Cognitive Abilities of Children with Down's syndrome – Delayed or Different?

There are much better informed sources of information about cognition in Down's syndrome than ours, since our expertise lies in vision. However, we are willing to share what little we know. Much of the research into the cognitive abilities of children with Down's syndrome suggests that their development follows a similar route to that of typically developing children but that these developments are delayed. Unlike their typically developing peers, children with Down's syndrome do not seem to have a constant trajectory of development. The rate of development, as measured by IQ, seems to become progressively slower over time and it is presently unclear exactly when this deceleration rate of development ends. Researchers who have studied the development of these children in greater detail and over long periods of time report that development is actually different as well as delayed.

Visual Defects Affecting School Performance

Visual defects in children with learning disabilities are often not picked up, as it is assumed that any difficulties in learning or behaviour are due to the learning disability. It is therefore important that parents, teachers and other professional are aware of the types of behaviour or difficulties that may be associated with visual problems.

Teachers are in a good position to identify any visual problems if they know what they are looking for. Physical signs (irritated eyes, screwing up their eyes, and frequent blinking) along with behaviours (poor concentration, distractibility, clumsiness) are indicators of possible visual problems.

Visual skills such as distance acuity, near acuity, eye movement control, near point convergence (movement of eyes in towards the nose), stereopsis (binocular vision), colour awareness and posture are all needed for classroom tasks. Even children who appear to be adjusting typically to the school environment may have visual problems, which are keeping them from reaching their full potential. Since we know that visual problems are common in Down's syndrome, teachers should encourage parents to take up any opportunities for full eye examinations.

Distance Acuity

This is the ability to see fine detail at a distance.

Studies have shown that children with Down's syndrome have reduced acuity (detailed vision) compared with their typically developing peers, even when significant long or short sight is corrected with glasses. Teachers need to be aware of this so that suitable provisions can be made. Uncorrected long or short sight and eye conditions like nystagmus reduce vision further.

Possible remediations:

• Move child's desk, or seat closer to the board
• Write larger on the board or change the colour of marker used – increase the contrast i.e. black on white / white on black
• Reduce amount of copying from the board and provide material at the desk

Nystagmus

Nystagmus is a continual, regular, but uncontrollable movement of the eyes that is far more common in children with Down's syndrome than typical children. However, it is not part of the syndrome and represents a visually impairing condition in addition to any learning disability.

The following behaviours are common among children with nystagmus :

• The child may adopt an unusual head position (known as the 'null' position) – as this is a point where the movement is least and thus vision is best
• Lack of concentration especially when tasks are complex or long
• Becomes increasingly tired or disruptive as level of work intensifies, and usually becomes worse towards the end of the day

Possible remediations:

• Encourage the child to find the best head position which allows them the least amount of visual disturbance
• Position the child in the classroom to accommodate the child's head turn
• Allow the child additional time for completing written tasks as scanning is difficult
• Allow the child to copy information from worksheets in front of them rather than from the board
• The amount of detail a child can see is reduced so increase size and contrast of text. Reduce visual distractions from worksheets.

Near Acuity

This is the ability to see objects that are within 18 inches of the face.

Children's near vision is going to be reduced in the same way as their distance vision. In addition, children with Down's syndrome often have difficulty in focusing well so near tasks are even more blurred than distance. Contrast sensitivity is also poorer in Down's syndrome, and some near tasks are quite low contrast (writing in pencil, faint lines on a page) and therefore difficult for a child to see. Many children with Down's syndrome experience difficulty in keeping written work on the lines provided and this has often been considered due to 'poor fine motor control'. In fact, it is more likely to be because the child cannot see the lines.

Possible remediations:

• Provide worksheets/books with larger print and increased contrast
• Ensure that lines are bold and clear by going over them with black pen
• Allow the child to write in pen
• Reduce the amount of information on a page/worksheet

Colour Awareness

This is the ability to discriminate between colours.

Children with Down's syndrome are no more likely than typical children to have colour defects. However, 8% of all boys have a colour defect (and only 0.2% of girls). Children with Down's syndrome will find discriminating subtle shades of colour more difficult, because of poor contrast sensitivity.

Possible remediations:

• Be aware that the child may not see coloured print in textbooks as easily as typical children
• Ensure that colour coding involves bright colours

Communicating With Other Professionals

If a child in your class has visual difficulties it is important that you know how any visual problems will affect school work and how to manage any difficulties. If glasses have been prescribed you need to know what they have been prescribed for, and when they should be worn. Most eye care practitioners will be happy to produce a written report for teachers, but you may need to request one.

Your authority's VI service will be available for general advice, and, of course, the school can refer any child with visual problems to the service, although the criterion for referral may vary between authorities.