John Brigande, who hears nothing out of his left ear and only poorly out of his right, has revealed that his experimental gene therapy has been found to generate the type of cells that are damaged or missing in deaf animals.

He revealed that when mice embryos were injected with a key developmental gene during a study, it led to the production of ear cells that convey sounds to the brain.

"That is sort of the major achievement or milestone that we all had to reach," New Scientist magazine quoted Stanford University cell biologist Stefan Heller, who was not involved in the study, as saying.

Brigande, however, insists that his advance represents only an incremental step in the search for a treatment to human hearing loss.

"We're really far away from a cure for deafness," says Brigande, who began losing his own hearing aged 10.

While speaking to the magazine with the aid of a closed captioning program, he said: "I'd like to hear, and I would love to be a member of the research team or community that does define an efficacious therapy, but I think it needs to be approached with enormous caution."