Ocular Morphology

From previous published reports, we knew that the retina (the layer at the back of the eye) looks different in people with Down's syndrome and ordinary people. In Down's syndrome, there appear to be more blood vessels on the surface of the retina, and the optic disc (where the nerves leave the eye to travel to the brain) has been described as 'rosier'.

Ping Ji decided to measure and catalogue these differences by taking fundus photographs in children with Down's syndrome and typical children, and analyse the size and shape of the optic disc and the numbers and arrangement of blood vessels.

Optic nerves

Because children with Down's syndrome have slightly poorer vision than typical children, we expected to find that the optic disc is smaller in Down's syndrome. Forty-five children with Down's syndrome and 44 typical children took part.The analysis isn't fully completed yet, but Ping has found, quite unexpectedly, that children with Down's syndrome have larger optic discs. Further, other dimensions of the retina appear larger, as if the retina is stretched. But the children's eyes are not stretched overall, because Ping has measured the length of the eyes and matched the children with Down's syndrome with typical children of exactly the same eye length. At the moment, Ping's findings represent a mystery.

Retinal blood vessels

Ping's photographs show that children with Down's syndrome do indeed have more blood vessels. This is because the same number of vessels enter the eye, but they then branch out more often over the retina than do typical children's.

Cornea

Ping also took measures of the dimensions of the cornea and front of the eye (anterior chamber) in the children. When we have completed this analysis, we will have a better idea of the size and shape of the eye in children with Down's syndrome, and whether the differences might explain some of the defects the children's eyes develop.