OM t of c.iii - Vision Research Coordinating Center - Washington ...

2/1/99 Chapter 2 Study Design page 2-1
2.1 CLEK Study Summary
Chapter 2
Study Design, Timetable and Rationale
Keratoconus is a visually disabling thinning disorder of the central cornea that
results in irregular astigmatism, progressive corneal distortion, and corneal scarring
(Krachmer et al., 1984). The astigmatism and distortion are usually treated with rigid
contact lenses. When severe scarring occurs, or when the visual distortion is beyond
optical correction, in 10 to 20% of patients, the cornea is repaired or replaced by surgery
(Kennedy et al., 1986).
The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a
multi-center, observational study designed to describe the course of this chronic ocular
disease and to determine the associations among its visual and physiological
manifestations. One thousand keratoconus patients are enrolled at 16 Participating
Clinics over the course of ten months. Each is examined at baseline and annually for at
least three years. Examinations include visual acuity, manifest refraction, patientreported
quality of life, keratometry, photodocumentation of the cornea to identify
central corneal scarring, and slit lamp biomicroscopy. In rigid contact lens wearers, the
fluorescein pattern of the patient’s lenses is documented. The flattest CLEK Study trial
lens that demonstrates an apical clearance fluorescein pattern is photodocumented in all
patients.
The CLEK Study characterizes keratoconus over the course of the disease both by
initially enrolling patients at various diseases stages and by following all those patients
for three years. The goal is to characterize the disease across its course and to identify
risk factors and protective factors that determine the severity and progression of the
disease.
2.1.1 CLEK Study Timetable
Each Clinic is expected to enroll at least 80 patients in a 10-month period, and
patients are followed annually for nine years for a total of eight visits. Participating
Clinics are reimbursed by the Study Chairman’s office for each CLEK Study patient
visit ($300 for each visit). Patients are reimbursed $20 for each Study Visit. Participating
Clinics and their referring doctors continue to administer all routine eye care, contact
lens care, and surgical care to CLEK Study patients on their usual fee-for-service basis.