Baseline findings in the collaborative longitudinal evaluation of keratoconus (CLEK) study

Karla Zadnik, Joseph T. Barr, Timothy B. Edrington, Donald F. Everett, Mary Jameson, Timothy T. McMahon, Julie A. Shin, John L. Sterling, Heidi Wagner, Mae O. Gordon

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447 Scopus citations


PURPOSE. To describe the baseline findings in patients enrolled in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study. METHODS. This is a longitudinal observational study of 1209 patients with keratoconus enrolled at 16 clinical centers. Its main outcome measures are corneal scarring, visual acuity, keratometry, and quality of life. RESULTS. The CLEK Study patients had a mean of 39.29 ± 10.90 years with moderate to severe disease, assessed by a keratometric-based criterion (95.4% of patients had sleep keratometric readings of at least 45 D) and relatively good visual acuity (77.9% had best corrected visual acuity of at least 20/40 in both eyes). Sixty-five percent of the patients wore rigid gas-permeable contact lens, and most of those (73%) reported that their lenses were comfortable. Only 13.5% of patients reported a family history of keratoconus. None reported serious systemic diseases that had been previously reported to be associated with keratoconus. Many (53) reported a history of atopy. Fifty- three percent had corneal scarring in one or both eyes. CONCLUSIONS. Baseline findings suggest that keratoconus is not associated with increased risk of connective tissue disease and that most patients in the CLEK Study sample represent mild to moderate keratoconus. Additional follow-up of at least 3 years will provide new information about the progression of keratoconus, identify factors associated with progression, and assess its impact on quality of life.

Original languageEnglish
Pages (from-to)2537-2546
Number of pages10
JournalInvestigative Ophthalmology and Visual Science
Issue number13
StatePublished - Dec 1998


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