title: Near stereothresholds measured with random-dot stereograms using phase disparities.
abstract: BACKGROUND
  Clinically, stereothresholds for random-dot (RD) stimuli are measured at near with a typical resolution of 20- to 40-seconds arc. In this article, we describe a method by which stereothresholds are measured using RD stimuli on a conventional computer monitor with sub-picture-element spatial resolution.
  
  
  METHODS
  The RD stimuli consisted of individual left and right eye images, viewed haploscopically from 50 cm though orthogonal polarizers. Cross and uncrossed horizontal disparities as small as 6-seconds arc were produced by introducing appropriate phase disparities within the individual spatial frequency components of the RD stimulus. The method of constant stimuli was used to determine the stereothresholds for 20 normal adult observers.
  
  
  RESULTS
  The mean stereothreshold across the 20 observers was 24.1 +/- 16.6-seconds arc, with an average trial-to-trial variability of +/- 23%.
  
  
  CONCLUSIONS
  Stereothresholds of a few-second arc can be measured accurately from a near distance for RD stimuli, using a conventional computer monitor. A clinical test based on this technique would allow the measurement of global stereothresholds with very high spatial resolution.
authors.affiliation: College of Engineering, University of Houston, Texas 77204-2020, USA.
authors.forename: Saumil S
authors.initials: SS
authors.lastname: Patel
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ukwade
authors.forename: Harold E
authors.initials: HE
authors.lastname: Bedell
authors.forename: Vanitha
authors.initials: V
authors.lastname: Sampath
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003196:Computer Graphics; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time; D012684:Sensory Thresholds / Q000502:physiology*