University of Edinburgh

Course: Visual Assessment of Children: The Orthoptist Role

Presented on Wednesday 9 February 2005

Low Visual Aid Assessment

Morag McGillivray

Presented on Wednesday 9 February 2005

Moray low vision service

  • Who?
  • What?
  • Where?
  • Why?

Moray Low Vision Service

?to provide the people of Moray with an efficient, effective low vision service that enabled
individuals experiencing a visual loss which couldn?t be corrected by conventional means to
make optimum use of their remaining vision...

  • Accept
  • Adapt
  • Achieve

Low Visual Aids

  • Types of tasks at home, work or school. (near, intermediate, distance)
  • Desired outcome
  • Physical limitations
  • Non-optical aids such as lighting etc.


Size matters!

larger field of vision
X3.9 Larger field of vision, longer working distance

smaller field of vision
X5.4 Smaller field of vision, shorter working distance.

The Low Vision Assessment Preliminary tests include?

  • Ophthalmic examination
  • Refraction Functional vision assessment / orthoptic assessment
  • Contrast Sensitivity
    Snellen test

Contrast Sensitivity

?the ability of the visual system to distinguish between an object and its background...

contrast sensitivity


Text contrast levels

  • Newsprint 60-70%
  • Paperback books 75%
  • Laser printers 94%
    text contrast

Testing Contrast Sensitivity

contrast sensitivity tests


Taking a history...

  • Are there specific educational needs?
  • Does the student work with a visual impairment teacher?
  • Do they use large print workbooks?
  • Can they see the blackboard / whiteboard?
  • Are there computer requirements?
  • Is there access for computer technology adapted for visual impairment?
    taking a history

Keeler ?A? Chart
Keeler A chart


Hand - held magnifiers

  • Portable
  • Relatively inexpensive
  • Wide range of powers (x1.7 to x8)
  • Unsuitable when hand tremor present.
  • Most common type of aid used by school children.

    hand held magnifiers

    hand held magnifiers

  • LED light source provides brighter illumination and clearer, whiter light.
  • Unobtrusive
  • Wide range of powers (x3 to x11)
    hand held magnifiers


Stand Magnifiers

  • Hands free use.
  • Wide range of powers (x3 to x20)
  • Can be used in conjunction with a pencil / pen
  • Bulky
  • Can be difficult to get sufficient lighting.
    stand magnifiers
  • Shadowless light close to the page
  • LED light source
  • Lacks street cred!
    stand magnifiers


Dome magnifiers

  • Sit directly on reading surface
  • Always in focus
  • Available in wide range of shapes and sizes
  • Limited range of power, typically x1.7
    dome magnifiers


Bar magnifiers

  • Semi-cylindrical lenses
  • Magnify one line of print at a time
  • Reduces tracking across page.
  • Limited power
  • Distorted, stretched image.
    bar magnifier


Hands free magnification

  • Ideal for arts and craft
  • Large lens
  • Low power (x1.7)
  • Can be bulky
    hands free magnifiers


Spectacle mounted magnifiers

  • Hands free use
  • Wide range of power
  • Improved design
  • Reduced lens thickness
  • Short working distance
    spectacle magnifiers



  • Designed for intermediate and distance magnification.
  • Lightweight
  • Easy to focus
  • Must only be used when stationary.
  • Can take time to master art of focusing.


Electronic video magnifiers

electronic video magnifiers

The 10 Commandments

  • Thou shalt throw away the rule book.
  • Thou shalt see the child as a whole person and not simply a pair of eyes.
  • Thou shalt always remember the 3 A?s?accept, adapt, achieve.
  • Thou shalt seek advice from those who know the child best.
  • Thou shalt involve the child?s parents whenever possible.
  • Thou shalt not be afraid to experiment.
  • Thou shalt keep it simple.
  • If at first you don?t succeed thou shalt try again ? and again ?
  • Thou shalt never underestimate the power of peer pressure.
  • Thou shalt, wherever possible, provide a spare aid as sometimes the dog eats more than
    just their homework.