title: Visual suppression in intermittent exotropia during binocular alignment.
abstract: OBJECTIVE
  To investigate the cortical mechanisms that prevent diplopia in intermittent exotropia (X(T)) during binocular alignment (orthotropia).
  
  
  METHODS
  The authors studied 12 X(T) patients aged 5 to 22 years. Seventy-five percent had functional stereo vision with stereoacuity similar to that of 12 age-matched controls (0.2-3.7 min arc). Identical face images were presented to the two eyes for 400 ms. In one eye, the face was presented at the fovea; in the other, offset along the horizontal axis with up to 12° eccentricity. The task was to indicate whether one or two faces were perceived.
  
  
  RESULTS
  All X(T) patients showed normal diplopia when the nonfoveal face was presented to nasal hemiretina, though with a slightly larger fusional range than age-matched controls. However, 10 of 12 patients never experienced diplopia when the nonfoveal face was presented to temporal hemiretina (i.e., when the stimulus simulated exodeviation). Patients showed considerable variability when the single image was perceived. Some patients suppressed the temporal stimulus regardless of which eye viewed it, whereas others suppressed a particular eye even when it viewed the foveal stimulus. In two patients, the simulated exodeviation might have triggered a shift from normal to anomalous retinal correspondence.
  
  
  CONCLUSIONS
  Antidiplopic mechanisms in X(T) can be reliably triggered by purely retinal information during orthotropia, but the nature of these mechanisms varies between patients.
authors.affiliation: Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom. i.s.pedraza@ncl.ac.uk
authors.forename: Ignacio
authors.initials: I
authors.lastname: Serrano-Pedraza
authors.forename: Vina
authors.initials: V
authors.lastname: Manjunath
authors.forename: Olaoluwakitan
authors.initials: O
authors.lastname: Osunkunle
authors.forename: Michael P
authors.initials: MP
authors.lastname: Clarke
authors.forename: Jenny C A
authors.initials: JC
authors.lastname: Read
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003867:Depth Perception / Q000502:physiology; D004172:Diplopia / Q000517:prevention & control; D005099:Exotropia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult