title: Effect of bilateral macular scotomas from age-related macular degeneration on reach-to-grasp hand movement.
abstract: OBJECTIVE
  Vision plays a critical role in reaching and grasping objects. Consequently, bilateral macular scotomas from age-related macular degeneration (AMD) may affect reach-to-grasp movements. The purpose of this work was to investigate changes in reach-to-grasp movement dynamics and to relate those changes to the characteristics of subjects' preferred retinal loci (PRL), scotomas, and visual acuities.
  
  
  METHODS
  Three-dimensional positions of the index finger and thumb were recorded while subjects with bilateral scotomas and subjects with normal vision reached for and grasped blocks of three widths at two distances under binocular and monocular viewing conditions. Reach-dynamic parameters and the grip aperture (thumb-index finger distance) were calculated. Retinal locations and sizes of subjects' scotomas and PRLs were mapped with a scanning laser ophthalmoscope.
  
  
  RESULTS
  Scotoma subjects' hand trajectories had longer movement durations, lower maximum velocities, and longer visual reaction times than those of control subjects. With monocular viewing, maximum grip aperture (MGA) increased as a function of block width at a significantly higher rate for scotoma subjects than for control subjects. MGA decreased with increasing PRL bivariate normal ellipse area, and visual reaction time increased with decreasing acuity of the eye tested.
  
  
  CONCLUSIONS
  Compared with normally sighted subjects, subjects with bilateral macular scotomas from AMD have reach-to-grasp movements with longer trajectories, longer visual reaction times, lower velocities, and altered MGA-block width scaling. Visual reaction time and MGA are directly related to PRL characteristics. Deficits in reach-to-grasp movement caused by macular scotomas are greater in degree than those reported by others for real or artificial peripheral scotomas.
authors.affiliation: Kansas City Veterans Affairs Medical Center, Kansas City, Missouri, 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: Barbara M
authors.initials: BM
authors.lastname: Quaney
authors.forename: Susan A
authors.initials: SA
authors.lastname: Grose
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Maino
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D007839:Functional Laterality; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008266:Macula Lutea / Q000503:physiopathology*; D008268:Macular Degeneration / Q000503:physiopathology*; D009068:Movement / Q000502:physiology*; D009069:Movement Disorders / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time; D012607:Scotoma / Q000503:physiopathology*; D013647:Task Performance and Analysis; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology