Biomedical subjects

Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group

Publications and source records attributed to Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.

3 recordsLinked to original sources

PubMed2006

Longitudinal changes in visual acuity in keratoconus.

PURPOSE: The present investigation aimed to identify factors that predict reduced visual acuity in keratoconus from a prospective, longitudinal study. METHODS: This report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study used 7 years of follow-up data from 953 CLEK subjects who did not have penetrating keratoplasty in either eye at baseline and who provided enough data to compute the slope of the change over time in high- or low-contrast best-corrected visual acuity (BCVA). Outcome measures included these slopes and whether the number of letters correctly read decreased by 10 letters or more in at least one eye in 7 years. RESULTS: Mean age of the subjects at the first follow-up visit was 40.2 +/- 11.0 years (mean +/- SD). Overall, 44.4% were female, and 71.9% were white. The slope of the change in high- and low-contrast BCVA (-0.29 +/- 1.5 and -0.58 +/- 1.7 letters correct/year, respectively) translated into expected 7-year decreases of 2.03 high- and 4.06 low-contrast letters correct. High- and low-contrast visual acuity decreases of 10 or more letters correct occurred in 19.0% and 30.8% of subjects, respectively. Independent predictors of reduced high- and low-contrast BCVA included better baseline acuity, steeper first definite apical clearance lens (FDACL), and fundus abnormalities. Each diopter of steeper baseline FDACL predicted an increased deterioration of 0.49 high- and 0.63 low-contrast letters correct. CONCLUSIONS: CLEK Study subjects with keratoconus exhibited a slow but clear decrease in BCVA during follow-up, with low-contrast acuity deteriorating more rapidly than high-contrast. Better baseline BCVA, steeper FDACL, and fundus abnormalities were predictive of greater acuity loss with time.

Adult↗

PubMed2005

Comparison of flat and steep rigid contact lens fitting methods in keratoconus.

PURPOSE: The purpose of this article is to compare the safety and efficacy of flat- and steep-fitting rigid contact lenses in keratoconus. METHODS: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a 16-center observational study. Cross-sectional results at baseline were generated for 1091 subjects with longitudinal results from the 871 subjects who completed 8 years of follow up. RESULTS: Of the 761 rigid contact lens-wearing patients at baseline, 41% had a scar at baseline compared with 24% of the nonrigid contact lens wearers (odds ratio [OR], 2.15; 95% confidence interval [CI], 1.35-3.43; p = 0.001). Eighty-seven percent were fitted with flat-fitting lenses, whereas 13% were fitted with steep-fitting lenses. Rigid lens fitting method was also associated with incident corneal scarring. A greater proportion of the corneas wearing flat-fitting contact lenses were scarred (43% compared with 26% for the steep-fitted eyes; OR,= 2.19; 95% CI, 1.37-3.51; p = 0.001). After controlling for corneal curvature, the association of rigid contact lens fit and corneal scarring at baseline did not persist (adjusted OR, 1.20; 95% CI, 0.70-2.06; p = 0.52). Thirty-two percent of unscarred eyes at baseline fitted flat had developed an incident corneal scar by the eighth year follow-up visit compared with 14% of eyes fitted steep (OR, 2.93; 95% CI, 1.34-6.42; p = 0.007). CONCLUSIONS: The data reported here indicate that, after controlling for disease severity in the form of corneal curvature, keratoconic eyes fitted with a rigid contact lens resulting in an apical touch fluorescein pattern did not have an increased risk of being scarred centrally at baseline. This "natural history" sample cannot determine causal proof that one method of fitting lenses is safer than another. To achieve this, a randomized clinical trial is needed.

Contact Lenses↗

PubMed2002

Lysosomal hydrolase staining of conjunctival impression cytology specimens in keratoconus.

PURPOSE: This study sought to assess the feasibility of impression cytology for the determination of conjunctival intracellular lysosomal hydrolase (acid esterase) levels in patients with keratoconus. METHODS: Twenty-two patients with keratoconus currently enrolled in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study and 22 age-and sex-similar controls underwent impression cytology. Samples were collected from each subject and control pair on the same day. The cells of the respective specimens were fixed immediately and were stained for acid esterase with use of identical batches of fixatives and stains. After staining, the specimens were cleared in xylene for mounting in synthetic resin on glass slides. The acid esterase staining intensity of each specimen was quantified as the percentage of light transmitted with use of an image analysis system (Zeiss). Multiple cells from each specimen were analyzed for each sample collected. RESULTS: Mixed model analysis was used to account for the subject-control pairings and for the multiple cells from each sample. With this method, the mean light transmission for normal controls (mean = 63.0; standard error [SE] = 3.0) was highly statistically significantly different from that for the keratoconus subjects (mean = 52.4; SE = 3.0) (two-tailed p= 0.0032). CONCLUSIONS: This study establishes the feasibility of adapting an acid esterase staining technique to conjunctival cells collected via impression cytology. Higher levels of lysosomal enzyme staining in patients with keratoconus have been previously reported by other investigators using full-thickness conjunctival specimens. We also demonstrate the value of using objective microspectrophotometry in measuring lysosomal enzyme staining with impression cytology specimens.

Acetylesterase↗