University of Edinburgh
 

Course: Visual Assessment of Children: The Orthoptist Role

Presented on Wednesday 9 February 2005

Case study 2

Gillian Coyle, Senior Orthoptist

Functional Vision Assessment Report

Name: Loki
Date of Birth: [age 11]
Address:
Date of Assessment: dd/mm/yy

Assessors:

Dr Margot Campbell, Staff Grade Paediatrician
Mrs Gillian Coyle, Orthoptist
Mrs Eunice Ridley, Specialist Teacher, Visual Impairment Service

Loki attended the functional vision assessment clinic at Metatron School with his mother. Loki is known to have a degree of visual impairment and is registered partially sighted. The purpose of this assessment is to update on his present visual abilities as he moves to secondary school later this year. He was referred by Dr Almaghrabi, his community paed1atrician. The information is for his teachers to ensure appropriate educational strategies are in place for him.

Past Medical History
Loki is a twin who was born prematurely at thirty-two weeks. He had a stormy neonatal period. He sustained an intraventricular haemorrhage which led to hydrocephalus. A shunt was inserted to relieve this. Associated with these early problems, scans have shown Loki to have a condition known as periventricular leucoma1acia. People with this condition are at increased risk of cerebral visual impairment.

Loki also has cerebral palsy in the form of ataxic diplegia, he bas epilepsy and learning difficulties.

Ophthalmic History
Loki attends the eye clinic at PRI. He bas glasses for constant use. He has also in the past had a functional vision assessment at Professor Dutton's clinic at Yorkhill in Glasgow.

There are two causes of Loki's visual difficulties. Firstly he has bilateral optic nerve atrophy, which affects the visual information passing from the eye to the brain. He also has cerebral visual impairment caused by damage to some of the visual pathways within the brain.

Loki and his Mother's Impression of Vision
On the whole Loki copes extremely well despite his difficulties. He does have a tendency to trip over objects in front of him. He also has a tendency to bump into doorways and can do so on either side. He has no problem on familiar steps but does have difficulty judging unfamiliar steps. He has difficulty distinguishing a line from a step and is wary changing surfaces and crossing cracks on the pavement.

Loki has no difficulty recognising people and can do so from across the room. He can identify people in photographs, tending to peer at them, and can recognise himself. Loki bends over his work to look at it close up. He sits close to the television (within a metre). He prefers simple animation such as Noddy and is not keen on fast moving cartoons. Loki has difficulty seeing things out of the car window. He prefers looking down at his knees inside the car as he finds the fast moving outside scene to much to cope with.

Loki finds his way in familiar places such as his own home. He has a poor sense of direction however when out and about. He often forgets where he has put things.

Loki has no difficulty recognising familiar objects and he knows the basic shapes. He has no difficulty with colours. Loki does however have difficulty identifying objects against a patterned background or in a busy visual scene.

The Assessment

Visual Acuity
This is a measure of the ability to see details at maximum contrast in optimum conditions. The tests used were the Lea Symbols for distance and near. Loki was tested wearing his glasses.

Distance vision
- 6/19, this means in practical terms that Loki needs to be about a meter away, to see details a person with normal vision would see at about three meters. Near - symbol size 6/19 at 12 cms, eg; 0. However, Loki was peering closely at this and much larger material should be used in practical situations.

Contrast Sensitivity
This is a measure of the ability to see shades of grey against a white background The tests used were

Hiding Heidi - at 6 meters contrast sensitivity measured 10% which is significantly reduced.
Lea low contrast symbols - at 20 cms contrast sensitivity measured 2.5% which is slightly reduced.

Visual Field
This is the area over which one can see without moving the head or eyes. Our impression was that Loki has a general constriction of his visual field, particularly the lower field.

Cover Test and Binocularity
This is the test for squint. A right convergent squint was noted. There is absence of binocular vision associated with this.

Eye Movements
Loki has a full range of smooth pursuit (or following) eye movements. He moves his eyes more slowly than normal and needs time to do this. Saccades are rapid eye movements to look between objects. These movements are initiated well b~ tend to undershoot the target, requiring other adjusting eye movements to gain sight of the object.

Cerebral Vision
This is the way the brain processes and makes sense of visual information. Loki has several problems in this area.

  • Difficulty in seeing parts of an image against a complex background. Loki has much greater difficulty in seeing objects in a busy visual scene than his visual acuity alone would suggest, eg; he can find a toy car against a plain background, but placed on the busy town mat" he was unable to find the car even close up.
  • Impaired depth perception. This leads to difficulty on pnfclmi1iar stairs and in knowing whether the crack 00 the pavement is a step or not. Loki's other difficulties of reduced visual acuity, reduced contrast sensitivity, lack of binocular vision and visual field constriction also contribute to mobility problems and explain why Loki has a tendency to trip over objects and bump into things.
  • Impaired perception of movement. This is difficulty in seeing and interpreting fast movement, such as fast moving cartoons or the scene out of the moving car window. Loki also needs time to move. his eye$ to accurately locate objects which contributes to this difficulty.
  • Problems with orientation. Loki has mild difficulties in this area manifesting as poor sense of direction and difficulty remembering where he has put things.

In Summary

Loki has reduced visual acuity and reduced contrast sensitivity. His visual field is generally constricted particularly inferiorly.

Loki has minor difficulties with eye movements and in general needs more time to take in a visual scene and to process visual information.

Loki has difficulties with seeing objects against a complex background (figure/ground difficulties). He has impaired depth perception and difficulties with perception of movement. He has mild orientation difficulties.

Recommendations

Classroom

  • Provide small amounts of information sequentially against a plain static background.
  • Items and ideas should be presented singly.
  • Use large scale material with bold colour and contrast.
  • Extra time needs to be given to process visual information and to react to it.
  • Moving visual stimuli should be slow and across a static background.
  • Pictures should be simple and uncluttered.
  • Using touch to locate objects and to "keep the place" can be helpful.
  • Keeping "everything in its place" can aid visual memory to remember where objects have been put.

Mobility

  • Mobility training should be ongoing to improve confidence and promote Independence.
  • A coloured strip on the edge of steps in school may help identify them as steps.
  • Describing the route verbally as he goes along can help by using auditory memory as well as visual memory in learning new routes.

We would be very happy to discuss any aspects of this report with Loki's parents or with any of the professionals involved with him.

Dr Margot Campbell Staff Grade Paediatrician