The US Food and Drug Administration (FDA) has given the go-ahead for the controversial transplant of embryonic stem cells into the eyes of patients with Stargardt's macular degeneration, where the light-sensitive retina cells at the back of eye are destroyed. The announcement follows the first injection of embryonic stem cells into a patient in the US who is partially paralysed as a result of a spinal cord injury. Last October, a US biotechnology company, Geron, announced the start of the first clinical trial of embryonic stem cells with the hope of repairing damaged nerves.