title: Refractive anomalies and visual activation in functional magnetic resonance imaging (fMRI): a versatile and low-cost MR-compatible device to correct a potential confound.
abstract: OBJECTIVE
  To develop a magnetic resonance (MR)-compatible, versatile, easy-to-use, and low-cost device for refractive correction.
  
  
  METHODS
  We retrospectively evaluated the application and practicability of the refractive correction in 110 subjects who had participated in various functional MR imaging (fMRI) studies with complex visual stimulation paradigms since the introduction of the MR-compatible lens frame at our site. The subjects consisted of 31 patients with Parkinson's disease (age range, 40-85; mean age, 63.2 years) and 79 healthy volunteers (age range, 18-79; mean age, 46.7 years).
  
  
  RESULTS
  In volunteers, experimentally induced myopia caused a substantial (>20%) reduction of the blood oxygenation level dependent (BOLD) response to a flickering dartboard.
  
  
  CONCLUSIONS
  Refractive errors (and the resulting optical blur) may play a nonnegligible role as a possible interfering factor in fMRI experiments with visual stimuli. The MR-compatible frame (fitted with appropriate lenses) used in this study affords full refractive correction at reasonable cost and preparation time.
authors.affiliation: Max Planck Institute of Psychiatry, Magnetic Resonance Study Group, Munich, Germany.
authors.forename: Gregor-K
authors.initials: GK
authors.lastname: Elbel
authors.forename: Christian
authors.initials: C
authors.lastname: Kaufmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Schaefers
authors.forename: Anne
authors.initials: A
authors.lastname: Buser
authors.forename: Dorothee P
authors.initials: DP
authors.lastname: Auer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001931:Brain Mapping; D016022:Case-Control Studies; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology; D010300:Parkinson Disease / Q000503:physiopathology*; D019047:Phantoms, Imaging; D010775:Photic Stimulation; D011305:Presbyopia / Q000503:physiopathology; D012029:Refraction, Ocular; D012189:Retrospective Studies; D014792:Visual Acuity