15 September 2013 Last updated at 20:11 ET By James Gallagher Health and science reporter, BBC News
A blood test that may improve treatment for children born with congenital cataracts has been developed by researchers in Manchester.
It analyses every known mutation in the DNA which can cause the condition.
The team, which is presenting the test at the British Society for Genetic Medicine, hope it will spread up diagnosis and help decide the best treatment.
The charity RNIB described the test as a "welcome step forward".
About 200 children are born with cataracts in the UK each year.
"Diagnosing a congenital cataract is very easy at birth, but diagnosing the cause takes considerably longer," Prof Graeme Black, from the University of Manchester, said.
The problem is there are more than 100 different mutations in a child's DNA which have been linked to congenital cataracts.
"If you have a child with no family history then finding the cause can take months or years," he told the BBC.
A complete diagnosis can help doctors work out the best course of treatment, inform families on the risks of cataracts if they have more children or diagnose severe diseases which have cataracts as an early symptom.
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Child cataract blood test developed