For a man whose view of the world has slowly faded to black over 30 years, a device that allows him to see flashes of light has kindled his hope of one day gazing upon his grandson's face. A career electrician who grew up in Greece and came to the US as a young man, Elias Konstantopoulos first noticed his vision getting poorer when at age 43 he absentmindedly tried on a relative's eyeglasses and found he could see more clearly with them than without.

Soon after, he visited a doctor who tested his sight and discovered he was no longer able to see his outstretched arms from the corners of his eyes. His peripheral vision was deteriorating . He was diagnosed with an incurable condition known as retinitis pigmentosa, which affects 100,000 people, or one in 3,000, in the US.

A leading form of hereditary blindness, the disease gradually eats away at the retina's rods and cones, which are photoreceptors that help people see light and identify color and detail. About 10 years later, he could no longer see well enough to keep working. "You lose your sight, you pretty much lose everything," said Konstantopoulos, who is now 72 and lost his final bit of vision about five years ago.

When his doctor asked in 2009 if he would like to join a three-year trial of a futuristic technology involving an electrode array in his eye and a wireless camera mounted on a pair of glasses, Konstantopoulos was eager to take part.

Now, every morning he puts on the glasses, straps a wireless device to his waist and stands by the window or out in the yard waiting to hear the sound of a car approaching . When it passes, he says he can see a block of light go by.

He can also distinguish light-colored objects against dark backgrounds, and he can orient himself in a room by being able to see where there is an window letting the sun in from outside . The device, known as the Argus II, is made by a California company called Second Sight. It was approved for use in Europe, and in the US it has given a handful of test patients like Konstantopoulos cause for optimism.