Holographic technique could lead to bionic vision

RESEARCHERS are testing the power of holography to artificially stimulate cells in the eye, with hopes of developing a new strategy for bionic vision restoration. Computer-generated holography, they say, could be used in conjunction with a technique called optogenetics, which uses gene therapy to deliver light-sensitive proteins to damaged retinal nerve cells. In conditions such as retinitis pigmentosa (RP) - a condition affecting about one in 4000 people in the United States - these light-sensing cells degenerate and lead to blindness.

“The basic idea of optogenetics is to take a light-sensitive protein from another organism, typically from algae or bacteria, and insert it into a target cell, and that photosensitizes the cell,” explained Shy Shoham, biomedical engineering professor of the Technion-Israel Institute of Technology.

Intense pulses of light can activate nerve cells newly sensitized by this gene therapy approach. But Shoham said researchers around the world are still searching for the best way to deliver the light patterns so that the retina “sees” or responds in a nearly normal way.

The plan is to someday develop a prosthetic headset or eyepiece that a person could wear to translate visual scenes into patterns of light that stimulate the genetically altered cells.

In their paper in the February 26 issue of Nature Communications, the Technion researchers show how light from computer-generated holography could be used to stimulate these repaired cells in mouse retinas. The key, they say, is to use a light stimulus that is intense, precise, and can trigger activity across a variety of cells all at once.

“Holography, what we're using, has the advantage of being relatively precise and intense,” Shoham said. “And you need those two things to see.”

The researchers turned to holography after exploring other options, including laser deflectors and digital displays used in many portable projectors to stimulate these cells. Both methods had their drawbacks, Shoham said.

Digital light displays can stimulate many nerve cells at once, “but they have low light intensity and very low light efficiency,” Shoham said. The genetically repaireAir Max 90 NS GPX