title: Effect of target distance on accommodative amplitude measured using the minus lens technique.
abstract: BACKGROUND
  The aim was to investigate the effect on the measured amplitude of accommodation and repeatability of using the minus lens technique with the target at distance or near.
  
  
  METHODS
  Forty-three students (average age: 21.17 ± 1.50 years, 35 female) had their amplitude of accommodation measured with minus lenses on top of their distance correction in a trial frame with the target at far (6.0 m) or near (0.4 m). The minus lens power was gradually added with steps of 0.25 D. Measurements were taken on two occasions at each distance, which were separated by a time interval of at least 24 hours.
  
  
  RESULTS
  The measured amplitude at six metres was significantly lower than that with the target at 40 cm, by 1.56 ± 1.17 D (p < 0.001) and this varied between individuals (r = 0.716, intraclass correlation coefficient = 0.439). With either target distance, repeated measurement was highly correlated (r > 0.9) but the agreement was better at 6.0 m (±0.74 D) than at 40 cm (± 0.92 D).
  
  
  CONCLUSIONS
  The measurements of the amplitude of accommodation with the minus lens technique using targets at far or near are not comparable and the difference between the target distances may provide clinically relevant information.
authors.affiliation: Health Promotion Research Center, Zahedan University of Medical Sciences, Zahedan, Iran. hmomeni_opt@yahoo.com.
authors.forename: Hamed
authors.initials: H
authors.lastname: Momeni-Moghaddam
authors.forename: James S
authors.initials: JS
authors.lastname: Wolffsohn
authors.forename: Abbas
authors.initials: A
authors.lastname: Azimi
authors.forename: Elnaz
authors.initials: E
authors.lastname: Babaei-Malekkolaei
mesh_terms: D000065:Accommodation, Ocular; D000293:Adolescent; D005260:Female; D006801:Humans; D008297:Male; D009907:Optometry / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D012030:Refractive Errors / Q000175:diagnosis*; D015203:Reproducibility of Results; D042262:Retinoscopy / Q000379:methods* / Q000592:standards*; D055815:Young Adult
keywords: accommodation amplitude; agreement; minus lens method; repeatability