The sight of two blind people has been partially restored after surgeons at a leading UK hospital fitted them with "bionic eyes".

The operations, carried out at Moorfields eye hospital in London, give new hope to sufferers of a hereditary disease of the retina that causes progressive and severe blindness.

The groundbreaking surgery is part of a clinical study to test the effectiveness of the artificial retinal devices in treating retinitis pigmentosa (RP), a group of inherited eye diseases in which there is gradual deterioration of the light-sensitive cells of the retina.

The implant gives severe RP sufferers a basic level of useful vision, in the form of spots of light and shapes of light and dark.

The technology consists of a tiny camera and transmitter mounted in a pair of glasses. The camera transmits a wireless signal to an ultra-thin electronic receiver and electrode panel implanted in the eye and attached to the retina.

The electrodes stimulate the remaining retinal nerves, which send a signal along the optic nerve to the brain.

The brain perceives patterns of light and dark spots corresponding to the electrodes that are stimulated.

The operations were done by a consultant retinal surgeon, Lyndon da Cruz, and his team under the supervision of colleagues in the US who developed the device with the American company Second Sight.

Cruz said Moorfields was one of three sites in Europe chosen for the trial. "The devices were implanted successfully in both patients and they are recovering well from the operations," he said.

"It is very special to be part of a programme developing a totally new type of treatment for patients who would otherwise have no chance of visual improvement."

David Head, the chief executive of the British Retinitis Pigmentosa Society (BRPS), said: "These are significant advances and, in conjunction with the advances being made in stem cell therapy and gene therapy, make for really exciting times as we work to translate science into treatment.

"I'm encouraged and cautiously optimistic that treatments are perhaps being developed in a time scale that is meaningful for people who have retinitis pigmentosa now.

"The society has been fighting RP for 32 years and there's no doubt these are some of the most promising developments we have seen."

Professor John Marshall of St Thomas' hospital London, who is chairman of the BRPS medical advisory board, said the surgery was still in its "very early days".

"It is very, very good news that devices have been developed, it is very good news that in experimental trials some individuals have had these inserted.

"However, the general public should not run away with the idea that this is going to be routine surgery for blind people in the immediate future because there is an enormous amount to learn."