Clinical trial NCT00000155: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study
Study type: OBSERVATIONAL
Overall status: UNKNOWN
Conditions: Keratoconus
Lead sponsor: National Eye Institute (NEI)
Sponsor class: NIH
First posted: 1999-09-24
Sex: ALL
Minimum age (years): 12
Standard ages: CHILD
ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Time perspective: PROSPECTIVE

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.

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.

Eligibility criteria: 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).

Primary outcomes:
Secondary outcomes:
Other outcomes:
Locations:
city: Berkeley
country: United States
facility: University of California, Berkeley, School of Optometry
state: California
city: Fullerton
country: United States
facility: Southern California College of Optometry
state: California
city: Los Angeles
country: United States
facility: Jules Stein Eye Institute, University of California at Los Angeles
state: California
city: Ft. Lauderdale
country: United States
facility: Nova Southeastern University, Health Professions Division, College of Optometry
state: Florida
city: Chicago
country: United States
facility: University of Illinois at Chicago, Department of Ophthalmology and Visual Sciences
state: Illinois
city: Bloomington
country: United States
facility: Indiana University, School of Optometry
state: Indiana
city: St. Louis
country: United States
facility: University of Missouri-St. Louis, School of Optometry
state: Missouri
city: New York
country: United States
facility: SUNY State College of Optometry
state: New York
city: Cleveland
country: United States
facility: University Hospitals of Cleveland, Department of Ophthalmology
state: Ohio
city: Columbus
country: United States
facility: The Ohio State University, College of Optometry
state: Ohio
city: Philadelphia
country: United States
facility: Pennsylvania College of Optometry, The Eye Institute
state: Pennsylvania
city: Scranton
country: United States
facility: Northeastern Eye Institute
state: Pennsylvania
city: Salt Lake City
country: United States
facility: University of Utah, John Moran Eye Center
state: Utah
city: La Crosse
country: United States
facility: Gundersen Lutheran
state: Wisconsin
Study officials:
References:
citation: 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 May-Jun;12(4):492-500. doi: 10.3928/1081-597X-19960501-13.
citation: Edrington TB, Barr JT, Zadnik K, Davis LJ, Gundel RE, Libassi DP, McMahon TT, Gordon MO. Standardized rigid contact lens fitting protocol for keratoconus. Optom Vis Sci. 1996 Jun;73(6):369-75. doi: 10.1097/00006324-199606000-00003.
citation: Gundel RE, Libassi DP, Zadnik K, Barr JT, Davis L, McMahon TT, Edrington TB, Gordon MO. Feasibility of fitting contact lenses with apical clearance in keratoconus. Optom Vis Sci. 1996 Dec;73(12):729-32. doi: 10.1097/00006324-199612000-00002.
citation: Zadnik K, Barr JT, Gordon MO, Edrington TB. Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. Cornea. 1996 Mar;15(2):139-46. doi: 10.1097/00003226-199603000-00006.