Duke Medicine. Larry Hester and Paul Hahn beam as Hester is able to see light for the first time in 30 years

The first bionic eyes are giving vision to people who have been blind for decades. While recipients remain legally blind, it can still be transformative for the recipient's lives. Moreover, the technology is expected to improve rapidly.

For Larry Hester, one of America's first bionic eye recipients, the implant so far only allows him to distinguish between light and dark. Yet this video makes clear just what it means to him and his family.

The Argus II Retinal Prosthesis Device Hester received is the product of research at the Duke Eye Center, where the operation was done, and developed by spinoff company Second Sight Medical Products. It received US commercial approval last year, following successful trials on 30 subjects. Alternative versions are in clinical trials around the world.

Bionic eyes work on a similar principle to cochlear implants. Light is detected by a camera, which converts it to an electrical signal. Where the bionic ear's electronics plug into the scala tympani the eye has a retinal implant with 60 electrodes that link to optic nerve for transmission to the brain.

The best vision achieved in trials of the Angus II was 20/1620, well below the threshold for legal blindness. However, the first bionic ears were pretty limited affairs as well.

The Argus II is designed for patients with retinal degeneration, most commonly retinitis pigmentosa, a genetic disease affecting 1.5 million people worldwide. Unlike damage to the cornea, retinal conditions like this have not previously been able to be treated.