title: Relative roles of luminance and fixation in inducing dissociated vertical divergence.
abstract: OBJECTIVE
  We evaluated the roles of luminance and fixation in the pathophysiology of dissociated vertical divergence (DVD).
  
  
  METHODS
  Vertical eye position was measured in 6 subjects with DVD (ages 11-47 years, 5 females) and 6 controls (ages 16-40 years, 5 females) using video-oculography (VOG) under conditions of change in fixation and luminance.
  
  
  RESULTS
  Subjects with DVD showed the following VOG responses. When fixation was precluded with a translucent filter and bright light was shone into one eye to produce a marked binocular luminance disparity, we found some subjects had a small induced vertical divergence causing the illuminated eye to be lower than the nonilluminated eye (mean -1.6° ± 1.5°, P = 0.06 compared to no vertical divergence using the signed rank test). When fixation was precluded with a translucent filter, while alternate occlusion produced a mild binocular luminance disparity, we found a smaller vertical divergence of the eyes that was not statistically significant (1.2° ± 2.1°, P = 0.3). When alternate occlusion produced reversal of monocular fixation in the dark (with essentially no change in peripheral luminance disparity), there was a significant vertical divergence movement causing the covered eye to be relatively higher than the uncovered eye (7.2° ± 3.1°, P = 0.03). The amplitude of this vertical divergence was similar to that measured under conditions of alternate occlusion in a lighted room (where there also was a significant average relative upward movement of the covered eye of 8.1° ± 2.9°, P = 0.03). Control subjects showed no vertical divergence under any testing conditions.
  
  
  CONCLUSIONS
  Dissociated vertical divergence is mediated primarily by changes in fixation and only to a minor degree by binocular luminance disparity.
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States Department of Ophthalmology, St. Louis University Eye Institute, St. Louis, Missouri, United States.
authors.forename: Rafif
authors.initials: R
authors.lastname: Ghadban
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States.
authors.forename: Laura
authors.initials: L
authors.lastname: Liebermann
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States.
authors.forename: Lindsay D
authors.initials: LD
authors.lastname: Klaehn
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Holmes
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Brodsky
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008029:Lighting / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D013285:Strabismus / Q000503:physiopathology*; D015348:Vision, Binocular / Q000502:physiology*; D055815:Young Adult
keywords: DVD; dissociated vertical divergence; strabismus; videooculography