Seeing the reality of artificial vision
Initial testing for visual cortical prosthesis yields successful implantation, activation in first subject
Orion I, like Argus II, is also expected to involve a relatively short implantation procedure. The surgery involves making a small opening on the back of the skull over the occipital lobe in order to gain access to the subdural space for placement of the electrode array over the primary visual cortex. Preoperative MRI mapping is performed to guide the implantation.
“Everyone’s brain is different in shape and size, and the electrode array needs to lie directly over the visual cortex on the medial aspect of the brain,” Dr. Pouratian explained.
“Preoperative MRI allows us to identify the best place to enter the skull and ensure that the array is placed on the optimal location over the visual cortex to restore vision,” he added.
The electrode array is tunneled through the subdural space and held in place through apposition of the brain and the falx without needing any accessory for fixation. The surgery also involves implanting the generator into the skull.
“We have adapted existing neurosurgical approaches so that the technique will be within the skillset of most neurosurgeons,” Dr. Pouratian said. “One of the key aspects in developing the Orion I was to develop a device that would be both easily adoptable from a surgical perspective while achieving practical outcomes for patients so that they would gain some useful form of vision.”
As with Argus II, there will be a postoperative fitting step for customizing the exact amount of current on each electrode.
However, because the brain is not as smooth as the retina, an additional mapping step is needed.
“Representation of the visual world on the brain is much more complicated compared to mapping of the retina,” Dr. Pouratian said.
“While the brain mapping presents a significant challenge, Second Sight has been performing studies in preparation for the Orion I clinical trial,” he added. “The company is in a good position to complete the needed psychophysical testing because the Orion I has adequate resolution, sufficient power, and the flexibility to stimulate with complex patterns.”
The surgery to place the off-the-shelf neurostimulator was performed after Second Sight completed its preclinical testing program to establish the safety of implanting and stimulating the Orion I. The company is preparing to submit its IDE application to the FDA in order to gain approval to begin the Orion I clinical trial this year.
“The original plan was to enroll more than one subject into the initial study using the off-the-shelf neurostimulator,” Dr. Pouratian said. “Rather, however, based on the very positive outcomes and what we have learned from this first patient, we feel justified going forward directly with the Orion I feasibility study under FDA supervision.”