Discovering the causes of vision impairment in Down's syndrome children is the aim of a Pounds 195,000 Medical Research Council-funded project under way at Cardiff University's department of optometry and vision sciences.
"Three-quarters of Down's children develop vision defects at a very early age," says project leader Margaret Woodhouse. "They become short-sighted or long-sighted at the age of two - substantially earlier than normal children, who tend to develop such problems in late childhood or the early teenage years."
Interestingly, a pilot study with 54 Down's syndrome children at the department revealed that their vision is good until their second birthday. This study, financed by the Down's Syndrome Association, also shows that until this age Down's children develop cognitively in the same way as their normal peers. The only difference seems to be that they start talking, and walking, and achieving other milestones later than their peers.
But around their second birthday they start falling significantly behind.
So the key to Dr Woodhouse's research is finding why this is so, and then developing ways of treating and hopefully preventing deterioration.
"There are two hypotheses," she says. "Either the children slow down because they cannot see or the ingredient which causes the visual defect is the same as the one that impairs cognitive development."
To find out which is correct she will be following 25 Down's children as they reach their critical second brithday.
She will also consider prevention strategies such as prescribing glasses at 18 months or stimulating the children to make the best use of their existing vision. There will also be biochemical investigations into the mechanical causes of the childrens' eye defects.
According to Dr Woodhouse, the findings will be significant for other children with learning difficulties, such as cerebral palsy patients as well as Down's children. They too are prone to early vision defects.
She recognises that three years - the length of the MRC project will be insufficient to discover all the answers but much will be done during this first study of its kind to find out the relationship between defective vision and learning difficulties.
The research will be undertaken in partnership with the Welsh Centre for Learning Disability based at the University of Wales College of Medicine.
The project will also be able to recruit two specialist researchers, as the MRC grant will finance the appointment of an optometrist and a psychologist.