Longitudinal changes in corneal curvature in keratoconus

Timothy T. McMahon, Timothy B. Edrington, Loretta Szczotka-Flynn, Harald E. Olafsson, Larry J. Davis, Kenneth B. Schechtman, Karla Zadnik

Research output: Contribution to journalArticlepeer-review

115 Scopus citations


Purpose: This study was designed to identify factors that predict longitudinal increases in corneal curvature as measured by the First Definite Apical Clearance Lens (FDACL) and flatter keratometric reading (Flat K) in keratoconus. Methods: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a long-term evaluation of the natural history of keratoconus involving 1209 patients. This report uses 8 years of follow-up data from 1032 patients who had penetrating keratoplasty in neither eye at baseline and who provided enough data to compute the slope of the change with time in the FDACL or the Flat K. Outcome measures included the aforementioned slopes and whether the FDACL or the Flat K increased by 3.00 or more diopters (D) in at least 1 eye. Results: At CLEK Study entry, patients were aged 38.9 ± 10.8 years. Overall, 44.3% of them were women, and 69.3% of them were white. The slope of the change in FDACL (0.18 ± 0.60 D/y) and Flat K (0.20 ± 0.80 D) during 8 years translates into expected 8-year increases of 1.44 D in FDACL and 1.60 D in Flat K. Increases of ≥3.00 D in either eye had an 8-year incidence of 24.8% for FDACL and 24.1% for Flat K. Independent predictors of increased FDACL included younger age, poorer baseline high-contrast manifest refraction visual acuity, and non-white race. Younger age and poorer high-contrast manifest refraction visual acuity were independent predictors of a >3.00-D increase for both FDACL and Flat K. Conclusion: CLEK patients exhibited a slow but clear increase in corneal curvature. Younger age and poorer high-contrast manifest refraction visual acuity at baseline predicted the rate of change in corneal curvature.

Original languageEnglish
Pages (from-to)296-305
Number of pages10
Issue number3
StatePublished - Apr 2006


  • Age
  • Corneal curvature
  • First Definite Apical Clearance
  • Keratoconus
  • Keratometry


Dive into the research topics of 'Longitudinal changes in corneal curvature in keratoconus'. Together they form a unique fingerprint.

Cite this