Two startup companies say they plan to start clinical trials to treat blindness by combining an emerging technology called optogenetics with high-tech goggles that can beam light into the eye.

The companies, GenSight Biologics of Paris and Bionic Sight, a startup out of Weill Cornell Medical College in New York, both say a combination of wearable electronics and gene therapy has a chance to restore vision by re-creating the retina’s ability to sense light.

Both companies are aiming to help patients with a degenerative eye disease called retinitis pigmentosa, which destroys light-sensing cells in the retina. If the approach works, it could in theory be used to treat any type of retinal disease that involves the loss of these cells, called photoreceptors.

Optogenetics, a form of gene therapy, offers an unconventional but potentially powerful way to bypass damaged photoreceptors. Using the technique, scientists add genetic instructions to a different type of retinal cells, ganglions, so that they become light-sensitive instead.

Working with the Institut de la Vision in Paris, GenSight has developed a pair of goggles containing a camera, a microprocessor, and a digital micromirror that will convert images the camera captures into bright pulses of red light in order to stimulate the modified cells.

When tested in blind monkeys and rats, the technology appeared to restore their ability to see, says GenSight CEO Bernard Gilly, but only a test in human volunteers who are able to describe what they perceive after being treated will be definitive. He expects a human study to start this year.

The companies are also closely tracking results from an initial human test of optogenetics carried out last March in Texas. In a trial being led by RetroSense Therapeutics, recently acquired by Allergan, a blind woman became first person to receive an optogenetic treatment to help restore her vision.

That study has so far enrolled four patients, according to David Birch of the Retina Foundation of the Southwest, where the trial is taking place. Each patient gets an injection into the eye of an engineered virus carrying a gene from algae, which instructs cells to make the light-sensitive protein. The team hasn’t yet reported its results, so it’s unknown whether the subjects have gotten any of their vision back.

The RetroSense study relies on natural light to activate the cells. That could limit the treatment’s effectiveness, because the light-sensing proteins only respond to specific wavelengths of light, and low levels of ambient or natural light may not be bright enough to trigger them.

Richard Masland, an ophthalmology professor at Harvard Medical School and a scientific advisor for RetroSense, says that is why companies are looking into goggles or other “light adaptation machinery” as way to beam light of the right wavelengths and intensity into the eye.

Also pursuing a combination of goggles and optogenetics is Bionic Sight, a startup founded by Sheila Nirenberg, a neuroscientist at Weill Cornell Medical College. The company said in January that it would partner with the gene-therapy company Applied Genetic Technologies to begin clinical trials by 2018.

It’s still unclear what sort of vision will result from stimulating the ganglion cells, as these cells normally act to relay nerve impulses and don’t receive light directly. Nirenberg says her goggles will convert light into a “neural code,” or a pattern of pre-processed pulses, which will look to the ganglion cells as if they are coming from other cells in the retina.

Daniel Palanker, an ophthalmology professor and director of the Hansen Experimental Physics Laboratory at Stanford University, is skeptical that Nirenberg’s neural code will help. That’s because there are around 30 types of retinal ganglion cells, some of which respond to light while some respond to motion and some to differences in contrast. No one set of light patterns would be able to communicate with all of them, he says.