Contact Lens & Anterior Eye
Volume 30, Issue 4 , Pages 223-232 , September 2007

Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: Methods and findings to date

  • H. Wagner

      Affiliations

    • Nova Southeastern University, College of Optometry, Ft. Lauderdale, FL, United States
    • ,
  • J.T. Barr

      Affiliations

    • The Ohio State University College of Optometry, 338 West Tenth Avenue, Columbus, OH 43210, United States
    • ,
  • K. Zadnik

      Affiliations

    • The Ohio State University College of Optometry, 338 West Tenth Avenue, Columbus, OH 43210, United States
    • Corresponding Author InformationCorresponding author. Tel.: +1 614 292 6603; fax: +1 614 292 4705.
    • ,
  • the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group

References 

  1. Korb DR, Finnemore VM, Herman JP. Apical changes and scarring in keratoconus as related to contact lens fitting techniques. J Am Optom Assoc. 1982;53:199–205
  2. Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998;42:297–319
  3. Krachmer JH, Feder RS, Belin MW. Keratoconus and related non-inflammatory corneal thinning disorders. Surv Ophthalmol. 1984;28:293–322
  4. Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol. 1986;101:267–273
  5. Barr JT, Gordon MO, Zadnik K, Pellican K, Edrington TB. Photodocumentation of corneal scarring Collaborative Longitudinal Evaluation of Keratoconus Study group. J Refract Surg. 1996;12:492–500
  6. Davis LJ, Schechtman KB, Begley CG, Shin JA, Zadnik K the CLEK Study group. Repeatability of refraction and corrected visual acuity in keratoconus. Optom Vis Sci. 1998;75:887–896
  7. Raasch TW, Schechtman KB, Davis LJ, Zadnik K the CLEK Study group. Repeatability of subjective refraction in myopic and keratoconic subjects: results of vector analysis. Ophthal Physl Opt. 2001;21:376–383
  8. Gordon MO, Schechtman KB, Davis LJ, McMahon TT, Schornack J, Zadnik K. Visual acuity repeatability in keratoconus: impact on sample size. Optom Vis Sci. 1998;75:249–257
  9. Edrington TB, Szczotka LB, Begley CG, Burger DS, Wilson BS, Barr JT, et al. Repeatability and agreement of two corneal-curvature assessments in keratoconus: keratometry and the first definite apical clearance lens (FDACL). Cornea. 1998;17:267–277
  10. Bailey IL, Lovie JE. New design principles for visual acuity letter charts. Am J Optom Physiol Opt. 1976;53:740–745
  11. Ferris FL, Kassoff A, Bresnick GH, Bailey I. New visual charts for clinical research. Am J Ophthalmol. 1982;94:91–96
  12. Mandell RB. Corneal topography. Springfield, IL: Charles C. Thomas; 1988;
  13. Edrington TB, Barr JT, Zadnik K, Davis LJ, Gundel RE, Libassi DP, et al. Standardized rigid contact lens fitting protocol for keratoconus. Optom Vis Sci. 1996;73:369–375
  14. Zadnik K, Barr JT, Edrington TB, Everett DF, Jameson M, McMahon TT, et al. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Invest Ophthalmol Vis Sci. 1998;39:2537–2546
  15. Zadnik K, Steger-May K, Fink BA, Joslin CE, Nichols JJ, Rosenstiel CE, et al. Between-eye asymmetry in keratoconus. Cornea. 2002;21:671–679
  16. Nichols JJ, Steger-May K, Edrington TB, Zadnik K the CLEK Study group. The relation between disease asymmetry and severity in keratoconus. Br J Ophthalmol. 2004;88:788–791
  17. Edrington TB, Szczotka LB, Barr JT, Achtenberg JF, Burger DS, Janoff AM, et al. Rigid contact lens fitting relationships in keratoconus. Optom Vis Sci. 1999;692–699
  18. Edrington TB, Gundel RE, Libassi DP, Wagner H, Pierce GE, Walline JJ, et al. Variables affecting rigid contact lens comfort in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Optom Vis Sci. 2004;81:182–188
  19. Zadnik K, Barr J, Edrington TB, Nichols JJ, Wilson BS, Siegmund K, et al. Corneal scarring and vision in keratoconus: a baseline report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Cornea. 2000;19:804–812
  20. Barr JT, Zadnik K, Wilson BS, Edrington TB, Everett DF, Fink BA, et al. Factors associated with corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Cornea. 2000;19:501–507
  21. Zadnik K, Barr JT, Steger-May K, Edrington TB, McMahon TT, Gordon MO. Comparison of flat and steep rigid contact lens fitting methods in keratoconus. Optom Vis Sci. 2005;82:1014–1021
  22. Kymes SM, Walline JJ, Zadnik K, Gordon MO the CLEK Study group. Quality of life in keratoconus. Am J Ophthalmol. 2004;138:527–535
  23. Davis LJ, Schechtman KB, Wilson BS, Rosenstiel CE, Riley CH, Libassi DP, et al. Longitudinal changes in visual acuity in keratoconus. Invest Ophthalmol Vis Sci. 2006;47:489–500
  24. McMahon TT, Edrington TB, Szczotka-Flynn LB, Olafsson HE, Davis LJ, Schechtman KB, et al. Longitudinal changes in corneal curvature in keratoconus. Cornea. 2006;25:296–305
  25. Barr JT, Wilson BS, Gordon MO, Rah MJ, Riley C, Kollbaum PS, et al. Estimation of the incidence and factors predictive of corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study. Cornea. 2006;25:16–25
  26. Zadnik K, Wilson BS, Gordon MO, the CLEK Study group. Age in keratoconus, 2006; ARVO Abstract #2951, http://www.arvo.org, accessed 09/15/06.

PII: S1367-0484(07)00036-7

doi: 10.1016/j.clae.2007.03.001

Contact Lens & Anterior Eye
Volume 30, Issue 4 , Pages 223-232 , September 2007

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