Science Sets Sights On Artificial Vision Different Implant Device Ideas Reflect Two Schools Of Thought

Mrs. Brown was nervous.

Eugene de Juan was just about to pull her right eyelid up with clamps, poke a hole through her eye with a mean-looking tool and then send bolts of electricity hurtling into the retina of the 64-year-old North Carolinian.

Lying under a surgical sheet, surrounded by tubes and dials and meters, by blinking machines that beeped in rhythm with her heart and operating lights that shone in her face, she confessed her fears.

De Juan, a surgeon at Johns Hopkins School of Medicine here, looked puzzled. “What exactly are you nervous about?” he asked.

To de Juan, the equipment that looks ominous to Brown is part of a scientific quest, the search for artificial sight. Despite her last-minute nerves, Brown, who has almost no central vision, is willingly part of that quest.

Along with dozens of scientists and engineers across the country, Brown and de Juan are probing the mysteries of sight in order to accomplish the amazing. They want to get the blind to see. And they think electronics can show the way.

The purpose of the experiment on Brown, who would not give her first name, was to understand how electrical signals given to the retina translate into the perception of light. Building on this knowledge, scientists eventually hope to implant electrodes at the retina, or even in the brain, to do the work our eyes do.

While this isn’t the stuff of miracles, within about a dozen years it could benefit hundreds of thousands of people with severely impaired vision.

“They will have a visual sense that will be vastly inferior to normal vision, but vastly superior to being blind,” said Richard A. Norman, a scientist at the University of Utah in Salt Lake City.

Some 100,000 Americans are either completely blind or can only distinguish between light and darkness. Some 600,000 to 900,000 people have sight so diminished they are declared legally blind. And 3 million others have low vision, chronic conditions that cannot be corrected with glasses or contact lenses, according to the federal government.

The leading causes of vision deterioration are cataracts, macular degeneration - the deterioration of the crucial middle portion of the retina - and diabetic retinopathy. In diabetic retinopathy, blood hemorrhages in the eye obstruct vision or destroy the retina, the sensitive tissue at the back of the eye that has the crucial cells that respond to light.

All these conditions affect the eyes. Since the central organ of human vision is the brain, these scientists reason if they can somehow “bypass” the eye’s normal function and get a visual signal directly to the brain, the person will be able to “see.”

It’s easier said than done, of course. The eye is an amazing organ, and it processes light in complex ways before passing on the information in tiny bursts of electricity through the optic nerve to the brain.

To bypass the eye, scientists will have to use technology to process light the same way, and then somehow reinsert the signal into the brain.

“Electrical signals are carried by a million optic nerve fibers,” said Frank Werblin, a neuroscientist at the University of California at Berkeley. “If you could look at the image that is carried by the optic nerve, it is quite different than the image that arrives from the outside world.”

Light that enters your eye gets refracted by the cornea - the surface layer of the eye - and the lens, which is just behind it. An inverted image of whatever you’re looking at falls on your retina, explained Emily Chew, a medical officer at the federal government’s National Eye Institute.

Different layers of the retina then process the image and extract different pieces of information.

Some cells are sensitive to color, others to boundaries of light and darkness. Some cells note movement and the speed at which an image is changing.

“By the time the neural image leaves the retina, there is only information about light changes in space and time,” Werblin said. “The brain reconstructs the image so it looks like a continuous world.”

The truly amazing thing is that this complex symphony of millions of cells happens almost instantaneously. You look up from a book, smile and say, “Hi Mary,” unaware that your eyes and brain have just performed a feat.