For people with the incurable genetic eye disorder retinitis pigmentosa, the world can be a dark place.
Genetic mutations cause their photoreceptors, the cells in the retina at the back of the eye that convert light into an electrical signal the brain can interpret, to stop working and die. Without functioning photoreceptors, people with retinitis pigmentosa go blind.
But with the help of a retinal implant, or “bionic eye” called Argus II, some patients with the rare disorder are regaining their sight.
A clinical trial of the device has been ongoing in 10 vision centres across the United States and in Europe. Researchers from those centres published results from the first three years of the trial in Opthamology, the journal of the American Academy of Opthamology.
Before using the Argus II, at best patients could detect only bright light. With the device implanted and turned on, some patients did significantly better on vision tests, like touching a white square on a black monitor and finding a door in real life.
Beyond lab tests, visual rehabilitation experts evaluated the effects of the Argus II in the daily lives of patients. For 65% of the study participants, the device positively impacted their lives, improving their quality of life and their ability to perform basic tasks.
How it works
The Argus II system has two separate components: a camera and visual processing unit a patient wears (both shown below), and the surgically implanted receiving antenna and electrodes.
The camera and visual processing unit do what the photoreceptors in people with retinitis pigmentosa no longer can: convert visual information from light into electrical signals the brain can understand.
An antenna on the glasses transmits the data from the camera and visual processing unit to a receiving antenna implanted into the patient (shown below).
The data received goes to an array of 60 electrodes implanted over the macula, the part of the retina that is normally the most sensitive.
The electrodes produce small pulses of electricity that stimulate the nerve cells still left in the retina, which then carry information about the stimulation to the part of the brain that interprets this into vision.
What it can do
It takes therapy and practice for patients who have been blind for decades to “relearn how to see” from the implanted electrode’s stimulation, Dr. Mark Humayun, one of the scientists behind the Argus II, told the Retina Times, a publication of the American Society of Retina Specialists.
Besides needing a refresher on how to interpret visual information at all, patients have to adapt to the new kind of information the Argus II electrode provides.
Allen Zderad, a retinitis pigmentosa patient who got the retinal implant through the Mayo Clinic, described what he saw when his implant was turned on like this: “It’s a pulsing light, it’s not like regular vision where it’s, like, constant, it’s the flash, and I’ve got to be able to interpret the changes in that shape.”
“It’s crude, but it’s significant,” Zderad went on to say in a video from the Mayo Clinic.
Zderad’s doctor, Raymond Iezzi, says his patient reconstructs a scene and objects in front of him with the information from the electrodes, plus his visual memory and cognitive skills.
The Argus II isn’t able to restore completely normal, sharp vision, but the functionality it does give back to people who previously could only perceive bright light is not negligible.
In the clinical trial, 89% of patients performed significantly better on a test that required touching a white square on a black screen using the retinal implant system, compared to when they tried the test with the implant turned off.
Patients were also better at an important practical task with their implants turned on, successfully identifying a door 54% of the time on average, compared to only 19% of the time without implants on.
Humayun says the Argus II can improve patients’ ability to identify doorways and curbs, sort laundry into light or dark loads, see where people are, and perceive obstacles in front of them when walking.
The clinical trial only included 30 patients, which is a small number that makes it difficult to draw definitive conclusions, the researchers wrote.
But earlier data from the study about the device’s safety and benefits was enough for the FDA to approve the Argus II for people with severe vision damage from retinitis pigmentosa.
In September 2014, Second Sight Medical Products, the company that makes the Argus II system, announced that researchers at the University of Manchester in the UK would try the device out for patients with age-related macular degeneration, a common cause of blindness.
If the retinal implant system can be proven to help patients with other diseases that left them blind, it could make the world brighter for many.