title: Vergence facility with stereoscopic and nonstereoscopic targets.
abstract: OBJECTIVE
  To compare vergence facility with nonstereo and stereo targets in binocular symptomatic and asymptomatic subjects.
  
  
  METHODS
  Sixty-six students were divided into symptomatic and asymptomatic groups according to the Convergence Insufficiency Symptom Survey Questionnaire score. Vergence facility was tested at 40 cm by flipper prism 3Δ BI/12Δ BO (BI, base-in; BO, base-out). The targets used were a nonstereo target (a vertical column of small letter "E" of ~20/30 size), a stereo-local target (fifth set of circles of the Titmus test with stereoacuity of 100 arcsec), and a stereo-global target (page 6 of the TNO test with stereoacuity of 120 arcsec).
  
  
  RESULTS
  Repeated-measures analysis of variance showed differences in the mean vergence facility with different targets in all subjects and separately in two symptom groups (p < 0.001). In all subjects and separately in the symptomatic subjects, this difference was statistically significant among the three different targets (p < 0.05). In the asymptomatic subjects, this difference was not significant between the measured values with nonstereo and stereo-local targets (p > 0.05) but significant for the comparison of stereo-global targets with the other two targets. The receiver operating characteristic curve analysis showed the cutoff points 10.5, 10.5, and 9.75 cycles per minute with nonstereo, stereo-local, and stereo-global targets, respectively. The sensitivity of the three targets used was the same (97%). Specificity was 0.93 or higher with all three targets, with the highest specificity obtained with the stereo-global target (100%).
  
  
  CONCLUSIONS
  The highest vergence facility was obtained with a nonstereo target and the lowest was obtained with a stereo-global target. High sensitivity with all three targets means that there are few false-negative results with them, and the high specificity is indicative of low false-positive results. Hence, the vergence facility predictive value would be high in diagnosing binocular symptomatic patients using a 3Δ BI/12Δ BO prism flipper at near and a response cutoff of about 10 cycles per minute or less.
authors.affiliation: *MSc †OD, PhD ‡BSc Health Promotion Research Center (HM-M) and School of Optometry (AD), Zahedan University of Medical Sciences, Zahedan, Iran; and School of Optometry, Indiana University, Bloomington, Indiana (DAG).
authors.forename: Hamed
authors.initials: H
authors.lastname: Momeni-Moghaddam
authors.forename: David A
authors.initials: DA
authors.lastname: Goss
authors.forename: Abubakr
authors.initials: A
authors.lastname: Dehvari
mesh_terms: D000328:Adult; D003290:Convergence, Ocular / Q000502:physiology*; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012372:ROC Curve; D012029:Refraction, Ocular / Q000502:physiology*; D042262:Retinoscopy; D011795:Surveys and Questionnaires; D015348:Vision, Binocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult