Corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: Baseline prevalence and repeatability of detection

Purpose, The multicenter Collaborative Longitudinal Evaluation of Keratocon us (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the prevalence of corneal scarring in these patients . We also report on the test-retest repeatability of corneal scar documenta tion at the slit-lamp biomicroscope by trained clinicians and by masked pho tograph readers and on the scarring-status agreement at baseline between cl inicians and photograph readers. Methods. Clinicians and masked photograph readers graded each cornea as to scarring status. Patients were examined by clinicians, and their corneas were photographed at baseline (2,297 nongraf ted eyes of 1,209 patients) and at a repeated visit (258 nongrafted eyes of 138 patients). These photographs were evaluated by the masked readers at t he CLEK Photography Reading Center (CPRC). Clinicians reported corneal scar s in right eyes at baseline as "definitely not present" in 53.9%, "probably not present" in 8.4%, "probably present" in 8.2%, and "definitely present" in 29.4% of patients. A weighted kappa statistic of 0.83 (95% confidence i nterval from 0.78 to 0.88) indicates that agreement is excellent between ba seline and repeated assessments for the presence of a corneal scar by clini cians. Results, Agreement is very good between baseline and repeated photog raph-reader assessments for the presence of a scar, with a weighted kappa o f 0.77 (95% confidence interval, 0.72-0.82). The kappa statistic comparing photograph-reader scarring assessments with clinician results was 0.69 (95% confidence interval, 0.66-0.71). Conclusion, The data also suggest better agreement between clinicians and readers when Vogt's striae and corneal ner ves were observed. The data also suggest better agreement when corneal stai ning was not observed by the photograph readers. The CLEK Study protocol fo r determining the presence of scars is highly repeatable.