Introduction to Testing Cognitive Vision

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:

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.

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.