title: Visual Contrast Sensitivity in Early-Stage Parkinson's Disease.
abstract: OBJECTIVE
  Visual impairments are frequent in Parkinson's disease (PD) and impact normal functioning in daily activities. Visual contrast sensitivity is a powerful nonmotor sign for discriminating PD patients from controls. However, it is usually assessed with static visual stimuli. Here we examined the interaction between perception and eye movements in static and dynamic contrast sensitivity tasks in a cohort of mildly impaired, early-stage PD patients.
  
  
  METHODS
  Patients (n = 13) and healthy age-matched controls (n = 12) viewed stimuli of various spatial frequencies (0-8 cyc/deg) and speeds (0°/s, 10°/s, 30°/s) on a computer monitor. Detection thresholds were determined by asking participants to adjust luminance contrast until they could just barely see the stimulus. Eye position was recorded with a video-based eye tracker.
  
  
  RESULTS
  Patients' static contrast sensitivity was impaired in the intermediate spatial-frequency range and this impairment correlated with fixational instability. However, dynamic contrast sensitivity and patients' smooth pursuit were relatively normal. An independent component analysis revealed contrast sensitivity profiles differentiating patients and controls.
  
  
  CONCLUSIONS
  Our study simultaneously assesses perceptual contrast sensitivity and eye movements in PD, revealing a possible link between fixational instability and perceptual deficits. Spatiotemporal contrast sensitivity profiles may represent an easily measurable metric as a component of a broader combined biometric for nonmotor features observed in PD.
authors: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Wendy
authors: W
authors: Ming
authors: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Dimitrios J
authors: DJ
authors: Palidis
authors: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada 2International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada 3Djavad Movafaghian Center for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada 4Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Miriam
authors: M
authors: Spering
authors: Djavad Movafaghian Center for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada 4Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, British Columbia, Canada 5Division of Neurology and Pacific Parkinson's Research Centre, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Martin J
authors: MJ
authors: McKeown
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D010300:Parkinson Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D010775:Photic Stimulation; D012720:Severity of Illness Index; D014741:Video Recording; D014786:Vision Disorders / Q000209:etiology / Q000503:physiopathology*