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Vision and Mobility

Locomotor strategies are planned using information acquired by intermittent visual sampling of the environment, which means the visual system is free to attend to other things. This highlights that where and when we look are key factors in our ability to safely negotiate changing terrains. It also highlights that visual impairment that results in impoverished information about the environment may lead to the adoption of unsafe locomotion strategies

null The right-hand image shows what stairs look like to someone with hemianopia.

Objectives

How is landing behaviour affected by visual impairment when stepping down?

To understand what, where and how different aspects of visual (and other sensory) information is used to regulate locomotion and posture in various environments and ambient conditions.

For example:

  • How correctable visual impairment such as refractive blur and cataract effects balance control and movement strategy during stair negotiation
  • How multifocal spectacle use effects gait over obstacles and/or during transition to a new level
  • How the removal of binocular vision effects movement planning and control
  • What peripheral versus central cues are used to plan and control movement

The Lab in Action

motion lab The motion-tracking lab in action. On the left, a subject is fitted with reflective motion tracking tags. In the middle, he steps onto a small platform. On the right, the motion-tracker uses the information to reconstruct the subjects position and stance.

The lab quantifies human movement using a 6 camera Vicon MX3 motion analysis system, and 2 AMTI forceplatforms. Adaptations in movement pattern are quantified using various biomechanical models

Visual Impairment and Falls

Multifocal lens wearers are twice as likely to fall as single vision lens wearers. This is likely to be because low level objects are out of focus when viewed though the intermediate or near addition part of lens.

In the UK over 2m falls each year result in hospital treatment. Of these, almost 10% of cases are linked to visual impairment, with the majority being elderly individuals 65 yrs and above. It is estimated that up to 80% of this visual impairment is correctable via refractive correction (40%) or cataract removal (37%). Although it is known that visual impairment is a risk factor for falls, little is known about how visual impairment affects postural stability and obstacle & step/stair negotiation. Even when vision is optimally corrected, the use of multifocal spectacles has been linked to increased risk of falls.

Funding

Our research is funded by the EPSRC, Department of Health, The Health Foundation, College of Optometrists and Vicon Motion Systems Ltd. We also undertake contract research and consultancy.

  • (£125k) Project Grant, EPSRC (2009-11) Sensorimotor mechanism used by lower limb amputees to control their prosthesis.
  • Doctoral Training Award, EPSRC (2010). Sensorimotor control mechanisms used by lower-limb amputees during adaptive locomotion.
  • (£59k) Research collaboration grant - matching funding from Vicon Motion Systems Ltd and the Federation of Ophthalmic and Dispensing Opticians (2006) The Effects of Ophthalmic Interventions on Balance and Mobility.
  • (£54k) Doctoral Training Grant, College of Optometrists (2006 - 09) Monocular versus binocular vision on dynamics of stepping.
  • (£157k) Training Fellowship Grant, The Health Foundation (2005) Impact of correctable visual impairment upon balance and mobility in elderly and young subjects.
  • (£211k) Researcher Development Award (Doctoral Training), Department of Health (2005) Effects of common forms of visual impairment upon postural stability and gait biomechanics during stair/step negotiation in the elderly.
  • Doctoral Training Award, EPSRC (2004). The effects of monocular versus binocular visual blur on lower-limb biomechanics during gait and stair negotiation.
  • Doctoral Training Award, EPSRC (2002). The biomechanics of gait initiation in individuals with lower limb amputation.
  • Summer Research Scholarship, College of Optometrists (2003, 2004 and 2005).
  • (£143k) Project Grant, PPP Healthcare (2002) Falls in the elderly: the link with visual impairment and ophthalmic intervention.
  • Small Equipment Grant, The Visual Research Trust (2002).
  • (£100k) HEFCE Capital Bids Grant (2001) Initial build/establishment of lab; included the purchase of a 5-camera 3D Vicon Motion Analysis System, 2 forceplatforms, and laboratory modification to allow wheelchair access.

Investigators

  • Professor David Elliott
  • Dr. John Buckley
  • Mr. Andy Scally (Medical Statistics)
  • Louise Johnson (Rehabilitation Studies, SoH)
  • Valentina Graci (Ph.D student)
  • Eve Panesar (PhD student)
  • Mat Timmis (Ph.D student - Medical Engineering)