The technology could one day be used to restore sight to wounded soldiers and patients with advanced forms of diabetes and glaucoma.
Affected by a degenerative condition known as retinitis pigmentosa, Allen Zderad was effectively blind, unable to see anything but a bright light. As the condition has no cure, Zderad, from Minneapolis-Saint Paul, MN, was forced to quit his professional career.
He made adjustments to his lifestyle and was able to continue woodworking through his sense of touch and spatial awareness. However, with the help of his new retinal prosthesis, Zderad is now able to make out the outlines of objects and people, and could even register his reflection in a window.
"I would like to say I think he's a remarkable man, when you consider what he's overcome in dealing with his visual disability," says Dr. Raymond Iezzi Jr., an ophthalmologist from the Mayo Clinic. "To be able to have offered him the retinal prosthesis to enhance what he can already do was a great honor for me."
Retinitis pigmentosa is an inherited condition that causes the degeneration of specific cells in the retina called photoreceptors. The disease can cause some people to lose their entire vision. Mr. Zderad's grandson has the disease in its early stages and, after seeing him, Dr. Iezzi asked if he could meet his grandfather.
The eye implant that Zderad now has works by bypassing the damaged retina and sending light wave signals directly to the optic nerve. A small chip was attached to the back of the eye with multiple electrodes offering 60 points of stimulation.
'Not like any form of vision that he's had before'
Wires from the device on the retinal surface connect to a pair of glasses worn by Mr. Zderad. The glasses have a camera at the bridge of the nose that relay images to a small computer worn in a belt pack. These images are then processed and transmitted as visual information to the implant which in turn interprets them, passing them on to the retina and eventually the brain.
"Mr. Zderad is experiencing what we call artificial vision," explains Dr. Iezzi. "It's not like any form of vision that he's had before. He's receiving pulses of electrical signal that are going on to his retina and those are producing small flashes of light called electro-phosphenes. These small flashes of light are sort of like the points of light on a scoreboard at a baseball game."
There are only 60 of these flashes of light, but it is enough for Zderad to reconstruct scenes and objects. Although he will not be able to see the details of faces or read, Mr. Zderad will now be able to navigate through crowded environments without the use of a cane, significantly improving his quality of life.
"In addition, while Mr. Zderad has 60 points of stimulation, if we were able to increase that number to several hundred points of stimulation, I think we could extend the technology so that patients could recognize faces and perhaps even read," he concludes.
"It's crude, but it's significant," said Zderad happily, as he first used the device. "It'll work."
Zderad will now be able to see his family again, including his 10 grandchildren and his wife, Carmen. And how does he distinguish her, having not seen her for a decade? "It's easy," says Zderad, "she's the most beautiful one in the room."
At the end of last year, Medical News Today reported on the story of a woman with quadriplegia who is now able to use her mind to move a robotic arm, demonstrating "10° brain control" of the prosthetic.