University of Edinburgh
 

Vision Assessment of Children and Young People at a Developmentally Early Stage

Thursday, 6th June, 2002

Jan Björkman, Ingeborg Stenström, Göran Cedermark

Swedish Institute for Special Needs Education

What should we think about?

Vision is an important factor for development

Therefore we have to check

  • if vision is normal and could be used for alternative communication
  • or not normal or absent, so that we have to find out the best way to optimal development based on the child's capacity.
  • That needs teamwork.

Some causes of visual impairment in non-verbal people

  • Prematurity with CP (cerebral palsy), PBL (periventricular leucomalacia) and optic nerve atrophy
  • Hereditary diseases
  • Marlformations
  • Infections during foetal stage or later on
  • Tumours
  • Accidents

Some important facts to try to get information about

  • At which age did the damage occur?
    - Which developmental capacity and interests did the person have before the illness?
  • Is it getting worse or better?
    - If it's getting worse because of progressive illness will it affect other senses too, for instance hearing?

Questions to be answered during visual assessment

How much visual capacity:

- could one expect based on objective examinations, for instance eye examination, MRI, VEP, ERG;

- does the child show in its behaviour

- does the child show during test situations?

Are there any possibilities to improve visual performance, for instance eye operation, glasses?

We see

  • Form
  • Colour
  • Movement

Impaired visual acuity can depend on

Refractive errors

Disturbances in light

Transmission

Damage to the retina

Damage to the visual pathway

Damage to the brain

Visual Impairment

VI can be due to

  • Damage to the anterior part of the visual pathway OVI (ocular visual imppairment)
  • Damage to the posterior part of the visual pathway CVI (cerebral visual impairment
  • A combination of both OVI and CVI

Anterior damage reduces the quality of the picture

Posterior damage causes varying visual function; reduced quality of the picture and problems with recognition

Damage to anterior visual pathway

Abnormalities located in the eye, optic nerve or tractus optici (OVI). Affects the quality of the picture:
  • Decreased visual acuity, details disappear
  • Decreased contrast sensitivity - faint shadows disappear - flat picture
  • Visual field defect - central, peripheral - patchy picture
  • Changes in colour vision
  • Changes in light adaptation

Recognition is maintained and individuals are functioning better as one would expect

Damage to petwerior visual pathways

Occipital lobe - primary visual centre

Temporal lobe - gives information about what we see (form, colour, recognition)

Parietal lobe - gives information about where objects are in relationship to the body (orientation, hand-eye coordination)

In spite of CVI:

  • Good colour vision
  • Good capacity to see movement
  • Good capacity to see single pictures