Blue eyes are caused by a gene mutation. For years, researchers had searched for it on the OCA2 gene. The OCA2 gene determines how much brown pigment is in our eyes. But what they were looking for ...

These children were each treated in one eye. After the researchers saw the treatment was safe and seemed to be working, they gave the gene therapy in both eyes of a further seven children.

n a Phase 3 gene therapy trial intended to improve vision among patients with Leber hereditary optic neuropathy, recipients gained somewhat better sight in both eyes even though only one was treated.