Disorders of vertical optokinetic nystagmus in patients with ocular misalignment.
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.
Garbutt
Siobhan
S
Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Trust, and Institute of Child Health, WC1N 1EH, London, UK.
Han
Yanning
Y
Kumar
Arun N
AN
Harwood
Mark
M
Rahman
Rahim
R
Leigh
R John
RJ
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