Bionic eye could restore sight to millions of blind people.
Scientists have developed an implant, which delivers long pulses of electrical current in people blinded by a rare condition in which photoreceptor cells gradually cease to work.
The device improves image sharpness.
Retinitis pigmentosa is a rare hereditary condition that causes gradual deterioration of the light-detecting cells in the retina, which can lead to blindness.
Current artificial retinas give patients the ability to perceive light using a camera mounted on a pair of glasses, a video processing unit that transforms images into wirelessly transmitted electronic signals and an implanted array of electrodes to stimulate visual neurons.
They have enabled blind individuals to detect motion and locate large objects but because the devices could unintentionally stimulate nerve cells in the retina patients sometimes see large oblong shapes of light that reduce the quality of vision.
They stimulate the retina with brief pulses of electrical current roughly 0.5 milliseconds in duration.
Problems start in the teens with the peripheral vision and problems seeing in low-light conditions and by middle age vision problems become greater and some will become blind.