Blindness is one of those things that isn’t discussed very much but when it comes to things people fear most, blindness is right there at the top of the list.
Research!America conducted a nationwide poll back in 2016 and found that 88 percent of more than 2,000 respondents considered good vision vital to overall health. And 47 percent said losing their sight would have the most effect on their day-to-day life. Overall, respondents ranked losing vision as equal to or worse than losing hearing, memory, speech or a limb. The top concerns associated with vision loss were quality of life and loss of independence.
having good vision is key to one’s overall sense of well-being,” said Dr. Adrienne Scott. Scott is an assistant professor of ophthalmology at Johns Hopkins University School of Medicine in Baltimore.
When it’s all said and done, we would rather not have to deal with any of these physically disabling conditions, but if you had to choose?
For people dealing with retinal degenerative diseases such as Macular Degeneration or Retinitis Pigmentosa (RP), there is no known cure, no effective treatment capable of restoring one’s lost eyesight. However, research centers from all over the world are taking novel approaches toward developing a treatment for retinal degeneration. Some of these include retina transplants, stem cell therapies, gene therapies, and retinal prostheses.
A Closer Look at the Human Eye
The retina is a thin piece of tissue about the size of a postage stamp at the back of the eye; it’s so delicate that it’s often likened to wet, one-ply toilet paper. Light travels through the eyeball to reach the retina, then passes through several transparent layers of cells to strike the rod- and cone-shaped photoreceptor cells.
The photoreceptors convert light into an electrical signal that travels along a complex network as a pattern of “firing” cells. It goes to a layer of bipolar cells for processing, and they convey the information to a layer of ganglion cells, which do more processing before sending the refined signal up the long sections (axons) of nerve cells that form the optic nerve, which brings the signal to the brain. There, the pattern of electrical pulses resolves into something recognizable—a landscape, printed words, a face. Damage to any of these retinal cells can impair vision, and such damage is a major cause of blindness.
The Argus II – World’s First Commercially Available Bionic Eye
When I first heard about implanting technology to restore eyesight, the first thought that came to mind was the classic TV series, The Six Million Dollar Man. I know I’m dating myself, but my man Steve Austin was implanted with a bionic eye after losing one of his eyes in an accident. The bionic eye provided him with high-resolution eyesight along with some other nifty features such as optical zoom. Well, we’re nowhere near that with our current technology. Still, the technology is very exciting and holds a lot of promise.
One example of a retinal prosthesis is the Argus II, developed by SecondSight. A patient using the Argus II wears sunglasses with a tiny built-in video camera. A small processor that the person carries converts the camera’s stream of video data into simple patterns of light and dark on a grid of 60 pixels. The processor then sends that pattern wirelessly to a chip implanted above the retina, where 60 electrodes stimulate undamaged cells, creating signals that travel up the optic nerve. Two devices being developed by other companies, Retina Implant in Germany and Pixium Vision in France, operate on similar principles.
The Argus II’s 60 electrodes are trying to do the job of the eye’s roughly 125 million photoreceptor cells, so it’s not surprising that they produce extremely crude images.
The Next Generation of Retinal Prosthesis
They say necessity is the father of invention. While the Argus II is certainly revolutionary as a first step in the creation of a sight restoring retinal prosthesis, its limitations are apparent and it’s not quite on the level of the Six Million Dollar Man’s bionic eye. And it is those limitations that has inspired researchers to improve upon devices such as the Argus II. i-VISION is one of a new generation of retinal prostheses. Their goal is to create a device capable of generating high resolution vision for someone who is blind.
The goal of the i-VISION project is to develop a technology capable of providing high-acuity artificial vision to people blinded by outer retina layer diseases, such as retinitis pigmentosa and age-related macular degeneration. In spite of the progressive degeneration of photoreceptor cells caused by these retinal diseases, the neurons responsible for conveying information to the brain remain alive. Retinal prosthesis systems process images of the outside world recorded by a camera and stimulate these neurons by means of electrodes to re-create vision. However, the quality of restored vision in current retinal prostheses is quite limited.
The electrode material interfacing with retinal neurons will be based on graphene, a nanomaterial that will enable the use of more and smaller high-performing electrodes capable of bidirectional (recording and stimulation) communication with the retina. The microelectronics of the prosthesis will implement closed-loop adaptive stimulation strategies and novel wireless technology to power the implant and transmit the electrical stimulus. Advanced in vitro and in vivo imaging and recording techniques will be used to create a personalized map of retina-visual cortex interconnectivity, and thereby optimize the visual acuity restored by the retinal prosthesis.
Biotech Mashup
GenSight’s technology is an entirely different approach from the retinal prostheses discussed so far. Theirs is a hybrid of gene therapy and a wearable device which projects specific wavelengths of light onto a retina containing genetically modified cells.
Like the retinal prostheses, GenSight’s treatment is for people with damaged photoreceptor cells but intact ganglion cells; it inserts the gene into the ganglion cells, whose axons form the basis of the optic nerve.
The treatment makes these ganglion cells act like photoreceptors, responding to patterns of light that pass through the retina and converting them into patterns of electricity that go directly to the brain. Like other forms of gene therapy, the optogenetic method could theoretically restore vision with a one-time treatment.
“We are born with a pool of ganglion cells, and we’re going to die with those same cells,” says Bernard Gilly,
The current optogenetic methods for vision require some hardware. The altered ganglion cells respond to only one wavelength of light, which means that users will need to wear goggles that convert an image of the world into a simple pattern in the correct wavelength.
“It’s not yet clear how well ganglion cells will work as stand-ins for photoreceptors,” says Richard Masland, a senior scientist at Massachusetts Eye and Ear, who developed fundamental optogenetic techniques. “We don’t know how the brain will deal with the abnormal input,” Masland says.
In a healthy eye, the visual signal goes through several stages of processing before it reaches the ganglion cells.
Enter the Bionic Eye
“It’s simplest to use them—and there’s plenty of reason to think that the brain will learn to interpret the information,” Masland says.
Optogenetics researchers, like those taking other approaches to restoring sight, are up against not only the dizzying biological complexity of the eye, but how those inputs get processed by the brain.
Conclusion
As researchers continue to research and develop technologies that are capable of interfacing with the human eye, these highly specialized organs are becoming less and less mysterious. Patients are only beginning to see what’s possible. One thing is clear.; people who are blind are no longer waiting without hope. A treatment is in sight and millions of people from around the world stand to benefit.
Sources
Barcelona Institute of Science and Technology
Proto Magazine
WebMD