The human eye is an incredibly complex organ, and researchers continue to actively investigate how the eye functions and, in some cases, why it does not. An estimated 36 million people worldwide are blind, and an additional 217 million people have moderate to severe impairment of their vision. How many of these cases are avoidable? How can science help us reverse visual impairment and even blindness?
Reversing Blindness with Gene Editing
The most common genetic condition affecting vision is known as retinitis pigmentosa. Globally, around 1.5 million children are born with retinitis pigmentosa, a condition which causes the cells on the retina to deteriorate over time. This usually starts with a loss of night vision, followed by tunnel vision, and eventually can end in blindness.
Since retinitis pigmentosa is a genetic condition, it is caused by a genetic mutation. If cells from a healthy retina can be inserted into the eye, they could dominate over the cells with the mutation to either slow or stop the retinal degeneration. However, using cells from someone else’s healthy retina runs the risk of the foreign cells not being accepted by the new host body. Fortunately, new approaches to gene editing like the CRISPR/Cas9 enzyme mean that we can snip out unwanted sections of our own genes.
In a recent study published in the journal Nature, researchers took skin cells from patients with retinitis pigmentosa and used a known technique for turning them into multipurpose cells (called pluripotent stem cells). They then removed the mutation through CRISPR gene editing. When they tested the cells 10 days later, the mutation was still gone. The next steps will be to test whether the cells can be put back into the afflicted retina with positive results.
Researchers are also looking at reprogramming the eye’s own cells to address congenital issues like retinitis pigmentosa and other degenerative diseases like age-related macular degeneration. For example, scientists from the National Eye Institute (part of the National Institutes of Health in the U.S.) recently found that Muller glia, cells that act as connective support between neurons in the eye—or, in other words, retinal glue—could be reprogrammed to function as photoreceptors in the eyes of mice that were born blind, specifically the rods that allow us to see in low light.
Reversing Blindness with Bionic Eyes
Another approach to reversing genetic conditions like retinitis pigmentosa is through replacing the entire affected eye. The Bionics Institute of Australia has created a prototype bionic eye and their first eye transplant was performed in 2012. The female patient reported being able to see flashes of light right away, and scientists are working toward shapes.
In 2015, at a hospital in Colorado, doctors created a bionic eye by implanting a microchip into the retina of a retinitis pigmentosa patient. The microchip coordinates with a pair of glasses which wirelessly transmit video to the chip which stimulates her optic nerve to then send that visual information to her brain. She can see outlines and shadows, but her vision is still far from 20/20.
Researchers are also studying whether bionic eyes could be used to address other causes of vision impairment. In 2015, a British patient got a bionic eye implant to reverse the effects of macular degeneration.
Other studies are focused on whether or not 3D printers can get in on the action. Researchers have been able to print “an array of light receptors on a hemispherical surface” which is a first major step toward printing a bionic eye, perhaps making such a device more accessible and more efficient. And, of course, there is an app that allows you to see things as a bionic eye would see them from the National Vision Research Institute.
What Kinds of Blindness Are Avoidable?
Although many of these advances in technology are focused on blindness or eventual blindness that a patient is born with, 80% of all vision impairment cases are considered avoidable according to the World Health Organization. The WHO census finds the main causes of blindness or visual impairment globally to be cataract, glaucoma, age-related macular degeneration, corneal opacities, diabetic retinopathy, childhood blindness, and infectious eye diseases like trachoma or onchocerciasis. Instances of avoidable blindness are most common in south east Asia and the western Pacific, and least common in Europe and the Americas.
The cases are expected to double in the United States by 2050, according to a report from the National Institutes of Health, and also worldwide according to the World Health Organization. But don’t get too worried about your own eyes just yet. This estimated increase is likely due in large part to shifts in population demographics. Population growth in developing nations where visual impairment rates are higher tends to outpace that in developed nations. The fraction of the population over the age of 50 also continues to increase and 80% of people who are either blind or have moderate to severe vision problems are 50 years of age or older.
One very important initiative toward addressing these avoidable types of blindness is the charitable organization Hellen Keller International. HKI works to prevent avoidable blindness and also to improve the lives of the visually impaired through programs established by evidence-based research to combat the “causes and consequences of blindness.” Their research has shown direct links between malnutrition, lack of access to proper healthcare, and gender inequality to increased visual impairment in at-risk populations.
Hellen Keller, who founded Hellen Keller International, was one of the most influential voices of the early 1900s. She famously became both blind and deaf before the age of two due to what is reported as an “acute congestion of the stomach and brain,” although a firm diagnosis has never been made. Her teacher, Anne Sullivan, taught her the concept of language and then how to communicate and eventually read and write. Hellen Keller became the first blind and deaf person to earn a bachelor’s degree and fought for women’s suffrage and labor rights.
The legacy of Hellen Keller lives on in the efforts of Hellen Keller International to serve the most underprivileged communities suffering from visual impairment and through the work of the American Civil Liberties Union, of which she was a founding member.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
