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The need for optometric services

Children with Down's syndrome are much more likely to have eye and vision disorders than other people do.

Our study unit was first set-up in 1992-1993 to determine the prevalence and age of onset of the defects that we were seeing clinically. In particular, we were (and remain) interested in the number of children with Down's syndrome who appeared to under-accommodate for near targets.

We now have considerable data on the ways in which eyes and vision develop in young children with Down's syndrome so that eye-care practitioners can be better informed when making clinical decisions about managing children's eye-care.

Overall, we find the prevalence of 'Optometric defects' to be as follows:

Defect

Controls

Down's syndrome

Myopia/Hypermetropia

4.5%

42%

Astigmatism

7.7%

28%

Poor accommodation

0%

76%

Strabismus

4-7.5%

29%

Below-normal acuity

0%

100%

The birth-rate of children with Down's syndrome is around 1 per 1000. Around 60% of the children are boys, and over 50% have congenital heart defects (although not all life-threatening). Advances in medical care for heart conditions means many more children survive to adulthood, so the prevalence of the condition is increasing.

The defects can arise throughout childhood and therefore children with Down's syndrome should be encouraged to have regular eye examinations whatever their age. If any abnormalities are found then subsequent examinations may need to be more frequent.

Regular eye examinations from an early age

< two years old – three to six monthly intervals

> two years old – six monthly intervals

> five years old – yearly intervals (if refractive error has stabilised)

Generally, the same techniques as are used with typically developing children are equally applicable to children with Down's syndrome. Because of the learning disability associated with Down's syndrome, techniques designed for a younger age may be more suitable. All children with Down's syndrome are individuals and many are very able, so avoid automatic assumptions about which tests to employ.

As for all children, have a wide variety of tests available, and adopt a flexible approach to avoid boredom. Good communication is essential, as it is for all patients. On the whole, children with Down's syndrome do better at understanding the spoken word than they do at speaking themselves. So don't under-estimate a child's ability if he or she cannot talk to you. On the other hand, many children have hearing deficits and their auditory processing is slow, so you will need to speak a little more slowly than usual and in shorter sentences. Give any patient with Down's syndrome longer to respond to your question or instruction. If you try to rush your patient you will only end up confusing or frightening them.

Many children with Down's syndrome find it disturbing to 'fail' and are, therefore reluctant to try when tasks become difficult. When doing a visual acuity test, for example, a child may begin enthusiastically but get distracted and lose interest when the smaller targets are presented. You will get the best out of a child with Down's syndrome if you avoid reinforcing 'failure'. Try interspersing difficult targets with easy ones, give lots of praise and encouragement, and always end the procedure with a success.