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Risk factors for microbial keratitis with contemporary contact lenses: a case-control study
J K G Dart1, C F Radford, D Minassian
1Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom. j.dart@ucl.ac.uk
Objective:
To assess the relative risks (RR) of microbial keratitis (MK) for contemporary contact lens (CL) types and wearing schedules.
Design:
A 2-year prospective case-control study begun in December 2003.
Participants:
Cases were 367 CL wearers attending Moorfields Eye Hospital with proven or presumed MK. Controls were 1069 hospital controls, who were CL wearers with a disorder unrelated to CL wear, and 639 population-based controls who were CL wearers randomly selected from the Moorfields catchment area. Hospital patients completed a self-administered questionnaire; population-based controls were interviewed by telephone.
Testing:
Multivariate analysis was done both for all cases of MK, and for the moderate and severe MK subgroups alone.
Main Outcome Measures:
The RR for developing MK, and vision loss, for all lens types compared with planned replacement soft lenses (the referent).
Results:
Compared with planned replacement soft lenses (the referent), the RR of MK was significantly increased with daily disposable (DD) CLs (RR, 1.56x [95% confidence interval (CI), 1.1-2.1]; P = 0.009) and differed between different brands of DD lens, was reduced for rigid lenses (RR, 0.16x [95% CI, 0.06-0.4]; P<0.001), and no different for silicone hydrogel or other types of soft lens. Although the risk of MK was higher overall among DD lens users, the risk of vision loss was less than for planned replacement soft CL users (P = 0.05); no DD lens users lost vision to the level of >or=20/40. The RR for overnight wear, for any lens type, was 5.4 times higher (95% CI, 3.3-10.9; P<0.001). Comparison of the DD soft CL types with planned replacement soft lenses (the referent), showed significant differences between brands for the risk of MK.
Conclusions:
The risk of MK has not been reduced in users of DD and silicone hydrogel CLs. However, vision loss is less likely to occur in DD than in reusable soft CL users. Different brands of CL may be associated with significantly different risks of keratitis; understanding these differences should lead to the development of safer soft lenses. These findings suggest that lens/ocular surface interactions may be more important in the development of corneal infection than oxygen levels and CL case contamination.
Insights
Daily disposable contact lenses (CLs) show increased microbial keratitis (MK) risk, but reduced vision loss compared to reusable soft CLs. Overnight wear significantly elevates MK risk across all lens types.
Area of Science:
- Ophthalmology
- Microbiology
- Biomaterials Science
Background:
- Microbial keratitis (MK) is a significant risk associated with contact lens (CL) wear.
- Understanding the relative risks of contemporary CL types and wearing schedules is crucial for patient safety and clinical guidance.
Purpose of the Study:
- To evaluate the comparative risks of microbial keratitis (MK) and associated vision loss for various types of contact lenses (CLs) and wearing patterns.
- To identify specific CL characteristics or usage behaviors that influence the risk of MK.
Main Methods:
- A 2-year prospective case-control study involving 367 MK cases and 1069 hospital-based and 639 population-based CL-wearing controls.
- Data collected via self-administered questionnaires and telephone interviews.
- Multivariate analysis performed to assess relative risks (RR) for MK and vision loss across different CL types and wearing schedules, using planned replacement soft lenses as the referent group.
Main Results:
- Daily disposable (DD) CLs showed a 1.56x increased RR of MK compared to planned replacement soft lenses, with significant brand variations.
- Rigid gas permeable lenses demonstrated a reduced RR of MK (RR, 0.16x).
- Overnight wear of any CL type increased the RR of MK by 5.4 times. DD CL users experienced less vision loss than planned replacement soft CL users.
Conclusions:
- The risk of MK has not decreased with daily disposable or silicone hydrogel CLs.
- Despite increased MK risk, daily disposable CLs are associated with a lower likelihood of vision loss.
- Lens-brand specific differences in keratitis risk highlight the importance of lens-ocular surface interactions over factors like oxygen permeability or case contamination.
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