A summary of the findings from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. CLEK Study Group.

BACKGROUND: This summary of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study includes the study design and results to date. METHODS: The CLEK Study is a longitudinal, observational study of 1,209 patients with keratoconus. The study's main outcome measures are corneal scarring, visual acuity, corneal curvature, and quality of life. RESULTS: These patients' mean age at baseline was 39.3 +/- 10.9 years, and they had moderate to severe keratoconus. Ninety-five percent of the patients had steep keratometric readings of at least 45 D, and 78% had best-corrected visual acuity of 20/40 or better in both eyes. Sixty-five percent of the patients wore rigid gas-permeable contact lenses in both eyes, and most of those (73%) reported that their lenses were comfortable. Most rigid gas-permeable contact lens wearers were fitted with apical touch (88%). Fifty-three percent had corneal scarring in one or both eyes, and corneal scarring was associated with corneal staining, contact lens wear, age, the presence of a Fleischer's ring, and a steeper cornea. Corneal scarring was associated with decreased high- and low-contrast visual acuity. CONCLUSIONS: These results characterize keratoconus patients as rigid gas-permeable contact lens wearers with moderately steep corneas. Corneal scarring is associated with decreased vision in keratoconus.