Defective genes may be to blame for the rare condition that caused Brighton model Jordan's two-month-old son Harvey to be born blind, say researchers.
Previously, it had been thought genes did not play an important role in septo-optic dysplasia (SOD), which damages the optic nerve.
Instead, the condition was linked to environmental factors, possibly including alcohol or drugs.
But British scientists have identified a mutant gene called HESXI, common to a few cases of SOD.
Mehul Dattani, of Great Ormond Street Hospital for children in London, said: "There is no hard evidence to suggest alcohol and drugs is the cause of blindness or that the condition is commoner in younger mothers.
"The research we are conducting into the role of genes in causing this disorder should enable us to develop a better understanding of it."
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