The patients, suffering from an inherited form of blindness called retinitis pigmentosa, experienced "useful vision" -- able to distinguish black from white and see the rough outlines of objects -- just weeks after having a light-sensitive microchip inserted into the back of their eye, The Daily Telegraph reported Thursday.
After years of total blindness the brain needs to "relearn" how to process vision, doctors said, raising hopes the patients' vision may undergo further improvement.
The implant is placed underneath the retina and the eye's natural focusing power transmits light to it, then the implant uses its 1,500 electrodes to convert light into electrical impulses which are sent up the optic nerve to the brain.
"You can think of the retina as the film in the back of a camera," Tim Jackson, a consultant retinal surgeon at King's College Hospital and one of the trial leaders, said.
"That has died away but the remaining connections are still intact and we can use these to transmit a signal to the brain. The chip replicates the action of the cells that have died away."
Robin Millar, 60, from London, is one of the patients who received the retinal implant.
"Since switching on the device I am able to detect light and distinguish the outlines of certain objects which is an encouraging sign," he said.
"I have even dreamt in very vivid color for the first time in 25 years so a part of my brain which had gone to sleep has woken up."