Introduction to Testing Cognitive Vision

Causes of Changes in Processing of Visual Information
Disorders of the Eyes and Anterior Visual Pathways
Lateral Geniculate Nucleus
Processing of Visual Information in the Brain
Early Processing of Visual Information
Processing of Visual Information in Ventral and Dorsal Stream
The Profile of Visual Functioning
Refraction and Spectacles
Factors Affecting the Test Situations
Visual Sphere
Visual Field
Visual Attention
Following Movements and Saccades
Illumination and Position
Video Recordings

Disorders of visual pathways have become the largest group of diseases and traumas that cause visual disability. Children with damage to visual system often also have other more visible problems due to 1) brain damage or 2) diseases and/or traumas in other parts of the body, and 3) changes in the anterior parts of the visual pathways (ROP, optic atrophy). The great variation in the combinations of functional losses leads to highly individual situations in visual and general functioning and thus to great variation in the early intervention and educational needs of children with brain damage related vision loss1. To meet the needs, children’s therapists and teachers should receive more information from the medical services and have further training in the evaluation of visual functioning in preschool and school age because they can add observations that medical services cannot make.

This introduction to visual processing is a summary of introductory lectures of several courses on visual processing disorders, often called cortical or cerebral visual impairment (CVI). The concept CVI is mentioned only in this paragraph to clarify that we talk about the same group of functions and their losses as is covered by the concept CVI in the USA. The approach, however, is different. Instead of describing some general features in the functioning of severely multidisabled infants and children we will try to describe:

  1. the effect of lesions in the anterior visual pathways and refractive errors on the quality of visual information that flows into the brain for processing,

  2. the visual processing problems of children with intellectual disability as well as of children with normal or high intelligence and

  3. ocular motor functions that either support or disturb use of sensory functions.

An example:

If a child does not recognise family members, her therapist and teacher arrange the functional test situation when the medical services have first checked

  1. the need of spectacles,
  2. ocular motor functions and accommodation and then, using proper refractive correction and filters when needed
  3. measure visual acuity and contrast sensitivity with optotype and grating tests,
  4. colour vision,
  5. visual field and
  6. motion perception.

These measurements give information on the quality of visual information available for processing. If contrast sensitivity is very low and motion perception poor, low contrast features are not seen, except at close distances (that increase the size of the picture on the retina = geometric magnification). If a child with “mild” impairment of vision (i.e. visual acuity value is close to normal), does not seem to recognise family members, the family or the nursery school can arrange a test situation:

The therapist wears another person’s coat and a scarf, does not have her usual perfume, sits on a chair (because the way of moving could be facilitate recognition), and has a friendly smile. The child comes with an adult who asks “who has come to visit us” and the child can go close to her therapist to have an opportunity to see her face. If the child says: “I am Maya. What is your name?”, the therapist waits a moment giving the child more time to see her face before saying her name, at which time the child recognises the voice. The therapist then explains that she had borrowed another person’s coat because it was cold and it was therefore difficult to recognise her. The child learns that she uses clothing to recognise people and that this strategy may mislead sometimes.  

The suspicion on a loss of face recognition was confirmed, the child was made aware of his/her problem in a friendly way and with training on compensatory functions starting immediately. Such a finding should also lead to awareness of the child’s problem and restructuring play and communication situations so that the child can recognise each person by a specific detail.   

Most of the visual processing functions for education are observed in daily activities and communication situations. Therefore it is important that people, who care, train or teach children know what to observe, how to arrange test situations at school or kindergarten to confirm observations, and how to support the child in development of compensating strategies

In the assessment of visual functioning we follow the principles of the ‘International Classification of Functioning, Disability and Health, Children and Youth Version’ (2007), a WHO document that covers all areas in functioning in assessment, early intervention and education of children with special needs. It gives us a framework for working in collaboration between medicine, education and social services.

In the beginning it may look too difficult to have more than 70 to 80 different functions to think about but most of the functions to be observed and assessed are functions that are always examined as a part of the general developmental assessments. Now there is an added component to the vision rehabilitation teams, the questions: Does impaired vision affect this function? Which different ways can vision loss affect this function? How does the finding change my work, what should I do in a different way in therapies or teaching? To answer these questions we need to watch assessment and functioning of many children. Fortunately the work is not as difficult as it may sound; you will often experience that most of the functions of a child to be assessed are normal (see Figure 16).

The wide variation in the degree and number of impaired functions makes it usually impossible to assess and understand all functions during the first assessment even when there are available good reports from the earlier assessments and observations in the child’s daily functions. It is also difficult to remember all the functions that should be considered. Special schools and institutions have created lists and questionnaires of functions that should be always assessed, with details typical to the population they care for. When children with special needs are now integrated in local schools and infants with specific problems in early development of visual functioning have therapies by personnel with little or no prior experience of impaired vision, it becomes important to create a specific list of observations and measurements “done” and “to be done” when the infant or child has developed to the level where the function can be assessed. The list grows with the child and should be shared with all workers related to the care, education or social services so that each service has enough information to understand the decisions and methods of the other specialists.

As an example: it took several years of explaining that children with normal visual acuity and visual field could be severely visually impaired and disabled if contrast sensitivity was so poor that the child needed a video magnifier, CCTV for reading. Now we have an even more difficult situation if a child has normal values in all clinical tests but reads much better and with normal speed and reading time when using large magnification (although we have not been able to diagnose the cause) and due to mild finger ataxia cannot write so well that he could read his hand writing. It is difficult to find understanding for the recommendation of a CCTV and a laptop as devices for learning because “the child is not visually impaired and the cerebral palsy (CP) is very mild”. A person who has not observed the difference in reading and the difficulties in writing does understandably not grasp that the clinically measured values do not depict functioning of that child.

By recording the visual functioning of children well, the inclusion of vision care as an integral part of children’s general early intervention and education can be quite successful, especially if the special school for visually impaired children has a good resource centre with sufficient number of itinerary teachers and special materials.

The number of children with vision loss due to brain damage without other disabilities is small. A great majority of children with impaired vision due to brain damage has at least one additional problem, which is more visible than the visual impairment. The two large groups with “hidden” vision loss are children with developmental delay or intellectual disability (up to 50%) and children with motor problems, especially cerebral palsy (CP) (25 to 30%). Of the smaller groups of children with brain damage and vision loss, the very rare infants and children with dual sensory loss are the most difficult to understand if they have loss of all visual recognition functions (face, objects, pictures, landmarks; ventral stream functions), copying of facial expressions and hand movements (mirror neuron system functions) but normal vision for moving and eye-hand-coordination (dorsal stream functions) and simultaneously normal recognition of auditory environmental information but barely measurable functions in deciphering spoken language.

In the early intervention and education of multidisabled infants and children we often have to stretch our imagination to create activities and tasks that meet the needs of each child for further development. Rehabilitation becomes much like special education and special education is our important support in modifying the tasks to fit all the other problems of the child.


[ Instructions I Paediatric Vision Tests I Vision Tests ]

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