title: Global motion perception in 2-year-old children: a method for psychophysical assessment and relationships with clinical measures of visual function.
abstract: OBJECTIVE
  We developed and validated a technique for measuring global motion perception in 2-year-old children, and assessed the relationship between global motion perception and other measures of visual function.
  
  
  METHODS
  Random dot kinematogram (RDK) stimuli were used to measure motion coherence thresholds in 366 children at risk of neurodevelopmental problems at 24 ± 1 months of age. RDKs of variable coherence were presented and eye movements were analyzed offline to grade the direction of the optokinetic reflex (OKR) for each trial. Motion coherence thresholds were calculated by fitting psychometric functions to the resulting datasets. Test-retest reliability was assessed in 15 children, and motion coherence thresholds were measured in a group of 10 adults using OKR and behavioral responses. Standard age-appropriate optometric tests also were performed.
  
  
  RESULTS
  Motion coherence thresholds were measured successfully in 336 (91.8%) children using the OKR technique, but only 31 (8.5%) using behavioral responses. The mean threshold was 41.7 ± 13.5% for 2-year-old children and 3.3 ± 1.2% for adults. Within-assessor reliability and test-retest reliability were high in children. Children's motion coherence thresholds were significantly correlated with stereoacuity (LANG I & II test, ρ = 0.29, P < 0.001; Frisby, ρ = 0.17, P = 0.022), but not with binocular visual acuity (ρ = 0.11, P = 0.07). In adults OKR and behavioral motion coherence thresholds were highly correlated (intraclass correlation = 0.81, P = 0.001).
  
  
  CONCLUSIONS
  Global motion perception can be measured in 2-year-old children using the OKR. This technique is reliable and data from adults suggest that motion coherence thresholds based on the OKR are related to motion perception. Global motion perception was related to stereoacuity in children.
authors.affiliation: Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand.
authors.forename: Tzu-Ying
authors.initials: TY
authors.lastname: Yu
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Jacobs
authors.forename: Nicola S
authors.initials: NS
authors.lastname: Anstice
authors.forename: Nabin
authors.initials: N
authors.lastname: Paudel
authors.forename: Jane E
authors.initials: JE
authors.lastname: Harding
authors.forename: Benjamin
authors.initials: B
authors.lastname: Thompson
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002675:Child, Preschool; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D017120:Nystagmus, Optokinetic; D011601:Psychophysics; D015203:Reproducibility of Results; D012684:Sensory Thresholds; D014787:Vision Tests / Q000379:methods*; D014792:Visual Acuity / Q000502:physiology*
keywords: dorsal stream; motion coherence threshold; optokinetic nystagmus; random-dot-kinematogram; vision