title: Stereoacuity as an indicator of prism adaptation.
abstract: OBJECTIVE
  The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation.
  
  
  METHODS
  Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively. Prism vergences were measured using a prism bar. For each participant, prism power equivalent to the blur point of base-in (BI) and base-out (BO) fusional vergence at 40 cm was divided and placed in front of both eyes. At 0, 3, 6, 9 and 12 min after prism introduction, the stereoacuity was measured, and at 0 and 12 min, the heterophoria was measured.
  
  
  RESULTS
  The repeated measures ANOVA showed a significant difference between the mean stereoacuity for BI and BO prisms at the different measurement times (p < 0.05). For BO prism, the initial value was different between 0 and 3 min after the prism introduction, whereas for BI prism, a difference in stereoacuity was found between the pre-prism value and the value at 0, 3 and 6 min. The size of the heterophoria with BO and BI prisms was different from 0 to 12 min (p < 0.05).
  
  
  CONCLUSIONS
  The time required for stereoacuity to return to baseline level was more than 3 min for BO, and more than 6 min for BI prism. In addition, the time required to return to baseline values was not similar for the stereoacuity and heterophoria. The recovery of stereoacuity is slower when adapting to divergence, as when looking from near to far. This implies that stereopsis responds faster to near targets than to distant one, and may precede complete phoria adaptation.
authors.affiliation: Health Promotion Research Center, Zahedan University of Medical Sciences , Zahedan , Iran .
authors.forename: Hamed
authors.initials: H
authors.lastname: Momeni-Moghaddam
authors.forename: Frank
authors.initials: F
authors.lastname: Eperjesi
authors.forename: James
authors.initials: J
authors.lastname: Kundart
authors.forename: Kazem
authors.initials: K
authors.lastname: Mostafavi-Nam
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D013285:Strabismus / Q000503:physiopathology* / Q000628:therapy; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity; D055815:Young Adult
keywords: Binocular alignment; binocular vision; prism adaptation; stereopsis; vergence adaptation