University of Edinburgh

Assessing Vision in Children with Additional Support Needs: Why and How?

Presented on Wednesday 31 October, 2012
J Margaret Woodhouse School of Optometry & Vision Sciences

Refractive errors


Accommodation - focusing for near


Accommodation reduces with age

accommodation with age

Short-sight (myopia)


A short-sighted child:

  • Lenses to correct myopia (short-sight) are negative, eg; -5.00D, -7.50D.
  • Will have clear vision at near and blurred vision at distance.
  • Will need to wear glasses for distance, eg; watching television and looking at the board.
  • May choose to wear glasses all the time.
  • May use eyes 'natural magnification' by removing specs for near.

Long-sight (hypermetropia)


A long-sighted child:

  • Lenses to correct hypermetropia (long-sight) are positive; eg; + 2.25D, +6.75D.
  • Vision will be clearer at distance and more blurred or uncomfortable vision at near.
  • Long-sighted children can often accommodate or focus to see clearly without their glasses but will probably not be able to sustain this for long.
  • Extent of blur or discomfort will depend on age as well as amount of long-sight.
  • May need to wear glasses for near.
  • May need to wear glasses all the time


chart for astigmatism


A child with astigmatism

  • The astigmatic (cylindrical) component of the lens is the second figure of the prescription, and the direction of the astigmatism the third part; eg -1.00/+0.50 x 90 +3.50/-1.25 x 45.
  • Will have blurred vision at all distances.
  • May need to wear glasses for both distance and near.
  • May find adjusting to the glasses very difficult.

In general, if the second figure is small compared to the first, the important aspect is myopia or hypermetropia
-6.50/+1.75 x 30 means myopia
+4.50/+0.75 x 10 means hypermetropia

If the second figure is large compared to the first, astigmatism is the most important aspect +1.50/-4.25 x 175 means astigmatism.

Lenses to correct myopia minify the eyes, while lenses to correct hypermetropia magnify.

Children with visual impairment

children with VI

children with VI

children with VI

children with VI

Du et al (2005) Retrospective Analysis of Refractive Errors in Children with Visual Impairment. Optometry & Vision Science, 82, 807-816

Children with additional needs re much more likely to have either long sight or short sight (and/or astigmatism) and need to wear glasses

HOW do professionals assess vision?

Measuring long and short-sight - Refraction



long sight


short sight

HOW can school staff assess vision?

What would make us suspect refractive error?

  • Short-sight
    Getting very close to things
    Screwing eyes up to see at distance
    Lack of interest at distance
  • Long-sight
    Getting very close to things
    Lack of interest in near tasks
  • Astigmatism
    Getting very close to things

Usually, it is NOT possible to spot a refractive error in a child - all children should have an examination

HOW can school staff help?

  • By encouraging children to wear their glasses.
  • Children with additional needs may have differently shaped faces to 'ordinary' children.
  • Children with cerebral palsy may have poor head control that means glasses slip or are knocked around by the head support
  • Because of limited mobility and hand-eye coordination, children may find adapting to lenses difficult.

Wearing glasses

There are two reasons to wear glasses and LOTS of reasons to reject glasses

  1. Glasses make the world appear clearer
    To the child, this means that things look 'different'
    The lenses magnify or minify and distances are difficult to judge
    All lenses have distortions - the stronger the prescription, the greater the distortions.
  2. Glasses reduce the effort to see clearly and may reduce a squint
    To the child the glasses may make no visible difference.

Encouraging a reluctant child

  • Avoid curl sides and sports bands.
  • Know what the glasses are for and when the child will get benefit.
  • Pick a favourite activity with undivided attention - this is going to be 'spec wearing time'.
  • Put glasses on and start the activity.
  • If your child takes the glasses off, end the activity without comment.
  • Gradually build up wearing time - don't worry if it takes weeks or even months.