The vision development of more than 400 children aged three-and-a-half was studied by a team at Bristol University as part of a project which has been monitoring the progress of 14,000 children since 1991. Researchers found that children whose mothers ate oily fish during pregnancy reached good depth perception sooner. Oily fish contain what is thought to be the richest dietary source of DHA, a fatty acid which is an essential building block of nerve cell membranes in the brain. The vision of children who were breastfed also developed faster than normal, since breast milk also contains DHA. The project's ophthalmologist Dr Cathy Williams said: 'As far as we know, this is the first time that diet in pregnancy has been shown to be associated with a child's visual development.'