Collaborative Longitudinal Evaluation of Keratoconus

The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Archive

The CLEK Study was a multi-center, observational study whose purpose was to prospectively characterize vision, corneal changes, and patient quality of life in Keratoconus and to determine the progression of changes occurring with Keratoconus over time.

Over 1,200 keratoconus patients were enrolled at 15 participating clinics across the United States, examined at enrollment (between May 1995 and June 1996) and annually through 8 years of follow-up (the last 8-year follow-up was completed in August 2004).

This web site, part of the official CLEK Study archive compiled after study close, contains extensive documentation of the study's protocol and procedures, detailed documentation of study forms, an introduction to the database, copies of internal newsletters and a bibliography of publications.


History and Overview


Protocol and Procedures


Study Oversight




Reading Centers


Forms and Database Documentation


Contact Information

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Last Modified: May 9, 2006
Copyright 2005