title: Time course of dichoptic masking in normals and suppression in amblyopes.
abstract: OBJECTIVE
  To better understand the relationship between dichoptic masking in normal vision and suppression in amblyopia we address three questions: First, what is the time course of dichoptic masking in normals and amblyopes? Second, is interocular suppression low-pass or band-pass in its spatial dependence? And third, in the above two regards, is dichoptic masking in normals different from amblyopic suppression?
  
  
  METHODS
  We measured the dependence of dichoptic masking in normal controls and amblyopes on the temporal duration of presentation under three conditions; monocular (the nontested eye-i.e., dominant eye of normals or nonamblyopic eye of amblyopes, being patched), dichoptic-luminance (the nontested eye seeing a mean luminance-i.e., a DC component) and dichoptic-contrast (the nontested eye seeing high-contrast visual noise). The subject had to detect a letter in the other eye, the contrast of which was varied.
  
  
  RESULTS
  We found that threshold elevation relative to the patched condition occurred in both normals and amblyopes when the nontested eye saw either 1/f or band-pass filtered noise, but not just mean luminance (i.e., there was no masking from the DC component that corresponds to a channel responsive to a spatial frequency of 0 cyc/deg); longer presentation of the target (corresponding to lower temporal frequencies) produced greater threshold elevation.
  
  
  CONCLUSIONS
  Dichoptic masking exhibits similar properties in both subject groups, being low-pass temporally and band-pass spatially, so that masking was greatest at the longest presentation durations and was not greatly affected by mean luminance in the nontested eye.
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Zhou
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada School of Optometry, University of Waterloo, Ontario, Canada.
authors.forename: Suzanne
authors.initials: S
authors.lastname: McNeal
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada School of Optometry, University of Waterloo, Ontario, Canada.
authors.forename: Raiju J
authors.initials: RJ
authors.lastname: Babu
authors.affiliation: Department of Psychology, University of York, York, United Kingdom.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Baker
authors.affiliation: School of Optometry, University of Waterloo, Ontario, Canada.
authors.forename: William R
authors.initials: WR
authors.lastname: Bobier
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Province of Quebec, Canada.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Hess
mesh_terms: D000328:Adult; D000550:Amblyopia / Q000503:physiopathology*; D015350:Contrast Sensitivity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation; D012684:Sensory Thresholds; D013997:Time Factors; D015348:Vision, Binocular / Q000502:physiology*; D055815:Young Adult
keywords: amblyopia; dichoptic masking; presentation duration; spatial; suppression; temporal