title: Repeatability of peripheral aberrations in young emmetropes.
abstract: OBJECTIVE
  The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported.
  
  
  METHODS
  The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10° out to ±40° in the horizontal visual field (nasal + and temporal -) and -20° in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability.
  
  
  RESULTS
  In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was <30% and the intraclass correlation coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C(3)(1)) was most positive at 40° in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change.
  
  
  CONCLUSIONS
  The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field.
authors.affiliation: Vision Enabling Laboratory, Unit of Optometry and Vision Science, School of Natural Sciences, Linnaeus University, Kalmar, Sweden.
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Baskaran
authors.forename: Baskar
authors.initials: B
authors.lastname: Theagarayan
authors.forename: Staffan
authors.initials: S
authors.lastname: Carius
authors.forename: Jörgen
authors.initials: J
authors.lastname: Gustafsson
mesh_terms: D057128:Aberrometry / Q000295:instrumentation / Q000706:statistics & numerical data*; D058453:Emmetropia / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000175:diagnosis; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult