- Flickr/Grégoire Lannoy
What exactly do you see when you’re blind?
It varies – vision loss manifests in many different ways – but the variety of colors, the sharpness of shapes, and the details that most of us take for granted are usually out of reach.
“The central vision is sort of a blurred mish mosh of colors that is indistinguishable,” Marc Muszynski, a 29-year-old whose vision is slowly fading away, told BuzzFeed. “Around that, the rest of it is pretty bad, too.”
Muszynski’s experience, or something like it, is one shared by many: Vision loss is one of the 10 most common disabilities US adults face. It affects more than 3.4 million Americans over age 40.
Historically, there has been little we can do for someone going blind. Slowly but surely, that’s starting to change.
An ‘audacious goal’
In many cases, diseases that cause blindness damage the retina at the back of the eye, which contains the specialized nerve cells that make vision possible. Since the body only has limited means to repair nerve cells and can’t replace dead ones, this damage is pretty much permanent – at least for now.
The National Eye Institute has launched the Audacious Goals Initiative, the “audacious goal” being finding a way to regenerate those lost nerve cells and restore vision to millions.
Michael Steinmetz, director of extramural research for the National Eye Institute, said he doesn’t think reaching this goal in the next 15 years “is so far from reality.”
As Raymond Iezzi, an eye surgeon and vision scientist at the Mayo Clinic, told Tech Insider: “In the relatively near future we will have the ability to surgically or medically restore sight to the vast majority of patients who have lost their vision.”
If the National Eye Institute and other efforts succeed, blindness could go from a common disability in the US to a rare ailment. Millions of people who lost their vision would be able to see again. We may fall short of these ambitious goals, but research is moving fast.
The ‘bionic eye’
Already, some people who had lost virtually all of their sight due to a rare, incurable genetic disease called retinitis pigmentosa have been able to see again for the first time in years with the Argus II “bionic eye.”
Their restored vision isn’t much like what we’d consider normal, but they can see edges and outlines of figures they couldn’t before, which significantly improves their quality of life, Iezzi told Tech Insider.
Retinitis pigmentosa kills photoreceptors, nerve cells in the retina that convert light into an electrical signal the brain can interpret as vision. Without working photoreceptors, people with retinitis pigmentosa can’t see.
The Argus II is a rough replacement for lost photoreceptors. It translates video images from a camera into electrical signals, which it then feeds to 60 electrodes on a chip that has been surgically implanted on a patient’s retina. That chip stimulates nerve cells that connect to the part of the brain that interprets visual information, just as healthy photoreceptors would.
- University of Michigan/courtesy of Second Sight Medical Products
Scientists at the Manchester Royal Eye Hospital in the United Kingdom are testing the Argus II in patients with a form of age-related macular degeneration, a more common cause of vision loss that also damages photoreceptors.
But Iezzi says the high-resolution vision most people with AMD lose is different than the basic sight the Argus II gives people with retinitis pigmentosa. We’ll have to wait and see whether the device is actually helpful for patients whose vision loss is less severe.
Fortunately, scientists are pursuing other possible treatments at the same time.
For his part, Iezzi is in the initial stages of developing a surgical procedure he thinks could help people with advanced macular degeneration. The disease damages photoreceptors only in the center of the retina – patients still have millions of healthy photoreceptors left in the rest of the eye.
Relocating some of their remaining photoreceptors to the center of the retina could possibly restore the vision they’ve lost without using an implant. If the procedure proves effective after tests in animals, Iezzi thinks it’s possible people might be able to try it in roughly five years.
Scientists are also beginning to test whether various kinds of stem cells could preserve and even help restore vision in some cases of blindness.
AMD, for example, damages photoreceptors because it first kills the cells that take care of them. Researchers are now trying to grow those caretaker cells, called retinal pigment epithelium cells, from stem cells. After growing enough of these cells, a surgeon would implant them into a patient’s eye. The idea is that replacing the missing caretaker cells may preserve a patient’s remaining photoreceptors.
A clinical trial at the University of California-Los Angeles tested retinal pigment epithelium cells made from embryonic stem cells. This type of stem cell is derived from human embryos and can become any kind of cell in the body.
After about two years of follow up, the procedure hadn’t caused serious issues in the 18 patients in the trial, and it seemed the transplanted cells survived, the researchers reported in The Lancet. Putting stem cell products into humans is still so new that the scientists were mainly concerned about safety, but some patients’ vision did improve.
Another clinical trial of a stem-cell treatment, this time for retinitis pigmentosa, is just beginning at the University of California-Irvine.
The stem cells in this trial are called retinal-progenitor cells, which are made from fetal tissue. These cells can become several different types of specialized nerve cells found in the retina. The scientists hope the transplanted retinal progenitor cells will prevent photoreceptors from dying and even produce new photoreceptors, stopping patients with retinitis pigmentosa from losing their vision.
Someday, blind people might be able to get actual replacement photoreceptors from stem cells, rather than support cells. Scientists are already actively testing that approach in mice with some success. That research is still in the earliest stages.
Other approaches to replacing photoreceptors, instead of regenerating them, involve modifying cells patients still have and harnessing them to fill in for lost photoreceptors.
Though retinitis pigmentosa and AMD damage photoreceptors, they leave the rest of the visual system intact. In particular, the cells that transmit information about light from working photoreceptors to the brain are still functional. Those are called retinal ganglion cells.
But without photoreceptors, these ganglion cells are “all dressed up with no place to go,” Rich Kramer, a biologist at the University of California, Berkeley told Tech Insider.
Imagine that photoreceptors act like a magic mirror, translating images from the world into information that can be processed by retinal ganglion cells and eventually the rest of the brain.
When that mirror shatters or goes dark, the retinal ganglion cells are awaiting information that never comes. The photoreceptors can’t let the light in, so your brain never sees it – even though it’s perfectly capable of vision.
Kramer and his colleagues work on one way to leverage these still functional retinal ganglion cells to restore vision: by making them sensitive to light so they can replace dead photoreceptors and do double duty.
To do this, they’ve developed a molecule called a photoswitch that changes shape in response to light. When the molecule gets into retinal ganglion cells, it makes them able to sense light and pass on what they sense to the brain.
After an injection of the photoswitch molecule, previously blind mice behave as if they can see light, Kramer said.
Promising treatments that work in mice often never work in humans. But if this research makes it through animal trials and is successfully tested in humans, it could eventually yield a drug treatment for some causes of blindness. Patients would get periodic injections of the molecule to restore their vision.
There’s at least one other way scientists have tried to leverage those functional retinal ganglion cells. Researchers insert an extra gene into the cells so they make a protein that responds to light. This approach is called optogenetics, and works in a similar way to gene therapy.
But because the gene added is not normally part of the human genome – it’s from a type of algae – scientists will have to be particularly careful in vetting the approach before trying it in humans. For now, it’s used mainly as a research tool to “see” activity in the brains of rodents. Any possible clinical applications are a long way off.
An optogenetic or photoswitch treatment for blindness could eventually make retinal implants obsolete, Iezzi said. Such a treatment could provide more than a million replacement photoreceptors, rather than the 60 electrodes the Argus II provides today. That would mean the brain would get more information about light than is currently possible, and restored vision could one day be much sharper.
An ounce of prevention
Scientists are trying to restore vision in a number of exciting ways, but preventing people from losing good vision in the first place would be even better.
“Protecting a patient’s sight would ultimately have a better impact in terms of their quality of vision than restoring it after it’s been lost,” Iezzi said.
Michael Fautsch, who heads ophthalmology research at the Mayo Clinic, is one of many scientists working on ways to treat diseases that cause blindness and stop the damage before eyesight gets too bad.
He and his team are developing a new drug for glaucoma, a group of diseases that sometimes cause fluid to build up in the eye, putting pressure on the optic nerve and damaging it. What they’re working on would act on the main pathway through which fluid normally leaves the eye to relieve the damaging pressure, he told Tech Insider. Currently, glaucoma drugs target a minor fluid drainage pathway.
Vision research in general is in an exciting place, Fautsch said. Years of research into how different diseases damage the eye and cause vision loss are today helping scientists develop novel strategies for treatment.
“Technology is moving so fast, our understanding is moving so fast, that I think the future holds great promise,” he said.
The promise of the future is that someday, no type of vision loss will be untreatable. Science has a ways to go, but one day it may be inconceivable that so many people ever became permanently blind.