title: Disorders of vertical optokinetic nystagmus in patients with ocular misalignment.
abstract: OBJECTIVE
  To compare responses to vertical and horizontal optokinetic (OK) stimulation in patients with disorders of ocular alignment.
  
  
  METHODS
  Using the magnetic search coil technique, we measured horizontal and vertical rotations of both eyes in six patients with strabismus since childhood and eight normal subjects. The OK stimulus subtended 72 degrees horizontally and 60 degrees vertically, consisted of black-and-white stripes with a spatial frequency of 0.04 cycles/degree, and moved either vertically or horizontally at 22.5 or 12 degrees/s. All patients and controls were tested with both eyes viewing and monocularly.
  
  
  RESULTS
  Vertical OK responses were asymmetric in most normals and patients. The direction of this asymmetry varied between individuals, but upward stimuli more commonly elicited a greater response than downward stimuli. Monocular horizontal OK responses were symmetric in normals; patients showed either an asymmetry with greater responses for nasal motion, or a directional bias. During monocular and binocular viewing, vertical OK stimulation induced vertical nystagmus in normal subjects, but all patients showed diagonal responses, with horizontal components that were significantly greater than controls. The inappropriate horizontal component of the response increased at the higher stimulus speed, and was not simply due to latent nystagmus.
  
  
  CONCLUSIONS
  Patients with disorders of ocular alignment since childhood show an inappropriate horizontal response to vertical OK stimuli, indicating directional abnormality of either motion vision pathways or the ocular motor response.
authors.affiliation: Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Trust, and Institute of Child Health, WC1N 1EH, London, UK.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Garbutt
authors.forename: Yanning
authors.initials: Y
authors.lastname: Han
authors.forename: Arun N
authors.initials: AN
authors.lastname: Kumar
authors.forename: Mark
authors.initials: M
authors.lastname: Harwood
authors.forename: Rahim
authors.initials: R
authors.lastname: Rahman
authors.forename: R John
authors.initials: RJ
authors.lastname: Leigh
mesh_terms: D000293:Adolescent; D000328:Adult; D000550:Amblyopia / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017120:Nystagmus, Optokinetic; D010775:Photic Stimulation / Q000379:methods; D012399:Rotation; D013285:Strabismus / Q000503:physiopathology*; D015348:Vision, Binocular; D015349:Vision, Monocular; D014792:Visual Acuity; D014795:Visual Pathways / Q000503:physiopathology