Optic nerve stimulation to offer visual aid to blind: study

Scientists are developing a technology that would circumvent the eyeball in order to deliver the message directly to the brain in case of visually impaired people.

Researchers from EPFL in Switzerland and Scuola Superiore Sant'Anna in Italy will be doing this by stimulating the optic nerve with intraneural electrode known as OpticSELINE.

The study was published in the journal 'Nature Biomedical Engineering'.

"We believe that intraneural stimulation can be a valuable solution for several neuroprosthetic devices for sensory and motor function restoration. The translational potentials of this approach are indeed extremely promising," explains Silvestro Micera, a professor of Bioelectronics at Scuola Superiore Sant'Anna.

Blindness affects an estimated 39 million people in the world. Many factors can induce blindness, like genetics, retinal detachment, trauma, stroke in the visual cortex, glaucoma, cataract, inflammation or infection. Some blindness is temporary and can be treated medically. But how do you help someone who is permanently blind?

The idea is to produce phosphenes, the sensation of seeing light in the form of white patterns, without seeing light directly. Retinal implants, a prosthetic device for helping the blind, suffer from exclusion criteria. For example, half a million people worldwide are blind due to Retinitis pigmentosa, a genetic disorder, but only a few hundred patients qualify for retinal implants for clinical reasons.

A brain implant that stimulates the visual cortex directly is another strategy even though risky. The new intraneural solution minimizes exclusion criteria since the optic nerve and the pathway to the brain are often intact.

The teams engineered the OpticSELINE, an electrode array of 12 electrodes. In order to understand how effective these electrodes are at stimulating the various nerve fibres within the optic nerve, the scientists delivered electric current to the optic nerve via OpticSELINE and measured the brain's activity in the visual cortex. They showed that each stimulating electrode induces a specific and unique pattern of cortical activation, suggesting that intraneural stimulation of the optic nerve is selective and informative.

With current electrode technology, a human OpticSELINE could consist of up to 48-60 electrodes. This limited number of electrodes is not sufficient to restore sight entirely. But these limited visual signals could be engineered to provide a visual aid for daily living.