title: Preferred retinal locus--hand coordination in a maze-tracing task.
abstract: OBJECTIVE
  Fine manual tasks require coordination of vision, eye movements, and motor control. Macular scotomas from age-related macular degeneration (AMD) may adversely affect this coordination. The purpose of this research was to find whether the preferred retina locus for fixation (fPRL) also guided the hand in performing fine manual tasks and how the fingers, fPRL, and scotomas interacted in task performance.
  
  
  METHODS
  Subjects with bilateral macular scotomas from AMD and normally sighted controls traced an irregular "maze" line pattern with the index finger while viewing their hand and the maze in a scanning laser ophthalmoscope (SLO). Video images from the SLO showing the fingers and maze on the retina during the task were analyzed to produce retinal maps showing the scotoma and bivariate ellipses of fPRL and fingertip retinal positions.
  
  
  RESULTS
  Fingertip retinal ellipses surrounded and were approximately centered on the fPRL ellipses. Fingertip retinal bivariate area was positively correlated with fPRL bivariate area and the percent time the fPRL was on the maze was correlated with visual acuity. Maze-tracing accuracy was positively correlated with saccade rate for scotoma subjects.
  
  
  CONCLUSIONS
  Concentric overlap of fPRL and fingertip retinal ellipses indicates that it is the fPRL that guides the hand in the maze-tracing visuomotor task, just as the fovea guides the fingertip for visually normal subjects. It is likely that factors other than fPRL and scotoma characteristics contribute to poorer maze-tracing performance by scotoma subjects in comparison with controls.
authors.affiliation: Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128, USA. gtimberl@kumc.edu
authors.forename: George T
authors.initials: GT
authors.lastname: Timberlake
authors.forename: Evanthia
authors.initials: E
authors.lastname: Omoscharka
authors.forename: Susan A
authors.initials: SA
authors.lastname: Grose
authors.forename: Rebecca
authors.initials: R
authors.lastname: Bothwell
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D005584:Fovea Centralis / Q000503:physiopathology*; D007839:Functional Laterality; D006225:Hand; D006801:Humans; D008268:Macular Degeneration / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D009887:Ophthalmoscopy / Q000379:methods; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012607:Scotoma / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology