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
My Aim
- To get some idea how to communicate during the test situation
- To get some idea about the child's visual capacity
- To get some idea about the dhilc's capacity to compensate for visual loss
- To get some idea if and how the child's vision can attribute to alternative communication as pictures of sign language later on
Optimal conditions for visual assessment
- Time of the day
- Home-like environment
- Establishment of interraction with respect to finding ways for non-verbal communication; such as pointing with best functioning part of the body, different sounds, sorting, fetching things
- Prepare the child with information
- Keep promises
Optimal time
- Meet the child at the time when it is most receptive
- Make sure you have enough time
- Without siblings
- No clashes with fixed times for other clinics on the same day
Secure convenient surroundings
- Waiting room
- Assessment room with sofa
- Physical contact with well-known people
Observations during the meeting
- Child feels safe and confident?
- Spontaneous activity started by child?
- Facial expression - happy, seldom?
- Typical features?
First meeting
Try to get introduced by somebody the child relies upon.
Talk with a varying voice; present yourself, at near distance, address him with his name, eg; "hello Peter"
- Avoid wearing a white coat
- Introduce yourself as a person, not a profession, since a profession, eg; eye doctor, relates to problems with eye drops
- Ask to say hello by tirght hand touch, left hand, right foot, left foot and observe what's going on.
Reflections
- Does the child hear and understand?
- How does the child answer?
- Best motor capacity?
- Does s/he see and hear and the same time?
- Does s/he see and move at the same time?
- Is there hand-eye coordination?
Information about the assessment room
- The child enters together with a well-known person
- Give the child plenty of time for accommodation and exploration of the unknown room
- Share attention with the child to objects by making remarks
- Report which people are in the same room as the child.
Information about what we expect him to do and why
Observations
- Spectacles in use?
- Eye contact established?
- Close-looking behaviour?
- Nystagmus?
- Head positioning?
- Tonic neck reflex?
- Paresis?
- Which side of the body is the best?
- Athetosis?
- Can the child grasp and catch?
- Maintain holding?
- Move around without assistance?
Problems caused by:
- motor reflexes as opistotonus, TNR (tonic neck reflex)
- difficulties with head positioning and trunk instability
- short mind absences - petit mal epilepsy
- insufficient screening of noises and movements in the peripheral visual field
What is the strongest most motiviating ability?
- Vision?
- Hearing?
- Touch?
- Smell?
- Mobility?
- Vibration?
Observe:
- The way the child reacts to new situations
- The child's interactions with its parents, assistant teacher
- The parents', assistant's means to tempt the child to participate
- The parents', assistant's means to maintain the child's concentration
- What are the disturbing factors; unexpected sounds, people in motion, epilepsy
- Is there close looking behaviour?
- Hand-eye coordination?
- Suspicion of visual field defect?
- Light adaptation problems?
- Motor possibilities
- CVI problems for instance when the child is asking for the assistant who is already sitting beside him.
What to bear in mind
- the tests are interesting and at an appropriate level
- Enough time
- Tempo
- Breaks
Some questions to bear in mind when doing visual assessment
Which sense is the dominant one for the person?
Which sense would stimulate their interest to look?
Dominant sense - supporting sense - for far distance and near distance
Which sense informs about where an object is?
Which sense does the child use primarily to recognise people, surroundings or objects?
Expected visual problems
- Eye movement disturbances
- Accommodation problems
- Spectacles related problems
- Low vision
- Problems with recognition due to brain abnormality
1 Eye movements
- Varying degree of strabismus (squint) - may be with diplopia (double vision)
- Nystagmus - Blocking; Compensative head positioning
- Follow movements (sacchades) - with eyes or head?
- Ptosis?
- Fixation - type - foveal; stable, excentric; delay, duration
2 Lens accommodation
- Corresponding to age = normal
- Spastic
- Tonic
- Lack of accommodation ability cause by; drugs to treat epilepsy, travel sickness, salivation; cataract operation
Spectacles
Used to correct myopia, hyperopia, astigmatism4 Low vision problems with recognition abnormality
Subfunctions of vision
- Sphere of interest for vision
- Eye movements
- Visual acuity
- Visual field
- Contrast sensitivity
- Colour vision
- Light and dark adaptation
- Stereopsis
- Perceptions
Visual sphere of interest
How to get a child to use vision: toy preference - hard or soft; balls, cars, dolls, animals; sound feedback - what action rewards with sound
Does the child react to lights or shiny things?
At which distance does the child fixate and follow things?
Does the child need sounds to look at toys? Vibration could be a way to start looking; to show hand-eye coordination
When the child fixates does s/he follow with eyes or head? A toy moving slowly can be interested int look at and follow. A rapid movement can be interesting to detect as well.
Visual acuity
Grating tests: You can't compare the value from a grating test with the value from a symbol test because the differences in the areas stimulated.
Test of optotypes: For near vision and far vision; one eye and both eyes; with and without glasses; single symbols or letters symbols or letters in lines.