The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00000155
Recruitment Status : Unknown
Verified November 2001 by National Eye Institute (NEI).
Recruitment status was:  Active, not recruiting
First Posted : September 24, 1999
Last Update Posted : June 24, 2005
Information provided by:
National Eye Institute (NEI)

Brief Summary:

To describe the clinical course of keratoconus and to describe the relationships among its visual and physiological manifestations, including high- and low-contrast visual acuity, corneal curvature, slit lamp biomicroscopic findings, corneal scarring, and quality of life.

To identify risk factors and protective factors that influence the severity and progression of keratoconus.

Condition or disease

Detailed Description:

Keratoconus is a bilateral, asymmetric, chronic, progressive ectasia of the cornea characterized by steepening and distortion of the cornea, thinning of the apical cornea, corneal scarring, and treatment-related sequelae, such as abrasions from contact lenses and surgical complications. Patients experience distorted vision that worsens with disease progression. Their vision is typically corrected with spectacles early in the disease and, later, with rigid contact lenses. Some patients eventually undergo corneal transplantation in one or both eyes. Keratoconus affects people in their prime earning years and profoundly affects their lives.

Previous large-scale studies of keratoconus have focused on incidence and prevalence, etiologies, or the clinical management of keratoconus. Few have characterized the course of the disease and risk factors for its progression in large samples of keratoconus patients. The incidence of vision-threatening corneal scarring in keratoconus is unknown. Patient's most frequent questions--how rapidly their keratoconus will progress, how bad their vision will become, whether they will need corneal surgery, how successful their contact lenses will be--cannot be answered on the basis of the current body of knowledge.

The need for a prospective, observational study of keratoconus patients is great. Results from this study will address keratoconus patient's unanswered questions and will enable eye care practitioners to manage this complex ocular disease better.

The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a multicenter, observational study of 1,209 keratoconus patients followed for 3 years.

Patients are examined annually. Study measures include visual acuity, patient-reported quality of life, manifest refraction, keratometry, photodocumentation of the cornea to identify central corneal scarring, photodocumentation of the flattest contact lens that just clears the cornea, slit lamp biomicroscopy, and corneal topography. In rigid contact lens wearers, the fluorescein pattern of the patient's habitual contact lenses is photodocumented.

Patients are examined at 15 clinical centers. The clinical centers enrolled 1,209 patients in 12 months.

Study Type : Observational
Time Perspective: Prospective
Study Start Date : June 1995

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Information from the National Library of Medicine

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Ages Eligible for Study:   12 Years and older   (Child, Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Patients with keratoconus were eligible if they were at least 12 years old; had an irregular cornea as determined by keratometry, retinoscopy, or direct ophthalmoscopy in at least one eye; had Vogt's striae, Fleischer's ring, or corneal scarring characteristic of keratoconus in at least one eye; and planned to stay in the area for at least 3 years. They were ineligible if they had bilateral corneal transplants or bilateral nonkeratoconic eye disease (cataract, intraocular lenses, macular disease, or optic nerve disease other than glaucoma).

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00000155

United States, California
University of California, Berkeley, School of Optometry
Berkeley, California, United States, 94720-2020
Southern California College of Optometry
Fullerton, California, United States, 92831
Jules Stein Eye Institute, University of California at Los Angeles
Los Angeles, California, United States, 90095-7003
United States, Florida
Nova Southeastern University, Health Professions Division, College of Optometry
Ft. Lauderdale, Florida, United States, 33328
United States, Illinois
University of Illinois at Chicago, Department of Ophthalmology and Visual Sciences
Chicago, Illinois, United States, 60612
United States, Indiana
Indiana University, School of Optometry
Bloomington, Indiana, United States, 47405-3680
United States, Missouri
University of Missouri-St. Louis, School of Optometry
St. Louis, Missouri, United States, 63121
United States, New York
SUNY State College of Optometry
New York, New York, United States, 10036-8003
United States, Ohio
University Hospitals of Cleveland, Department of Ophthalmology
Cleveland, Ohio, United States, 44106
The Ohio State University, College of Optometry
Columbus, Ohio, United States, 43210-1240
United States, Pennsylvania
Pennsylvania College of Optometry, The Eye Institute
Philadelphia, Pennsylvania, United States, 19141
Northeastern Eye Institute
Scranton, Pennsylvania, United States, 18503
United States, Utah
University of Utah, John Moran Eye Center
Salt Lake City, Utah, United States, 84132
United States, Wisconsin
Gundersen Lutheran
La Crosse, Wisconsin, United States, 54601
Sponsors and Collaborators
National Eye Institute (NEI)