failing to air dry the storage case after each use increased MK risk 6.4 times. Not replacing the storage case at least every six months increased MK risk 5.4 times.

A corneal ulcer as seen via fluorescein dye, cobalt blue light and a #12 wratten filter.

Also, occasional overnight wear (more than once per month but less than once per week) increased MK risk 6.5 times. Further, high socioeconomic class and smoking impacted MK risk (4.1x and 3.7x, respectively). Age, gender and lens type had no impact.

Each MK case was evaluated for severity using corneal culture, central location, accompanying uveitis, pain and vision loss.

A total of 90 patients through 12 months were diagnosed with moderate or severe MK associated with daily CL wear and were compared with 1,090 community controls.

Phone interviews surveyed all participants’ demographics, lens type and wear history, lens and case hygiene and other environmental factors, such as climate zone. Eligible participants were ages 15 to 64 and had mild refractive error and had worn daily wear CLs for at least four weeks prior.

Implications for patient care

Biofilm within the CL storage case is resilient despite proper lens cleaning and disinfecting.⁴ This likely explains why poor lens hygiene itself does not increase moderate and severe MK risk, but is a risk factor for overall MK incidence (including mild cases). It also clarifies why daily disposable CLs decrease MK occurrence.³

Extended wear has been shown a hazard for ulcerative keratitis, likely due to physiological changes and the bacterial bioburden in the cornea.^5,6 However, because all study participants slept in their lenses less than one night per week, the increased risk may be more closely linked to the subjects’ likelihood of other risky behaviors rather than any physiological impact.

The same may be true of the associated risk of smoking.

The risk factor of higher socioeconomic class is intriguing and may also be linked to a specific behavior or attitude, but remains unexplained.

Based on these findings, we, as eyecare practitioners, should review the importance of lens case hygiene, replacement, the dangers of overwear and smoking at each and every appointment with our CL-wearing patients.

Being truly diligent with this could have a dramatic effect on our CL-wearing patients’ eye health and safety. OM

1. Cheng KH, Leung SL, Hoekman HW, et al. Incidence of contact-lens-associated microbial keratitis and its related morbidity. Lancet. 1999 Jul 17;354 (9174): 181-5.

2. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008 Oct;115(10):1655-62. Epub 2008 Jun 5.

3. Stapleton F, Edwards K, Keay L, et al. Risk factors for moderate and severe microbial keratitis in daily wear contact lens users. Ophthalmology. 2012 Aug; 119(8):1516-21. Epub 2012 Apr 21.

4. Dannelly HK, Waworuntu RV. Effectiveness of contact lens disinfectants after lens storage. Eye Contact Lens 2004 Jul;30:163-5.

5. Schein OD, Glynn RJ, Poggio EC, et al, Microbial Keratitis Study Group. The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses: a case-control study. N Engl J Med 1989 Sep 21;321:773-8.

6. Szczotka-Flynn LB, Bajaksouzian S, Jacobs MR, Rimm A. Risk factors for contact lens bacterial contamination during continuous wear. OptomVis Sci. 2009 Nov;86(11):1216-26.

DR. BRUJIC IS A PARTNER OF PREMIER VISION GROUP, A FOUR-LOCATION OPTOMETRIC PRACTICE IN NORTHWEST, OHIO. HE HAS A SPECIAL INTEREST IN GLAUCOMA, CONTACT LENSES AND OCULAR DISEASE MANAGEMENT OF THE ANTERIOR SEGMENT. E-MAIL HIM AT BRUJIC@PRODIGY.NET.

DR. BRIMER OWNS CRYSTAL VISION SERVICES, AN OPHTHALMIC EQUIPMENT AND PRACTICE MANAGEMENT CONSULTING COMPANY. SHE PRACTICES IN WILMINGTON, NC AND HAS A SPECIAL INTEREST IN CONTACT LENSES AND DRY EYE MANAGEMENT. E-MAIL HER AT DRBRIMER@CRYSTALVISIONSERVICES.COM, OR SEND COMMENTS TO OPTOMETRICMANAGEMENT@GMAIL.COM.