The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) is an 8-year observational study of 1,209 patients enrolled in the 16 CLEK clinics in the United States during 1994 and 1995. It's the first multicenter clinical study centered in optometry to be funded by the National Eye Institute, a division of the National Institutes of Health. Here, I'll tell you about the highlights.

Principal findings

Here are the principal findings you should know about:

�         The first definite apical clearance lens from the CLEK trial set is more repeatable, especially in more advanced keratoconus, than is keratometry. The CLEK trial lens set is an 8.6- mm diameter, 6.5-mm optic zone, 8.5-mm secondary curve, 11-mm/0.2-mm wide peripheral curve, polymethylmethacrylate trial set.

�         The mean age of the CLEK patients was 39 at baseline. At baseline, 65% wore rigid gas permeable (RGP) lenses, 13.5% reported a family history of keratoconus, 53% reported a history of atopy and none reported serious systemic disease associated with keratoconus.

�         Even if they don't wear contact lenses, keratoconus patients have more pain in and around their eyes than normal patients who wear RGP lenses.

�         Nearly 78% of patients had at least 20/40 best corrected visual acuity with both eyes at baseline. Although cause and effect can't be proven in this study, patients with corneal scarring were more likely to have worn any type of contact lens and three to four times more likely to have had corneal staining.

�         Keratoconus patients are highly likely to have reduced low contrast visual acuity (usually not measured clinically). This is even more likely when a corneal scar exists.

�         Keratoconus patients who are randomly fitted into piggy-back lenses are likely to be comfortable and have good vision and acceptable corneal tissue changes, but are more likely than RGP-only wearers to drop out of this fitting modality. Nevertheless, 7 of 10 patients may accept this method of treatment.

The CLEK study will be completed in 2004.

Dr. Barr's practice

Our contact lens clinic is located on The Ohio State University campus in the College of Optometry in Columbus, Ohio. Columbus is a very white-collar city of about 1 million people. About 50,000 students attend Ohio State. Thus, it's a target-rich environment for contact lens patients.

I've practiced here since 1977, but the contact lens clinic has been here since about 1950. We fit more than 150 patients per week in this clinic, and about one-third that amount at the student health center in the central campus.

We have about 15 staff to cover all of our primary care, contact lens, binocular vision, pediatric, low vision and aniseikonia clinics. One staff person performs almost all of the contact lens work. About 18% of our revenue comes from contact lenses; about 20% of the patients are contact lens patients. A higher number than in most clinics are keratoconus and post-surgical (or referral) patients.

I estimate that 25% wear RGPs; 40% wear soft disposable spheres; 15% wear planned-replacement spheres; 15% wear soft torics; 3% wear conventional wear and 2% wear cosmetic tints. We use both direct-from-manufacturer and through-the-clinic lens delivery. We see daily wear patients at least once per year, and extended wear patients at least every 6 months.

Dr. Barr is a professor and assistant dean for clinical affairs at the Ohio State University College of Optometry in Columbus, Ohio.

Leading People

Though more than 100 people contribute to the CLEK Study, the following are key:

�         Karla Zadnik, O.D., Ph.D., study chairman, The Ohio State University, Columbus, Ohio

�         Joe Barr, O.D., M.S., chairman, CLEK Photography Reading Center, The Ohio State University College of Optometry, Columbus, Ohio

�         Timothy B. Edrington, O.D., M.S., principal investigator at Southern California College of Optometry, Executive Committee Member, Fullerton, Calif.

�         Timothy T. McMahon, O.D., director, CLEK Topography Reading Center, University of Illinois, Chicago, and PI of the University of Illinois, Chicago CLEK Clinic

�         Mae O. Gordon, Ph.D., director, CLEK Coordinating Center, Washington University, St. Louis

�         Donald F. Everett, M.A., project officer, NEI, Bethesda, Md.

�         W. Joseph "Joe" Benjamin, O.D., prin. inv., University of Alabama at Birmingham, Birmingham, Ala.

�         Loretta Szczotka, O.D., M.S., prin. inv., University Hospitals of Cleveland, Case Western Reserve University, Ohio

�         John L. Sterling, O.D., prin. inv., Gunderson Lutheran, LaCrosse, Wis.

�         Gerald E. Lowther, O.D., Ph.D., prin. inv., Indiana University, Bloomington, Ind.

�         Barry A. Weissman, O.D., Ph.D., prin. inv., Jules Stein Eye Inst. UCLA, Los Angeles

�         Larry Davis, O.D., prin. inv., University of Missouri, St. Louis

�         Joseph P. Shovlin, O.D., prin. inv., Northeastern Eye Institute, Scranton, Pa.

�         Heidi Wagner, O.D., prin. inv., NOVA Southeastern University, Ft. Lauderdale, Fla.

�         Barbara A. Fink, O.D., Ph.D., prin. inv., The Ohio State University, Columbus, Ohio

�         Joel A. Silbert, O.D., prin. inv., Pennsylvania College of Optometry, Philadelphia

�         David P. Libassi, O.D., prin. inv., State University of New York College of Optometry, New York

�         Harald E. Olafsson, O.D., prin. inv., University of Utah, Salt Lake City