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Low vision specialist critical to success of retinal implant
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Patients with light perception or no light perception due to retinitis pigmentosa may experience improved mobility with the implantation of a retinal prosthesis, but targeted postoperative training by a low vision specialist is crucial to patient outcomes, according to one surgeon.
“My hope is that soon there will be a segment of optometrists who would dedicate themselves to training with this device on orientation and mobility,” Mark S. Humayun, MD, PhD, told Primary Care Optometry News.
Humayun, co-inventor of the Argus II Retinal Prosthesis System (Second Sight), explained how the system works.
A camera in the patient’s glasses captures information and sends it to a video processor and battery worn on a belt or strap. The information is encoded and powered, and the data and power are sent wirelessly to the device implanted in the macula, “which stimulates the remaining nerve cells and sends the information from the optic nerve to the brain and allows the otherwise blind person to see again,” Humayun said.
FDA approval
The FDA approved the Argus II in 2013 for patients with retinitis pigmentosa and light perception or no light perception in both eyes under a Humanitarian Use Device exemption.
“The FDA realized the number of patients with end-stage retinitis pigmentosa is very small,” Humayun explained, “so this is the equivalent of an orphan drug. They permitted 30 patients to be in the study, but, because it’s a small number we had to follow them for at least 3 years. That becomes 90 cumulative years. Since then there have been reports of 5-year data.”
Humayun said the device is primarily intended to improve a patient’s orientation and mobility.
“If you have light perception or no light perception, this allows you to see a doorway or a tree branch,” he said. “Your cane used as it is by most blind/visually impaired individuals doesn’t give you information on objects above the waist. It gives you added information to use with cane travel about objects to orient you to the door or tell you where the windows are. It tells you where the crosswalk hash lines are so you can follow them. It allows you to look at the head of a person talking to you so you can be more engaged. If someone sticks out a hand to shake yours, you can see that. You can tell where the plate, cup and utensils are located on a table.
“The patient can avoid object collision and recognize objects,” he continued. “It allows more social interaction and even fun activities, such as bowling and basketball.”
Humayun said one patient said he was excited to see fireworks and the solar eclipse that just occurred. He said a grandmother was able to see her grandson playing soccer by seeing to which side of the field the groups of bodies would move.
He noted that the device’s resolution does not allow for reading sentences or watching TV. For outside situations where the light may be too bright, “it has an inversion mode, which makes everything darker and only makes the car that’s sitting there or the mailbox bright,” he added.
A study showed that two-thirds of wearers found the Argus prosthesis useful in unfamiliar environments, Humayun said.
“If they’ve been blind for a long time, they know what’s in their living room or kitchen,” Humayun continued, “but it helps them when they get into unfamiliar environments.”
Postoperative training
The Argus is activated about 2 weeks postoperatively, Humayun said, to allow the soft tissue swelling to go down.
He stressed the importance of training after the initial implantation.
“These training sessions can take 2, 3 or 4 hours,” Humayun said. “Second Sight Medical is trying hard to get a code for an optometrist to get reimbursed for working with the Argus. We definitely need that.”
He noted that Second Sight’s website provides information on where optometrists can refer patients who may be eligible for the procedure.
Humayun discussed the Argus in his keynote address at the Envision Conference. – by Nancy Hemphill, ELS, FAAO
- References:
- Da Cruz L, et al. Ophthalmology. 2016;123(10):
- 2248-2254;doi:10.1016/j.ophtha.2016.06.049.
- Ho AC, et al. Ophthalmology. 2015;doi:org/10.1016/j.ophtha.2015.04.032.
- Humayun MS. Opening plenary session.Presented at Envision Conference 2017; July 27-29,2017;Phoenix.
- For more information:
- Mark S. Humayun, MD, PhD, is the Cornelius J. Pings Chair in Biomedical Sciences; a professor of ophthalmology, biomedical engineering, and cell and neurobiology, and director of the Institute for Biomedical Therapeutics and Sensory Sciences Institute; and co-director of the University of Southern California Roski Eye Institute, Los Angeles. He can be reached at humayun@med.usc.edu.
Disclosure: Humayun is co-inventor of the Argus II Retinal Prosthesis and holds patents on the Argus technology and stock in Second Sight Medical Products.