From Darkness to Light: Giving Sight to the Blind
Blindness -- once relatively ignored by research scientists -- has in recent years received greater attention and increased funding, all driven by expectations of increasing numbers of cases of blindness in an aging population.
Around the world, "bionic eyes" are under development.
Last summer, Hessburg headed an international symposium that brought together 20 of the world's leading researchers working on these inventions. The majority, he tells WebMD, are focused on developing intraocular retinal implants -- small microprocessor chips embedded in the eye, which send a message through the optic nerve to the brain.
One group of researchers at the Wilmer Eye Institute at Johns Hopkins Medical Center in Baltimore has paired a tiny television camera with something called an ultrasonic distance sensor (mounted on a pair of eyeglasses). The glasses send the signal to the sensor, which sends a signal to a microcomputer chip embedded on top of the retina -- which transmits signals to the brain's visual cortex, the area of the brain that controls vision, explains Giflin Dagnelie, PhD, assistant professor of ophthalmology at John Hopkins Medical School in Baltimore.
When the camera sends a video signal to the small processor, the image is streamlined, says Dagnelie. "It basically pares the image down to the most important components, like edges and contrast -- so a person can see the outlines of a face, see a doorway, obstacles in their path, things like that. We think it will be a while before it's good enough that they can recognize faces with this, but they will be able to distinguish faces."
In preliminary tests involving six patients -- performed under local anesthesia, so patients could report what they were seeing -- Dagnelie and colleagues first showed them one or two dots, then as many as 25 dots in a 5- by 5-inch square, then one letter at a time," he tells WebMD. The images they see are very crude, he adds. "Think of this as a stadium scoreboard, but just a tiny little corner of it made up of big crude dots. It corresponds to about 20/2000 vision -- really primitive."