Contrast sensitivity function and ocular higher-order aberrations following overnight orthokeratology
Hiraoka, T.; Okamoto, C.; Ishii, Y.; Kakita, T.; Oshika, T.
IOVS Investigative Ophthalmology and Visual Science 48(2): 550-556
2007
ISSN/ISBN: 0146-0404 PMID: 17251449 DOI: 10.1167/iovs.06-0914
Accession: 012957027
PURPOSE. To evaluate relationships among contrast sensitivity function, ocular higher-order aberration, and myopic correction in eyes undergoing overnight orthokeratology for myopia.METHODS. A prospective study was conducted in 46 eyes of 23 patients undergoing orthokeratology. Inclusion criteria were spherical equivalent refraction between -1.00 and -4.00 diopters ( D), refractive astigmatism up to 1.00 D, and best-corrected visual acuity of 20/20 or better. Ocular higher-order aberrations and contrast sensitivity function were determined before and 3 months after initiation of the procedure. We measured three indices of contrast sensitivity function: contrast sensitivity, low-contrast visual acuity, and letter contrast sensitivity with the CSV-1000 charts ( Vector Vision Co., Greenville, OH). Area under the log contrast sensitivity function ( AULCSF) was calculated from the contrast sensitivity data.RESULTS. Orthokeratology significantly improved logMAR uncorrected visual acuity ( P < 0.0001; paired t-test) but significantly increased ocular higher-order aberrations ( P < 0.0001) and decreased contrast sensitivity function, including AULCSF ( P < 0.0001), low-contrast visual acuity ( P = 0.0025), and letter contrast sensitivity ( P < 0.0001; Wilcoxon signed-rank test). The induced changes in AULCSF, low-contrast visual acuity, and letter contrast sensitivity by orthokeratology showed significant correlation with changes in third-order ( Pearson r = -0.430, P = 0.0026; r = 0.423, P = 0.0031; and Spearman r(s) = -0.351, P = 0.0186, respectively), fourth-order ( r = -0.418, P = 0.0035; r = 0.425, P = 0.0029; and r(s) = -0.566, P = 0.0001, respectively), and total higher-order ( r = -0.460, P = 0.0011; r = 0.471, P = 0.0008; and r(s) = -0.434, P = 0.0036, respectively) aberrations. The induced changes in contrast sensitivity function and higher-order aberrations significantly correlated with the amount of myopic correction ( P < 0.01).CONCLUSIONS. Orthokeratology significantly increases ocular higher-order aberrations and compromises contrast sensitivity function, depending on the amount of myopic correction.