American doctors have implanted three more microscopic chips in the eyeballs of men suffering from retinal damage in the second phase of a study to determine whether the chips can restore human vision.
The operations are part of a clinical study aimed at reversing blindness caused by retinitis pigmentosa, a hereditary condition that gradually degenerates the retina.
Ophthalmologist Alan Chow, who led a team of four surgeons performing the implants, said in a statement that results from surgeries won't be revealed for several months until the US Food and Drug Administration has had time to review data from the trial.
The microchips used in the 2.5-hour surgery are smaller than the head of a pin and about half the thickness of a sheet of paper.
Two of the surgeries were performed at Central DuPage Hospital in Winfield, Illinois, and the third at Chicago's Rush-Presbyterian St. Luke's Hospital.
The first phase of the study began a year ago with two men and one woman who were implanted with the Artificial Silicon Retina chip, created by the Illinois-based Optobionics Corporation.
The chip is powered by solar cells that convert light into electrical impulses. The chips replace damaged photoreceptors, which sense light, and also help stimulate the remaining healthy retinal cells.
Loss of photoreceptor cells occurs in retinitis pigmentosa and macular degeneration, the two most common causes of untreatable blindness in developed countries, affecting at least 20 million people worldwide.
