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
- Infections during foetal stage or later on
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?
Impaired visual acuity can depend on
Disturbances in light
Damage to the retina
Damage to the visual pathway
Damage to the brain
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 pathwayAbnormalities 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