By Alexandra Demetriou
Mark Humayun, MD, PhD and Amir Kashani, MD, PhD were featured on Voice of America’s “VOA/TEK,” a news program dedicated to highlighting the most cutting-edge technologies and medical breakthroughs around the world. The episode details the strides Humayun and his team have made in their mission to restore sight, the lasting impact of their innovations on patients’ lives and the research that continues to evolve at the Dr. Allen and Charlotte Ginsburg Institute for Biomedical Therapeutics.
The episode opened with a feature on Anna Kuehl, a patient who regained her eyesight after receiving a stem cell-based retinal implant as part of a study at the USC Roski Eye Institute. Kuehl had suffered from progressive vision loss due to age-related macular degeneration (AMD), a disease that affects approximately 11 million Americans. She was diagnosed with the dry form of AMD, which causes a layer of cells called the retinal pigment epithelium (RPE) to die off. RPE cells are responsible for nurturing photoreceptor cells in the eye that enable proper eyesight. The loss of functional RPE and photoreceptor cells gradually blinds patients like Kuehl and, historically, there was little doctors could do to help.
Kuehl was one of a handful of people who participated in a clinical trial led by Kashani at the USC Roski Eye Institute, which used stem cells to grow new RPE cells for dry AMD patients. Kashani and Humayun implanted the brand-new cells, grown in a single layer on a biocompatible membrane, to replace the dying RPE cells in Kuehl’s retina.
“When they’re just-formed RPE cells, they’re as young and vibrant as they can get,” Humayun explains in the episode. “They’re incredibly resistant to stressors in the environment, which otherwise would kill older RPE cells. These vibrant, tough cells that we put in Anna’s eye were put in a very destructive environment –– of course, because that environment had killed her cells –– so the question was, would these cells survive?”
The cells did better than survive. They restored Kuehl’s eyesight to the point that she could clearly see the faces of her loved ones once again. During her interview with “VOA/TEK,” Kuehl recalls the moment she first realized she was able see whole faces after the surgery, while she was watching TV: “I jumped back! I was so excited,” she recounts with a laugh.
Kuehl is one of hundreds of patients who have benefitted from the innovations Humayun and his colleagues continue to develop at the USC Ginsburg Institute. Another such patient is Terry Byland, the only person in the world to have two “bionic eyes.”
Byland has a genetic form of blindness called retinitis pigmentosa (RP), which initially causes tunnel vision and eventually leads to complete vision loss. The disease left him in total darkness for 26 years until he received an Argus I and later an Argus II implant, which feed visual information from a camera to the optic nerve to restore some eyesight. The tiny implants are placed inside the eye along the retina and allow patients like Byland to perceive some light and basic motions. The implants offer Byland practical benefits, such as noticing a car in front of him, as well as invaluable gifts, such as the opportunity to see the outline of his now 30-year-old son –– a sight Byland had last witnessed when the boy was only five.
There’s no doubt these implants have brought immeasurable benefits to patients’ lives, but they didn’t arrive at the clinic without challenges. Humayun describes creating the implant as “skiing uphill” because of the immense difficulty of the entire process, from determining what kind of electrical stimulation would produce vision to figuring out how to mount an implant in the tiny, delicate retina. It took an impressive feat of ingenuity and perseverance to develop the implants in the first place, and Humayun is determined to keep making progress. Recently, Argus patients in Korea have begun reporting that they can see the top letter on an eye chart –– a development Humayun finds promising and exciting.
In addition to enhancing the previously described implants, a brain implant based on the Argus platform is also in the works. This device, called Orion, sits directly on the surface of the brain to stimulate a region called the visual cortex. It is intended for patients who have damage to the nerve connecting the eye to the rest of the brain. A patient wears glasses with a tiny camera mounted on the bridge, similar to the glasses and camera used with the Argus retinal implant. As the wearer turns his or her head to take in the surroundings, the camera, instead of transmitting visual information to the implant on the retina, now directly transfers it to the brain implant.
Currently, the implants only sit on one of the brain’s hemispheres and transmit signals through 60 electrodes –– a small quantity compared to the number of signals the estimated 140 million neurons in one’s visual cortex can carry. Second Sight, the company that manufactured the Argus and Orion implants, hopes to eventually increase the number of electrodes, implant devices in both hemispheres and add features like heat vision to help patients identify their family, friends and pets. Six patients have received the Orion implants so far, and they are working with researchers and doctors to retrain their brains to adapt to this new modality of visual information.
“It’s been exciting because every time I come here, I get to see something,” says Benjamin Spencer, one of the Orion implant recipients, during one of his post-implantation testing visits. “It may not be full vision yet, but it’s something, and for someone who hasn’t seen anything in 25 ½ years, that is a huge accomplishment.”
To watch the full “VOA/TEK” episode, click here.
Mark Humayun, MD, PhD, is a co-inventor of the Argus implant series. He is a minority equity owner in Second Sight Medical Products, Inc. and receives royalty payment.
The technology to produce the stem cell–based retinal implant is exclusively licensed to Regenerative Patch Technologies LLC from the University of Southern California, the California Institute of Technology and the University of California, Santa Barbara. Humayun has an equity interest in and is a consultant for Regenerative Patch Technologies LLC.