TY - JOUR
T1 - Repeatability of refraction and corrected visual acuity in keratoconus
AU - Davis, Larry J.
AU - Schechtman, Kenneth B.
AU - Begley, Carolyn G.
AU - Shin, Julie A.
AU - Zadnik, Karla
PY - 1998/12
Y1 - 1998/12
N2 - Purpose. The purpose of the test-retest phase of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study was to determine the repeatability of the various parts of the CLEK Study protocol. This paper presents the test-retest parameters of the refraction protocol. Methods. We examined 138 CLEK Study-eligible patients on two occasions (median, 90 days; range, 22 to 268 days). All patients underwent subjective refraction on two occasions, and contact lens over-refractions were performed either over the patient's habitual rigid contact lenses or over a trial rigid contact lens equal in base curve to the steep keratometric reading in nonrigid contact lens wearers. Results. Mean interoccasion differences ± SD were -0.32 ± 2.91 D and -0.17 ± 1.39 D for subjective refraction sphere and cylinder power, respectively, and the mean absolute difference for subjective refraction cylinder axis was 18.1 ± 20.2°. The mean interoccasion difference ± SD for high-contrast visual acuity with subjective refraction was 0.38 ± 10.9 letters correct. Mean interoccasion differences ± SD were - 0.11 ± 0.81 D and 0.02 ± 0.67 D for contact lens over-refraction sphere and cylinder power, respectively, and the mean absolute differences for contact lens over-refraction cylinder axis was 11.6 ± 9.9°. The mean interoccasion difference ± SD for visual acuity with contact lens over-refraction was 0.50 ± 5.2 letters correct and 0.71 ± 6.9 letters correct for high- and low- contrast visual acuity, respectively. Conclusions. The repeatability of subjective refraction in keratoconus patients is good but somewhat lower than that found in nondiseased eyes. Only 36% of our repeat measures of sphere power from subjective refraction fell within 0.50 D of each other, compared with more than 90% in studies of normal eyes.
AB - Purpose. The purpose of the test-retest phase of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study was to determine the repeatability of the various parts of the CLEK Study protocol. This paper presents the test-retest parameters of the refraction protocol. Methods. We examined 138 CLEK Study-eligible patients on two occasions (median, 90 days; range, 22 to 268 days). All patients underwent subjective refraction on two occasions, and contact lens over-refractions were performed either over the patient's habitual rigid contact lenses or over a trial rigid contact lens equal in base curve to the steep keratometric reading in nonrigid contact lens wearers. Results. Mean interoccasion differences ± SD were -0.32 ± 2.91 D and -0.17 ± 1.39 D for subjective refraction sphere and cylinder power, respectively, and the mean absolute difference for subjective refraction cylinder axis was 18.1 ± 20.2°. The mean interoccasion difference ± SD for high-contrast visual acuity with subjective refraction was 0.38 ± 10.9 letters correct. Mean interoccasion differences ± SD were - 0.11 ± 0.81 D and 0.02 ± 0.67 D for contact lens over-refraction sphere and cylinder power, respectively, and the mean absolute differences for contact lens over-refraction cylinder axis was 11.6 ± 9.9°. The mean interoccasion difference ± SD for visual acuity with contact lens over-refraction was 0.50 ± 5.2 letters correct and 0.71 ± 6.9 letters correct for high- and low- contrast visual acuity, respectively. Conclusions. The repeatability of subjective refraction in keratoconus patients is good but somewhat lower than that found in nondiseased eyes. Only 36% of our repeat measures of sphere power from subjective refraction fell within 0.50 D of each other, compared with more than 90% in studies of normal eyes.
KW - Keratoconus
KW - Refraction
KW - Repeatability
KW - Subjective refraction
UR - http://www.scopus.com/inward/record.url?scp=0032437683&partnerID=8YFLogxK
U2 - 10.1097/00006324-199812000-00011
DO - 10.1097/00006324-199812000-00011
M3 - Article
C2 - 9875994
AN - SCOPUS:0032437683
SN - 1040-5488
VL - 75
SP - 887
EP - 896
JO - Optometry and Vision Science
JF - Optometry and Vision Science
IS - 12
ER -