Estimation of the incidence and factors predictive of corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study

Purpose: The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1209 keratoconus patients. We report methods to define incident corneal scarring and baseline factors predictive of incident corneal scarring in nonsurgical eyes of CLEK Study keratoconus patients through their fifth year of follow-up. Methods: Of the 1209 patients, 878 patients with at least one unscarred cornea at baseline were included in this study. The cumulative 5-year incidence of scarring is defined as the proportion of patients who developed central corneal opacification as detected by a clinician examining the patient with a slit-lamp biomicroscope and by masked readings of corneal photographs at the CLEK Photography Reading Center. Logistic regression analysis was used to test for relationships between baseline factors and incident corneal scarring. Baseline factors analyzed included age, sex, race, atopic disease, contact lens wear, family history of keratoconus, corneal curvature, and central corneal fluorescein staining, among others. Results: The 5-year incidence of corneal scarring was 13.7% (120 of 878) overall, 16.7% (102 of 609) for contact lens-wearing eyes, and 38.0% (46 of 121) for contact lens-wearing eyes with corneal curvature greater than 52 D. Baseline factors predictive of incident scarring included corneal curvature greater than 52 D (odds ratio [OR] = 4.79; 95% confidence interval [CI], 3.08, 7.45; P < 0.001), contact lens wear (OR = 2.50; 95% CI, 1.40, 4.76; P = 0.003), marked corneal staining (OR = 2.38; 95% CI, 1.49, 3.76; P = 0.0002), and age less than 20 years (OR = 6.34; 95% CI, 2.57, 15.00; P < 0.0001). Conclusions: Multivariate analyses of 5-year prospective data from the CLEK Study cohort showed that baseline corneal curvature, contact lens wear, corneal staining, and younger age were predictive of the development of corneal scarring. The 5-year incidence of scarring is 13.7% for the overall sample and 38.0% for those eyes with corneal curvature greater than 52 D that wore contact lenses. Contact lens wear increased the risk of incident scarring more than 2-fold. These findings suggest a causal contribution of contact lens wear to corneal scarring in keratoconus and imply that corneal scarring might be reduced by modifying the contact lens fit.