Risk Factors for Bacterial Keratitis and Severe Disease in Hydrogel Contact Lens Users: A Multicenter Case-Control Study and Case-Only Analysis

Purpose: To assess risk factors for contact lens (CL)-related bacterial keratitis, cases and high-risk controls were enrolled. Using high-risk controls can help elucidate whether certain CL types or modalities are attributable to disease burden if risky wear patterns are similar between the cases and controls. This analysis identified whether such CL factors were associated with the occurrence of bacterial keratitis. In addition, a case-only analysis determined CL factors associated with severe disease.

Methods: From 2018 to 2021, 158 controls were enrolled at University Hospitals of Cleveland Eye Institute, and 153 bacterial keratitis cases were enrolled across 14 sites in the United States. Cases were soft CL wearers with either culture-proven bacterial keratitis or a corneal infiltrate with an overlying epithelial defect within the central 4 mm of the cornea, uveitis, or significant pain. Fungal, protozoan, or nonsoft CL wear-related microbial keratitis cases were excluded. Controls were recruited from high-risk CL wearers with no history of disease. All participants completed a questionnaire related to demographics, type of CL used, wearing schedule, lens handling practices, and storage case handling. Cases with ulcer/infiltrate size ≥2 mm in size, presence of hypopyon, or had fortified antibiotics prescribed were classified as severe keratitis. Univariate and multivariable logistic regression was used to assess association of CL variables with the occurrence of bacterial keratitis as well as occurrence of severe disease among the cases only.

Results: Compared with the control cohort, cases were older (mean age 45.6 vs. 38.9 years), had more males (42.5% vs. 23.6%), and had more current or former smokers (41.7% vs. 12.9%). There were no significant associations between CL material (silicone hydrogel vs. not) or CL type (daily disposable vs. reusable) and occurrence of bacterial keratitis. More than two-thirds (67.3%) of cases were classified as severe. Among cases only, univariate analyses found current smokers to have increased risk of severe disease (OR=2.87; 95% CI 1.13-7.26, P =0.03). Adjusting for age, sex, and smoking among the cases only, daily disposable lenses were protective against severe disease (OR=0.32; 95% CI 0.11-0.89, P =0.03). Reusable lenses increased risk of severe microbial keratitis between 3.0- and 4.4-fold compared with compliant daily disposability.

Discussion/conclusion: Compared with a high-risk control cohort, no specific lens factors were associated with occurrence of CL-associated bacterial keratitis. Among cases only, current smokers and patients wearing reusable lenses are at increased risk of severe keratitis. Daily disposable lenses were protective even when noncompliance to daily disposability was considered.