Visionaries For Vision Joaquin Sabherwal

Joaquin Sabherwal (Year 6, Shackleton)

INTRODUCTION

We would all like to be young and healthy forever. However, as people inevitably age, their hair will begin to decolour, their joints will become stiffer, and their skin will begin to wrinkle. The wear and tear of our bodies is unavoidable as we get older, but perhaps one of the worst aspects of the ageing process is the possibility of losing one’s sight.

HOW DOES THE EYE WORK?

Light reflects off objects and into our eyes. These rays of light enter the eye via the cornea, the pupil and the lens, and then focus on the retina. The retina is a light-sensitive tissue at the back of the eye, which sends signals through the optic nerve to the brain. It is these signals that become the images that we see [1].

Figure 1: Light reflects off objects and into our eyes [1][2]

The macula is the area of the retina that gives us our central vision, and the peripheral retina surrounds the macula and gives us our side vision. On the retina, there are about 130 million tiny cells called photoreceptors [2]. These rod- and cone-shaped cells are input cells; they turn light into electrical currents that travel from the output cells, through the optic nerve and to the brain. When light enters the eye, it strikes these cells, which triggers a chemical reaction that sends signals to the brain [3].

Figure 2: The Retina and Photoreceptors [3]

An overwhelming number of people in the world have a wide range of conditions that make them visually impaired, but the main cause of age-related vision loss is macular degeneration. It is a disease that gradually deteriorates the central vision (macula), leaving a blur or a black hole in the focal point of your view.

Retinitis pigmentosa is another common disease that damages the photoreceptors. This disease isn’t restricted to the elderly, as it is genetically inherited and affects 1 in 4,000 people in the USA, regardless of age.

Both macular degeneration and retinitis pigmentosa attack the photoreceptors and in the most advanced forms of these diseases, everyday ordinary tasks (like reading, driving, writing, or even just walking around safely) would be almost impossible without assistance.

Although the damage to the photoreceptors caused by these diseases is serious, the remainder of the retina’s neurons and cells that transfer electrical signals are usually still intact, which means there is hope to cure vision impairment. If scientists are able to find a way to invent something that can imitate the function of photoreceptors, then the signals would be able to be transmitted to the brain in the way that they’re supposed to. Thankfully, that is happening as technology is advancing.

THE INNOVATIONS SO FAR

Researchers have been attempting to invent prosthetic devices that can mimic and fulfil the purpose of the rod- and cone-shaped cells so that blind people might get their vision back. By implanting a tiny device that interacts with the tissue that makes up the retina, scientists have found a way to take the information captured by a camera lens embedded in a pair of glasses that the patient wears, and convert it into electrical signals that get transferred to the brain via the optic nerve. However, most prosthetic devices only provide limited vision, such as bright lights and high-contrast edges.

Argus II, which is a device created by a company called Second Sight, helps patients distinguish patterns of light and identify outlines of basic shapes and movement, therefore helping them to navigate the world more independently. Once the Argus II is implanted at the back of the eye by an experienced retinal surgeon, it is accompanied by external glasses with a built-in camera and a small portable pocket computer, which is a vision processing unit (VPU). The VPU processes what the camera is seeing into instructions that then get sent to the glasses, and the antenna transmits the information wirelessly to the implant in the eye. The implant consists of another antenna (which receives the information) and an array of electrodes. When the information is received, the electrode array fires small pulses of electricity which are sent along the optic nerve to the brain, and the patient learns to interpret patterns of light. Argus II has already been commercialised and is available for patients [4][5].

Figure 3: Argus II [5]

One of the lead scientists working on restoring sight to the visually impaired is an American neuroscientist called Sheila Nirenberg. A neuroscientist is someone who studies the nervous system, including the brain, the spinal cord and nerve cells throughout the body. Her main focus is to decipher and learn the language that the brain understands. To understand the importance of this language, it is essential to examine how the information is actually processed when the brain receives an image.

Figure 4: Healthy Retina [6]

Figure 4, from left to right: when an image enters the eye, it lands on the front-end cells of the retina, the photoreceptors, then it is processed through the retinal circuitry, which extracts information. That information is next converted into code in the form of electrical pulses then travels to the brain. Figure 5 demonstrates how the electrical pulses are sent in a specific pattern that tell the brain what the image is.

Figure 5: Healthy retina sending electrical pulse codes [6]

It’s a very complicated process, as every millisecond, these patterns of pulses are constantly changing, along with the world around you. When the front-cells of the retina shut down due to a degenerative disease like macular degeneration, the retinal circuitry is next to shut down, and although the output cells are left intact, they are no longer transmitting any code.

Prosthetic devices, or bionic eyes, such as Argus II, are most certainly innovative, however they are limited to seeing images that are simple. The device allows the patient to see spots of light and basic shapes, but they are far from providing patients with normal representations of faces, buildings, landscapes, etc. The issue lies in the way that the stimulators are producing code. Sheila Nirenberg suggests that to make the image clearer, there is a need to drive the stimulators to produce normal retinal output. She says, “having the code is only half the story. The other part is having some way to communicate that code into the cells so that they can send it to the brain.”

Nirenberg is currently working on a unique prosthetic system that is made up of an encoder and a transducer. Like the Argus II, Nirenberg’s device also relies on a camera that is embedded in a pair of glasses and the information captured by the camera is sent to the device wirelessly. However, this system does not send electrical pulses directly along the optic nerve. Instead the encoder converts the information into a code that closely matches the code that a healthy retina uses to communicate with the brain and a transducer drives the output cells in the eye (ganglion cells) to fire electrical signals as the code specifies. Essentially, the image goes through a set of equations which mimics the retinal circuitry, and then it comes out as electrical pulses which then travel along the optic nerve.

Figure 6: A damaged retina, with device replacing the photoreceptors [6]

What also makes this different is the pattern of the electrical signals that are fired out. In order to develop this prosthetic system, Nirenberg and her team have had to delve into neuroscience to study what this ‘code’ (pattern of electrical signals) looks like. Trying to understand this code is like learning a new language. The more that they are able to learn how the brain understands this language, the more they are able to mimic the language and therefore communicate with the brain as a normal retina would. This way, they are literally “cracking the code” and finding ways to get the firing patterns to match the activity of normal retinal output, and thus are getting closer to giving the patient an accurate representation of the image in front of them [6][7][8].

CONCLUSION

There is hope for visually impaired people in the future! As technology advances, the understanding of how the body works is deepening, and we will soon be able to create bionic versions of our body parts. Sheila Nirenberg suggests that with her device, there is a potential to enhance it using ultraviolet or infrared light so it could even make blind people have better sight than regular people. This means that not only would people have their sight restored, they would have even better eyesight as their bionic eye would have abilities that a natural eye wouldn’t.

This innovation might even further our understanding of the way that the brain relates to our body parts, and there may be ways to use the same principles discovered here to cure people with other problems. The potential power of being able to communicate with the brain means that the same strategy could be used for the auditory system and the motor system to help people who have auditory issues or motor disorders. By jumping over damaged circuitry in the same way as they have done with the retinal circuitry, scientists could cure numerous other physical impairments - these visionaries for vision could potentially change the lives of more than just the visually impaired! [6]

BIBLIOGRAPHY

[1] EyeSmart — American Academy of Ophthalmology, “How the Eye Works” https://www.youtube. com/watch?v=8e_8eIzOFug – 18/03/2018

[2] EyeSmart — American Academy of Ophthalmology, “How the Eye Works and the Retina” https:// www.youtube.com/watch?v=Sqr6LKIR2b8 – 30/11/2010

[3] Science Art, “How Retina Works Animation-Physiology of the Eye Videos” https://www.youtube.com/watch?v=GkJrQmVRkYM -24/01/2019

[4] Wei-Haas, M., (2017, Oct 19) “Could This Bionic Vision System Help Restore Sight?” https://www. smithsonianmag.com/innovation/could-bionic-vision-system-help-restore-sight-180965305/

[5] SecondSight, “Discover Argus II” https://www.secondsight.com/discover-argus/ - 2019

[6] Nirenberg, S., (2013 Jun 26) “TED-Ed - A prosthetic eye to treat blindness - Sheila Nirenberg” https://www.youtube.com/watch?v=RR08NcoBlms

[7] Nirenberg, S., (2018, Nov 30) “Cracking The Code To Treat Blindness | Mach | NBC News” https:// www.youtube.com/watch?v=76cWyxzX7ds

[8] Nirenberg, S., & Pandarinath, C., (2012, May 7) “Retinal prosthetic strategy with the capacity to restore normal vision” https://physiology.med.cornell.edu/faculty/nirenberg/lab/papers/PNAS-2012- Nirenberg-1207035109.pdf

Azvolinsky, A., (2018, Apr 10) “Vision Restored: The Latest Technologies to Improve Sight”, https:// www.the-scientist.com/news-opinion/vision-restored-the-latest-technologies-to-improve-sight-30104

Barker, P., (2018, Oct 1) “5 inventions bringing sight to the visually impaired” https://www.redbull.com/ int-en/inventions-to-help-visually-impaired-people

Boseley, S., ( 2018, Mar 19) “Doctors hope for blindness cure after restoring patients’ sight” https:// www.theguardian.com/society/2018/mar/19/doctors-hope-for-blindness-cure-after-restoring-patientssight

Gallagher, J., (2012, May 14) “Light-powered bionic eye invented to help restore sight” https://www. bbc.com/news/health-18061174

Jeffries, A (2016, Apr 5) “The Technology That Could Make Blind People See Again” https://youtu.be/ SJUWPD62MTI

Loeffler, J., (2018, Dec 28) “5 Medical Innovations That May Help Cure Blindness:https:// interestingengineering.com/5-medical-innovations-that-may-help-cure-blindness

McDougall, B., (2018, Jun 8) “Australian world-first bionic eye invention ready for sight” https://www. kidsnews.com.au/technology/australian-worldfirst-bionic-eye-invention-ready-for-sight/news-story/93 146b354bdb2b25331664e7300f53c2