How the stem cell operation works

Doctors at Moorfields Eye hospital in London have been given the go-ahead to carry out Europe's first clinical trial using human embryonic stem cells.

They will inject retinal cells into the eyes of 12 patients with an incurable disease, Stargardt's macular dystrophy, which causes progressive sight loss.

The trial will test the safety of using replacement retinal cells known as retinal pigment epithelial cells, derived from human embryonic stem cells.

The trial is a partnership with an American bio-tech company Advanced Cell Technology (ACT) which has already begun treating patients in California.

Prof James Bainbridge from Moorfields Eye Hospital explains the procedure.

Surgery footage courtesy of Advanced Cell Technology.

How the stem cell therapy works