title: Visual contrast response functions in Parkinson's disease: evidence from electroretinograms, visually evoked potentials and psychophysics.
abstract: OBJECTIVE
  Visual contrast detection thresholds and suprathreshold contrast discrimination thresholds were compared to luminance and flash/pattern electroretinograms (ERG) and visually evoked potentials (VEP) in patients with Parkinson's disease (n = 31), patients with multiple system atrophy (n = 6), patients with progressive supranuclear palsy (n = 6) and control patients without central nervous disease (n = 33).
  
  
  METHODS
  The stimuli were luminance modulated full-field (flash) or horizontally oriented sinewave gratings (pattern), the latter having either a low (0.5 cycles/deg) or medium (4.0 cycles/deg) spatial frequency. Stimulus contrast ranged from 10 to 80% so that contrast response functions could be derived.
  
  
  RESULTS
  Contrast thresholds were higher in the patients with Parkinson's disease than in the control patients. Contrast discrimination thresholds were also somewhat elevated in patients with Parkinson's disease. Pattern ERG amplitudes were significantly reduced in patients with Parkinson's disease for the medium spatial frequency stimulus, but less for the low spatial frequency and flash stimuli.
  
  
  CONCLUSIONS
  Our results suggest that Parkinson's disease impairs contrast processing in the retina. VEP amplitudes did not significantly differ between the groups for the conditions tested. Patients with progressive supranuclear palsy also showed impaired contrast perception and reduced ERG amplitudes, whereas patients with multiple system atrophy were less impaired.
authors.affiliation: Neurologische Universitätsklinik, Universität Freiburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Langheinrich
authors.forename: L
authors.initials: L
authors.lastname: Tebartz van Elst
authors.forename: W A
authors.initials: WA
authors.lastname: Lagrèze
authors.forename: M
authors.initials: M
authors.lastname: Bach
authors.forename: C H
authors.initials: CH
authors.lastname: Lücking
authors.forename: M W
authors.initials: MW
authors.lastname: Greenlee
mesh_terms: D000368:Aged; D015350:Contrast Sensitivity; D004596:Electroretinography; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000503:physiopathology; D010300:Parkinson Disease / Q000503:physiopathology*; D010775:Photic Stimulation; D011601:Psychophysics; D012016:Reference Values; D012684:Sensory Thresholds; D013494:Supranuclear Palsy, Progressive / Q000503:physiopathology; D014796:Visual Perception / Q000502:physiology*