title: Pilot study: effect of age on visual acuity with defocus and astigmatism.
abstract: OBJECTIVE
  To investigate how distance visual acuity in the presence of defocus and astigmatism is affected by age and whether aberration properties of young and older eyes can explain any differences.
  
  
  METHODS
  Participants were 12 young adults (mean [±SD] age, 23 [±2] years) and 10 older adults (mean [±SD] age, 57 [±4] years). Cyclopleged right eyes were used with 4-mm effective pupil sizes. Thirteen blur conditions were used by adding five spherical lens conditions (-1.00 diopters [D], -0.50 D, plano/0.00 D, +0.50 D, and +1.00 D) and adding two cross-cylindrical lenses (+0.50 DS/-1.00 DC and +1.00 D/-2.00 DC, or 0.50 D and 1.00 D astigmatism) at four negative cylinder axes (45, 90, 135, and 180 degrees). Targets were single lines of high-contrast letters based on the Bailey-Lovie chart. Successively smaller lines were read until a participant could no longer read any of the letters correctly. Aberrations were measured with a COAS-HD Hartmann-Shack aberrometer.
  
  
  RESULTS
  There were no significant differences between the two age groups. We estimated that 70 to 80 participants per group would be needed to show significant effects of the trend of greater visual acuity loss for the young group. Visual acuity loss for astigmatism was twice that for defocus of the same magnitude of blur strength (0.33 logMAR [logarithm of the minimum angle of resolution]/D compared with 0.18 logMAR/D), contrary to the geometric prediction of similar loss.
  
  
  CONCLUSIONS
  Any age-related differences in visual acuity in the presence of defocus and astigmatism were swamped by interparticipant variation.
authors.affiliation: *PhD, FAAO †PhD ‡DSc, FAAO School of Optometry & Vision Science and Institute of Health & Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland, Australia (all authors).
authors.forename: Ankit
authors.initials: A
authors.lastname: Mathur
authors.forename: Marwan
authors.initials: M
authors.lastname: Suheimat
authors.forename: David A
authors.initials: DA
authors.lastname: Atchison
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001251:Astigmatism / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology*; D008297:Male; D009216:Myopia / Q000503:physiopathology*; D010865:Pilot Projects; D014786:Vision Disorders / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult