title: Higher-order wavefront aberrations in corneal refractive therapy.
abstract: OBJECTIVE
  To assess the changes in higher-order (third through sixth) ocular wavefront aberrations produced by Corneal Refractive Therapy (CRT; Paragon Vision Sciences, Mesa, AZ).
  
  
  METHODS
  Eighteen eyes of nine myopic subjects were fit with CRT contact lenses. Baseline subjective spherical refraction ranged from -2.25 to -6.00 D (mean +/- SD, -3.33 +/- 1.26 D), and baseline logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity was -0.13 +/- 0.06 (20/15 Snellen equivalent). Whole-eye ocular wavefront aberrations were measured using a previously validated Shack-Hartmann aberrometer. Measurements were taken at baseline and 1 month after treatment initiation. Nine measurements per dilated subject were taken and averaged. Zernike coefficients were used to calculate the third-, fourth-, fifth-, and sixth-order root-mean-square values for each eye for both 3- and 6-mm pupil sizes, and aberrations were averaged and compared with prior baseline readings.
  
  
  RESULTS
  The mean (+/-SD) myopia reduction was 3.08 +/- 0.93 D, resulting in a subjective refraction of -0.22 +/- 0.38 D after 1 month of lens wear. Both logMAR uncorrected visual acuity (-0.07 +/- 0.18; 20/15- Snellen equivalent) and best-corrected visual acuity (-0.14 +/- 0.09) after CRT wear were not significantly different from baseline logMAR best-corrected visual acuity (paired two-tailed t-test; p = 0.41 and 0.65, respectively). Whole-eye aberrations showed a statistically significant increase in higher-order aberrations for both 3-mm (factor of 2.66; p = 0.01) and 6-mm pupils (factor of 2.50; p = 0.005). Each individual higher-order aberration also increased, ranging from a factor of 2.01 to 3.20 for 3-mm pupil sizes and 2.52 to 2.98 for 6-mm pupil sizes. Spherical-like aberrations (S4 and S6) increased by a factor of 1.79 for 3-mm pupil sizes and 2.42 for 6-mm pupil sizes. The Zernike coefficient most affected by CRT was spherical aberration (Z40), which increased from 0.084 +/- 0.16 to 0.39 +/- 0.16 microm (p = 0.0002) for 6-mm pupils.
  
  
  CONCLUSIONS
  Use of current CRT lenses for the reduction of myopia increased higher-order wavefront aberrations and spherical aberration (Z40) in particular.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Suite 3.164, Chicago, IL 60612, USA. charjosl@uic.edu
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Joslin
authors.forename: Shelley M
authors.initials: SM
authors.lastname: Wu
authors.forename: Timothy T
authors.initials: TT
authors.lastname: McMahon
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Shahidi
mesh_terms: D000328:Adult; D003261:Contact Lenses / Q000009:adverse effects*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000628:therapy*; D016896:Treatment Outcome; D014786:Vision Disorders / Q000209:etiology*; D014792:Visual Acuity