Vision in Early Development

Assessment of vision occurs several times during childhood, if the infant or child does not seem to use vision in an age appropriate way. Since there are so many different types of visual impairment this short text covers only some important features of assessment of the different groups of infants and children with low vision. I would like to stress three features in the assessment:

1. it covers all visual functions, form perception, colour perception and motion perception; not only visual acuity and the size of visual field.
2. its goal is a thorough evaluation of strengths and weaknesses in all functional areas so that special education and early intervention can be tailored to meet the needs of each child.
3. it is performed as a transdisciplinary activity.

In the assessment of adult persons and school children we can define four main functional areas where vision usually plays an important role (Hyvärinen 1985):

1. communication, both person-to-person, group communication and distance communication
2. orientation and mobility
3. activities and tasks of every day life (ADL)
4. sustained near vision tasks, like reading and writing.

In the assessment of infants each of these functional areas gets an additional feature: the role of vision in the development of each function, both at present and in learning the next level of functioning. The most important areas of development during the first year are:

• communication and interaction
• motor functions
• development of spatial concepts and orientation in space
• object permanence
• language development.

During the assessment we remember to ask ourselves:

1. What is the quality of the image that the infant/child uses?
2. How does the infant/child use visual information in the higher visual functions?
3. How do the impaired functions affect the development of the child?

Image quality

In the clinical assessment of impaired vision we usually measure grating or optotype acuity and visual field. Images have also other important qualities. We perceive:

• forms
• colours
• motion

Of these basic components of images colour perception and motion perception are functionally often more important than form perception, yet they are rarely measured as a part of functional assessment of low vision. Of form perception, usually only form vision at high contrast levels is measured with visual acuity tests. No wonder that the quality of image seen by a child or adult person with visual impairment so often is misunderstood.

Visual field needs to be measured, both its extent and, when the child is old enough, the structure of the visual field in detail. Visual adaptation is measured early in cases of retinal degenerations and oculomotor functions and eye-hand coordination assessed carefully. When a child has other impairments, their influence on use of vision and, vice versa, the effect of impaired vision on the other impairments, needs to be evaluated.

Assessment of young infants

In early interaction, bodily contact is central during the earliest weeks but then vision is the most important avenue in communication. A normally sighted infant expresses the joy she or he feels in communication; we understand the infant without any explanations (Figure 1.A). A visually impaired infant may not see enough to copy the smiles of the adult persons and therefore needs enforcement through tactile and auditory information (Figure 1.B). Since the visually impaired infant often has to concentrate on listening and does not have the usual eye contact, the infant is in danger of being thought to be uninterested in interaction.

The most important task in the assessment of infants is to find out how much vision there is for visual communication, whether

1. the infant uses central vision and thus has a possibility to have normal eye-contact or
2. uses an extrafoveal area of the retina to look straight ahead and seems to look past when looking at a persons face and
3. how close an adult needs to be to be seen by the infant.

Our expectations of the infant's responses are based on interaction with normally sighted infants and therefore it is difficult to accept and understand another type of response as a normal response in the case of visual impairment. The communication situation needs to be explained to the adult persons several times. Video recordings of early interaction are effective in demonstrating to the adult persons that the infant wants to communicate and enjoys interaction (Figure 1.).

Figure 1. Early interaction of a normally sighted infant and an infant with dual sensory impairment (visual and hearing impairment). A. At the age of three months, visual communication of a normally sighted infant is an effective bonding function; the infant and the adult person understand each other right from the start. B. A visually impaired infant may not have normal eye contact and may seem to look at the hair of the adult because of eccentric fixation. The infant uses tactile confirmation of auditory communication when lip movements cannot be seen. In such a situation the parents and caretakers need support and training in early interaction. (Pictures are from video recordings in the CD "LH-Materials for Teaching".)

If an infant has hypotonic accommodation (children with general hypotonia and some infants with Down Syndrome) or hyperopia, long-sightedness, the blurred image disturbs communication and therefore proper near correction lenses must be prescribed as soon as the difficulty in interaction becomes diagnosed, usually at the age of 3-4 months. If hyperopia is high, 6 dioptres or more, glasses are prescribed even earlier. A practical difficulty at that age is to find good spectacle frames that fit the small face.

Vision for motor development is the second most important aspect of the assessment. Reaching for objects and grasping, crawling toward an interesting toy and pulling oneself up to stand are all closely related to the development of spatial concepts of one's own body and of the surrounding environment. Therefore vision for development of spatial concepts needs to be assessed. Lack of detailed information on near space needs to be compensated by using playthings that give visual, tactile and auditory information (Hyvärinen 1998). Visually impaired infants often have motor impairments and thus get early motor training. Even infants without primary motor problems need guidance by an experienced therapist to avoid delays in their motor development. If the therapist has not previously taken care of visually impaired infants (s)he should get information and support from the early intervention team. The therapist is usually the person who works most closely with an infant and the family and learns to make important observations on the child's use of vision and changes in it.

During the first year, the number of tests is limited. At the beginning of an assessment we usually first observe how the infant looks around and whether (s)he has visual communication with the parents; then evaluate motor functions, fixation, tracking movements, convergence and saccades; binocularity by observing whether the eyes are looking at the same point in space (Hirshberg's test, cover test and Lang stereo test), visual field with confrontation tests and using ball games, visual acuity as grating acuity and contrast sensitivity with Hiding Heidi test.

Visual anticipation and the infant's ability to evaluate velocity can be assessed with the simple "castle" game where an interesting object moving at a certain speed is first shown to the infant, then it moves with the same speed behind a 10 cm "tower", becomes visible between the first and the second tower, disappears again and reappears between the second and the third tower. If the infant can correctly analyse the speed of the object and its direction of movement, the eyes move with correct speed to look at the object when it reappears (Figure 2.).

Figure 2. Infant's ability to anticipate the position of a moving object can be observed in this test situation where the object is shown and hidden in turn when moving behind the 'towers' of the 'castle'. The target has been moved behind the 'tower' and is just to appear. The infant has moved his eyes with the same speed that the target had when it was visible and thus his gaze is at the edge of castle simultaneously with the target (with permission from Prof. Francois Vital-Durand).

Infants usually copy facial expressions quite early and respond in a meaningful way to many expressions. If these responses are not present, either the infant does not see the expressions clearly enough (anterior visual impairment) or the cortical analytic functions or connections to memory have not developed. Toward the end of the first year it is possible to observe whether an infant recognises family members and responds to them differently from other persons. If an infant seems to have problems in recognition of facial features and/or expressions, specific communicative therapy is necessary to help the infant develop participation in social interactions.

Figure 3.This 4 month old infant was diagnosed as having infantile autism because she did not have normal eye contact with adult persons but seemed to 'avoid eye-contact'. The infant did not accommodate to usual fixation targets. Therefore we tried 'reading lenses', near correction, that gave her clear image on the retina from objects at near. The infant immediately looked surprised and after a few seconds developed a normal social smile and good eye-contact with her mother. Like many other infants who have difficulties in developing smooth accommodation she developed inward squint after a few weeks at a time when she started to accommodate.

Eye-hand-coordination can be assessed from the age of a few weeks when the infant first hits objects hanging within reach and then starts to reach for and to grasp them. Visually impaired infants use mouthing of objects later than normally sighted infants because their tongue and lips give more exact information about details than the blurred visual images do. Visuotactile materials are important in helping the infant to combine visual information with tactile and haptic information and should be available on loan if the family cannot afford to buy them.

During the evaluation one needs to constantly keep in mind that responses may be affected by either changes in the image quality or irregular visual associative functions or both. By using test materials of different sizes, colours and contrast, the role of the disorders of the eye on image quality can be assessed. Assessment of higher visual functions requires repeated observations by family members, therapists and early intervention specialists supported by the findings from the clinical examinations.

Assessment of toddlers

As soon as a child develops the concepts 'similar' and 'different' these concepts can be used to train for visual acuity tests. The test forms can first be matched based on their colours, then on their black-and-white three-dimensional forms (the LEA Puzzle), then comparing the forms and pictures of the same size and finally comparing either the puzzle pieces or the large pictures on the key card to smaller and smaller test pictures. When testing is possible using the high contrast pictures, low contrast pictures of the same test symbols can be used to measure form perception at lower contrast levels.

Binocularity tests like Worth 4-dot test become possible at the age of two years and stereo tests like the TNO slightly later. At this age, visual adaptation to lower light levels often becomes delayed in retinitis pigmentosa and can be tested with the CONE Adaptation test as the first sign of abnormal retinal function.

Children with suspected brain damage need a thorough evaluation because it is possible to measure crowding phenomenon and observe the child's ability to perceive size of objects, directions of lines and movement and to assess his/her eye-hand-coordination. Observation lists developed in Scotland by Gordon Dutton and in Nordic countries by Lena Jacobson and myself should be discussed with parents and day care personnel to learn about difficulties in the use of visual information. It is of utmost importance that communication difficulties are diagnosed and treated early so that the child can develop communication skills using compensatory techniques if (s)he is functionally blind in group communication. Too many of these children who do not recognise faces or expressions are diagnosed as autistic based on their failure to function in a group of children. Likewise it is important to understand the child's difficulties in spatial orientation or lack of perception of objects that stand still or those in motion. The observation list can be like the following:

Typical behaviours of children with problems in cognitive vision:

• Variation of visual functioning is the most common feature
• early development of speech as compensatory function
• the child prefers talking with an adult to playing in a group of children
• effective use of memory as compensatory function
• the child dislikes crowded places, clings there to the parents; beaches and swimming halls are worst if recognition of faces is difficult
• the child starts drawing and painting late
• colours are used for coding more than by normally sighted children
• little interest in TV and comic series
• the child may show signs of spatial interpretation problems, stops at thresholds and shadows
• the child may learn letters and numbers early but does not learn to read except short words
• the child uses siblings and adult persons as helpers when there is a demanding visual task
• the child may become angry when someone moves her/his playthings or clothes even minimally.

This same list of behaviours can be used through all preschool years. Milder difficulties in different visual perceptive functions become recognisable when the child grows and the demands on the different skills become greater. Since the number of children with brain damage related visual impairment is steadily growing, proper diagnostic skills need to be created for early diagnosis and intervention. Children with problems in motor development, children with intellectual disabilities and children who were born as small premature babies are groups that should be examined and observed particularly carefully. However, cognitive visual impairment may be present in children with no other problems in their development and may affect only one single perceptual function.

Assessment of school children

In many countries visually impaired children are in local mainstream schools where there is little knowledge about special learning techniques and how to teach them. Therefore the visual functions of the child should be described so clearly that the classroom teacher and the teacher's aid can understand them. It would be of great help if the functional assessments were to be carried out by the itinerant teacher during her/his visit at the local school. Most of the tests can be used after rather short period of training. Interpretation is sometimes difficult and requires analysis of the video made during the assessment by the diagnostic team responsible for the services.

During the assessment one needs to remember that responses may be affected by changes at three different levels of the visual system (Figure 4.):

1. in the eye and/or the anterior visual pathway,
2. in the pathway between lateral geniculate nucleus and/or the primary visual cortex and
3. in the cortical or subcortical brain functions.

Disorders of the anterior pathway affect the quality of the visual image, those in the posterior pathway cause visual field defects and increased crowding but may not damage the tectal pathway, which then transfers information to cortical functions bypassing the primary visual cortex and the usual form analysis. Disorders in the visual associative cortices are often patchy affecting specific visual subfunctions, recognition of persons by facial features, recognition of facial expressions, perception of objects on a patterned background, perception of size or directions, eye-hand coordination, orientation in egocentric and allocentric space, evaluation of surface qualities, place, movement and/or speed of objects.

Figure 4. Visual pathways have two major routes, the retinocalcarine pathway from the retina via the optic nerve (ON), optic chiasm (CH) and the lateral geniculate nucleus (LGN) to the primary visual cortex (called also calcarine cortex) and the tectal pathway via the superior colliculus (SC) and the pulvinar (P) to the associative cortices. Visual pathways transfer information through different neural pathways. The largest path (approximately 80% of the nerve fibres) is the parvocellular pathway that transfers all colour information and high contrast black and white information. Its nerve fibres are thin and transfer information relatively slowly. The magnocellular pathway (10% of the fibres) transfers all motion related information and low contrast black and white information. Its fibres are thick and have high speed of information transfer. From the primary visual cortex information flows into two main directions, toward the parietal lobe as the dorsal stream (DS) (the 'where' functions) and toward the temporal lobe as the ventral stream (VS) (the 'what' functions). There are effective feedback loops at all levels of the pathways; the visual pathways are 'two way streets'.

Before the functional assessment we need to collect all available information from the clinical examinations and laboratory tests. These are summarized by the ophthalmologist and the neurologist with special attention on findings in each of the three parts of the visual pathways. In some hospitals the clinical examination contains detailed description of oculomotor functions and most of the measurements of sensory functions required for functional assessment:

• visual acuity at distance with a single symbol test and with a line test,
• visual acuity at near with single, line and more tightly crowded test
• contrast sensitivity with a low contrast visual acuity test, possibly also with a grating test
• colour vision with a quantitative test
• visual field with confrontation, with Goldman perimetry and as the reading field
• visual adaptation to lower luminance levels.

Disorders of higher visual functions may not have been assessed before or were assessed more than a year ago, so the list of the typical behaviours is discussed with the parents and the day care personnel. Mild losses of function may not be detected before school age if the child has been in a small group of children with well-structured activities. Some children have developed effective compensatory strategies using siblings and adult persons as helpers in problematic situations. Specific problems in mathematics, reading and writing are often noticed first at school. The cognitive vision tests including observations on motion perception and spatial awareness complete the functional assessment. If the child makes errors in reading, testing with texts of different size reveals whether the errors are caused by small scotomas or distortions in the image. Thorough assessment of vision and hearing is always necessary when need of special education is considered.

What should the classroom teacher know about the child's visual functions?

1. Does the child have anterior visual impairment, posterior visual impairment or a combination of these two impairments?
2. Motor functions:
   • fixation, is it stable, too short or not present, central or eccentric; nystagmus with/without null position?
   • are the saccadic movements accurate; compensated with head movements?
   • how regular are the tracking movements; compensated with head movements?
   • are there any involuntary eye movements during spasms or epileptic activity?
3. Sensory functions:
   • visual acuity, all 4-5 measures with optotypes; smallest and optimal text size
   • contrast sensitivity, at least visual acuity at 2.5% contrast
   • colour vision, confusion areas, which colours need to be avoided
   • visual field for orientation and for reading
   • visual adaptation, speed of adaptation, any effect on walking to school in twilight; can the child go out during breaks on sunny days when using his absorptive lenses?
   • does the child recognise people by their facial features, if not which compensatory techniques have been used for recognition?
   • does the child see expressions?
   • motion perception; does the child see objects that stand still as well as those moving?
   • does the child perceive size, length or does (s)he need haptic confirmation?
   • does the child see directions of lines?
   • does the child see details in pictures with many details?
   • can the child play with age appropriate puzzles?
   • eye-hand coordination, use of pencil and pen, drawing
4. Vision for orientation and mobility, what needs to be considered in physical training?
5. What kind of vision the child has for sustained near work? Glasses, devices. Motivation and skills to use them; new devices to be considered during the term?
6. Illumination at the desk and the black board, in the classroom and the corridors.
7. Which devices should the school purchase, which come from other sources?
8. Does the child have symmetric, normal hearing? Any other functional difficulties, disorders or diseases that might affect functioning at school?
9. Prognosis: stable or progressive condition.

This information is given to the classroom teacher and the child's assistant and therapist and discussed again after a few weeks when the child has become accustomed to the new school situation. When the tests are made at the school in the presence of the teacher and the assistant they understand the test results much better than if the results were only described. They can repeat some tests later and make observations that they report to the child's family doctor and to the intervention team.

Since the tests can be used by all personnel categories, the assessment becomes a true transdisciplinary activity. In the beginning it often requires assurance by the ophthalmologist or by the psychologist because it is quite deep rooted a belief that only doctors or psychologists may use vision tests. The child's teacher and assistant need the information on the child's strengths and problems in learning more than anyone else and thus are usually motivated to take care of the repeated assessments, especially visual functioning related to reading. In interpretation of observations they need help by special teachers who are experienced in assessing visually impaired children with other impairments.

When a child's functional situation is described, all major functional areas need to be described: how much vision there is for

1. communication,
2. orientation and mobility,
3. activities of daily life and
4. sustained near vision tasks.

In each of these four functional areas the child may use either techniques typical to blind persons, techniques typical to persons with low vision or techniques typical to normally sighted persons. If the techniques of blind persons are given 3 points, low vision techniques 2 points and techniques of normally sighted 1 point, we have a variation between 12 and 4 points, which is large enough a range for administrative purposes. However, it should be explained that there may be variation in each of the functions at varying luminance levels (Table 1.)

Table.1. This graphic way of describing visual functions of a child with visual impairment is often best understood by administrative persons. It also clearly shows which kind of services the child needs and where special techniques need to be taught. This child has retinitis pigmentosa and must use techniques typical to blind people when the luminance level is low, like when coming to school early in the morning or when working in a poorly illuminated corner of a classroom. Yet when he is reading at his desk he uses techniques typical to his normally sighted classmates, except when looking for something under the desk. (From Hyvärinen L: Assessment of Vision for Educational Purposes and Early Intervention, Part I)

( In the German text the students preferred following table with similar content. You will find out which way of describing the situation works best in your case.)

Functional assessment is based on thorough clinical examination including measurement of refractive error, prescription of glasses (and explanation whether they under- or overcorrect the refractive error and if so, why), description of the structure of the eyes and optic pathways and what changes in them may mean to the use of vision (MRI, Ct, VEP when available). Combined with observations during school and recreational activities they help us to understand a child's strengths and weaknesses and help us to choose proper teaching techniques.

Whenever there is a discrepancy between clinical findings and a child's behaviour all tests need to be repeated at school and reported to the child's ophthalmologist and neurologist so that the need of further clinical examinations can be evaluated. Some present clinical findings do not depict functional vision and thus observations are important at school, at home and during recreational activities.

Low vision may improve during the early years at school if it is not caused by a progressive disorder. Follow-up of the progression of the disability (or as the new ICIDH describes it, 'how much the disorder affects activities') and the development of compensatory skills becomes well structured if each of the functional areas is assessed in detail (Table 2. see PDF-file below). This table needs to be modified to adapt to each child's functional profile, environment and cultural background. In the left column one writes down the degree of effect of the disorder on the function and in the right side the level of developing compensatory functions. The former often changes little; the latter should improve if teaching meets the needs of the child.

References:
Hyvärinen L (1985) Classification of visual impairment and disability Bull Soc belge Ophtal, 215, 1-16.
Hyvärinen L (1998) Home page at http://med-aapos.bu.edu/leaweb/index.html
Hyvärinen L (1998) Home page at http://www.lea-test.fi
Hyvärinen L (2000) "LH-Materials for Teaching", CD, Lea-Test Ltd, Helsinki

Authors address: Lea-Test Ltd, Apollonkatu 6 A 4, FIN-00100 Helsinki
e-mail: lea.hyvarinen@lea-test.fi