Making Artificial Vision Look More Natural

Bionic vision used to seem like a medical impossibility, but new tests involving electrical stimulation of retinal cells may give the blind hope for more natural vision.

Researchers behind a new study - published in the journal Neuron - used electrical stimulation of retinal cells to produce the same patterns of activity that occur when the retina sees a moving object. This is a step in the right direction to restoring natural, high-fidelity vision to blind people.

In the past few years, the first artificial vision technology has come on the market, allowing people who've been blinded by retinitis pigmentosa to regain some of their sight. A remarkable breakthrough, this technology still has a long way to go, as it only allows patients to do simple tasks like walk through a doorway or read headline-sized letters. One example is the Argus II, approved for treating retinitis pigmentosa in 2013.

"It's very exciting for someone who may not have seen anything for 20-30 years. It's a big deal. On the other hand, it's a long way from natural vision," Dr. Chichilnisky, who was not involved in development of the Argus II, said in a statement.

Researchers from Stanford University in California have built upon such technology by targeting specific cells in the retina - the neural tissue at the back of the eye that converts light into electrical activity.

"We've found that we can reproduce natural patterns of activity in the retina with exquisite precision," said E.J. Chichilnisky, Ph.D., a professor of neurosurgery at Stanford's School of Medicine and Hansen Experimental Physics Laboratory.

The retina contains photoreceptor cells that detect light and convert it into electrical signals - cells that those with retinitis pigmentosa lack. The key to artificial vision is to bypass the need for these photoreceptor cells.

Natural vision - including the ability to see details in shape, color, depth and motion - requires activating the right cells at the right time.

This new study may do just that, by electrically stimulating a type of retinal ganglion cell called parasol cells, known to be important for detecting movement, and its direction and speed. Researchers figured out what pattern and at what speed electrical stimulation was needed to stimulate the parasol cells. Once they did, they were able to reproduce the same waves of parasol cell activity that they observed with a moving image.

"There is a long way to go between these results and making a device that produces meaningful, patterned activity over a large region of the retina in a human patient," Chichilnisky admitted. "But if we can handle the many technical hurdles ahead, we may be able to speak to the nervous system in its own language, and precisely reproduce its normal function."