Roughly 40 million people across the world are blind — and, for a long time, most forms of blindness were permanent conditions. The same situation held for degenerative diseases that affect eyesight.
But recently, scientists have made some surprising headway into changing that. New treatments like gene therapy, stem-cell therapy, and even bionic implants are already starting to restore some patients' sight. And these technologies are expected to keep improving in the future.
Here's a look at all the ways scientists have tried — and, increasingly, succeeded — in curing the blind:
1) Gene therapy
Tweaking genes is one promising route to treat blindness.
In 2011, a group led by Jean Bennett of the University of Pennsylvania used gene therapy to treat some patients with a congenital blindness disorder. The patients in question all had a hereditary disease called Leber congenital amaurosis, and they all had mutations in their RPE65 gene. The patients were each given a non-harmful virus that could sneak a healthy copy of the gene into their eye cells. Six out of 12 showed improvement.
Then, in 2014, researchers led by Robert MacLaren, an ophthalmologist at Oxford, presented some promising early results of a very small study of six patients at various stages of a rare, inherited disease called choroideremia. These patients all lacked a protein called REP1, which leads to progressive vision loss. Doctors took the gene for REP1, put it in a non-harmful virus, and injected that virus into the patients' eyes. All reported some improvement in their sight.
"One patient, who before his treatment could not read any lines on an eye chart with his most affected eye, was able to read three lines with that eye following his treatment," wrote Susan Young Rojahn at MIT Technology Review.
Commercial treatments are still a ways off, however. Researchers first have to continue to monitor these patients to see what happens to their vision over the long term (and check for side effects). The FDA currently recommends 15 years of safety monitoring before trying to get a specific gene therapy approved.
2) Stem cells
Rather than fixing up existing cells by adding genes, scientists could also try to replace the defective or dead eye cells altogether. Stem cells can theoretically be coaxed into becoming any bodily cell type, including, say, specialized cells in the retina.
In October of 2014, researchers from the company Advanced Cell Technology (now called Ocata Therapeutics) published a three-year study in the Lancet showing that adding embryo-stem-cell-derived retina cells into the eye had been largely safe for 18 patients and improved vision in 10 of them. (According to
Some researchers are also working on stem cells made from a patient's own cells — called induced-pluripotent stem cells (IPSC). If this technique works, it should have two main benefits: it skirts the ethical issues of embryonic stem cells, and the patient's body won't try to reject the cells. In September of 2014, researchers in Japan reported that they had started the first experiment involving IPSCs in a person. The small pilot study will ultimately involve six patients and track their progress over several years.
3) Bionic vision
Another strategy for treating blindness is to replace human eye parts with electronic ones.
In 2013, the FDA approved the first bionic eye, and it actually does give some sight to the blind. Called the Argus II, it's an eye implant that passes real-time video information into the brain, albeit with very limited resolution and in grayscale.
The Argus II involves a 60-electrode array that gets implanted in the eye to restore some of its function. A camera mounted on a pair of glasses records visual information about the world. This info gets parsed by a small video-processing unit. And then it gets wirelessly transferred to the eye implant, which activates neurons in the back of the eye and sends messages to the brain.
The Argus definitely doesn't bring people anywhere near 20/20 vision. But it provides enough resolution to let people see the outline of a doorway, the movement of a person, or the lines on a crosswalk. Some have even been able to use it to identify letters of the alphabet that are a few centimeters tall. The Argus is currently FDA-approved for people with retinitis pigmentosa, a disease that affects more than two million people around the world.
Other bionic projects are also on the horizon. Some notable ones include research based at the University of Tübingen in Germany that has produced an eye implant that directly senses light. In clinical trials, it has allowed at least one patient to read large letters.
Another project, which is in earlier stages, involves implants for the brain rather than the eye. The idea here is to tap direction into the visual cortex, the brain region that processes sight.
4) Sensory substitution
Sensory substitution is a different technique entirely. The aim isn't to restore vision, per se. It's to use other senses as a substitute.
For example, some blind people are capable of using tongue clicks to "see" their surroundings. They make a sharp sound with their tongue and listen carefully to how the sound reflects off the objects around them. It's basically human sonar. (When animals do this, it's called echolocation.) Daniel Kish, who has been blind since childhood, can echolocate by clicking his tongue. Using this technique, he says that he can see objects fairly far away, as long as they're at least the size of a softball.
In 2011, a study led by David Whitney of the University of California at Berkeley found that six experienced blind echolocators had a spatial precision that was "comparable to that found in the visual periphery of sighted individuals."
And in 2009, a research collaboration including a group at the Polytechnic University of Valencia, Spain, unveiled a helmet that provides a sonar-type experience. It takes real-time images of the world, combines them with depth data from a laser range-finder, and presents that information as audio cues through headphones.
Similar projects have popped up elsewhere, such as the SmartCane, which combines a cane with an ultrasound detection system. And in 2014, Amir Amedi, a neuroscientist at The Hebrew University of Jerusalem, introduced the EyeCane, a small, handheld device that uses two narrow infrared beams to detect nearby obstacles and translate them to either sound or vibration. It was intuitive enough to require almost no training, and people could use it to detect an open door about 15 feet away.
Amedi is also one of several researchers working on projects that translate images into short musical pieces, often referred to as soundscapes. These kinds of software usually scan an image from left to right to create a short sound file. The higher each pixel is in the image, the higher pitch a note is played to represent that pixel.
In 2012 in a paper in PLOS ONE, Amedi and colleagues showed that blind people could use Peter Meijer's soundscape program called The vOICe to read letters and even recognize facial expressions — after only tens of hours of training.
Here's what The vOICe looks like in action: