title: Static ocular counterroll: video-based analysis after minimizing the false-torsion factors.
abstract: OBJECTIVE
  To determine the validity and usefulness of a newly developed measurement method of static ocular counterrolling (s-OCR) that eliminates false-torsion factors and to test the Jampel hypothesis that s-OCR does not exist.
  
  
  METHODS
  A lightweight measurement device, consisting of a video camera, a coaxial light source, and a laser pointer projecting a fixation target on the wall, was fixed to a subject's head by means of a mouthpiece. In 11 healthy adults (mean age: 30 +/- 15 years), digital images of the right eye were captured while the subject kept his head tilted at a randomly selected angle ranging from 0 degrees to 50 degrees . By a frame-by-frame analysis of movements of the corneal light reflex and the iris patterns, OCR was evaluated.
  
  
  RESULTS
  Torsional eye movement in the opposite direction to head tilt was found in all subjects. The amount of torsion continuously increased until the head-tilt angle reached 40 degrees. The average (+/- SD) amplitude of a fitted sine curve was 7.6 +/- 3.2 degrees (range: 4.3 degrees-10.3 degrees), and the individual amplitude was significantly larger than the test-retest repeatability of the measurement (+/-1.7 degrees).
  
  
  CONCLUSIONS
  The measurement method used in this study provided good test-retest repeatability and ease of application. The characteristics of torsional eye movements that we observed after minimizing the false-torsion factors agree with previous reports supporting the existence of s-OCR.
authors.affiliation: Department of Ophthalmology, Okayama University, Graduate School of Medicine and Dentistry, Okayama, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hamasaki
authors.affiliation: Department of Ophthalmology, Okayama University, Graduate School of Medicine and Dentistry, Okayama, Japan. shasebe@md.okayama-u.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hasebe
authors.affiliation: Department of Ophthalmology, Okayama University, Graduate School of Medicine and Dentistry, Okayama, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohtsuki
mesh_terms: D000328:Adult; D003290:Convergence, Ocular / Q000502:physiology*; D003867:Depth Perception / Q000502:physiology*; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D011187:Posture / Q000502:physiology*; D012016:Reference Values; D014102:Torsion Abnormality; D014743:Videotape Recording; D015348:Vision, Binocular / Q000502:physiology