title: Accommodative Gain in Relation to Perceived Target Clarity.
abstract: OBJECTIVE
  The purpose of this study is to determine the relationship between target clarity and the magnitude of accommodative lag using the metric accommodative gain (AG).
  
  
  METHODS
  Monocular accommodative responses were measured with Grand Seiko autorefraction using both proximal and minus lens techniques in 139 subjects aged 5 to 35 years. Subjects viewed a 1.5-mm letter at 13 discrete distances (range, 40 to 3.33 cm) for the proximal technique and fixed at 33 cm through minus lenses of increasing power for the lens technique. Subjects were instructed to keep the target clear and report when it blurred. The AG was calculated (accommodative response/accommodative demand) for the four greatest consecutive demands perceived clear (termed conditions 1 to 4) and the first demand perceived blurry (termed condition 5).
  
  
  RESULTS
  Multivariate planned contrast, including age as a predictor, revealed that mean AG was significantly larger when the target was clear (range, 0.71 to 0.77 for conditions 1 to 4 across techniques) versus blurry (0.59 and 0.68 for condition 5 across techniques) (p < 0.001 for proximal and p < 0.036 for lens). Age was only a contributing factor for the proximal technique, with the youngest subjects having the largest decrease in AG when the target changed from clear to blurry (p = 0.017).
  
  
  CONCLUSIONS
  These data suggest that across age and technique, the AG is relatively constant when the target is perceived clear but drops below approximately 70%, on average, once the target is perceived as blurry for subjects aged 5 to 35 years. The AG may be a useful metric to compare accommodative responses across a range of demands and to identify accommodative responses that may not be sufficient to perceive a clear target.
authors.affiliation: *OD, MS, FAAO †OD, PhD, FAAO ‡PhD College of Optometry (TLR, HAA) and Houston Department of Psychology/TIMES Institute (KKS), University of Houston, Houston, Texas.
authors.forename: Tawna L
authors.initials: TL
authors.lastname: Roberts
authors.forename: Heather A
authors.initials: HA
authors.lastname: Anderson
authors.forename: Karla K
authors.initials: KK
authors.lastname: Stuebing
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D015350:Contrast Sensitivity / Q000502:physiology*; D005139:Eyeglasses; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D015348:Vision, Binocular / Q000502:physiology; D055815:Young Adult