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 Table of Contents  
REVIEW ARTICLE
Year : 2021  |  Volume : 59  |  Issue : 1  |  Page : 52-55

Bionic eye: An iconic innovation


1 Rangaraya Medical College, Kakinada, Andhra Pradesh, India
2 Vydehi Institute of Medical Sciences and Research Centre, Bengaluru, Karnataka, India
3 Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India

Date of Submission12-Nov-2020
Date of Decision22-Dec-2020
Date of Acceptance13-Jan-2021
Date of Web Publication27-Mar-2021

Correspondence Address:
Mr. Tarun Kumar Suvvari
Rangaraya Medical College, Kakinada, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_168_20

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  Abstract 


The bionic eye is a visual prosthesis that restores the vision fully or partly in blind people suffering from retinitis pigmentosa and macular degenerations. Many bionic eyes have completed human clinical trials and become functional but still need newer technical approaches to make it available to all people. A bionic eye illuminates the dark world of blind people. To date, many bionic eyes were developed like Argus II Retinal Prosthesis System, Artificial silicon retina and many more, whereas Gennaris Bionic vision System is the recent advanced bionic eye. In our paper, we have covered the basic structure and working of the bionic eye, projects on the bionic eye to date, vision through the bionic eye, implants and restoration of sight, limitations, and the future of the bionic eye.

Keywords: Bionic eye, retina, vision, visual prostheses


How to cite this article:
Suvvari TK, Madhu MT, Nagendra S. Bionic eye: An iconic innovation. TNOA J Ophthalmic Sci Res 2021;59:52-5

How to cite this URL:
Suvvari TK, Madhu MT, Nagendra S. Bionic eye: An iconic innovation. TNOA J Ophthalmic Sci Res [serial online] 2021 [cited 2021 May 6];59:52-5. Available from: https://www.tnoajosr.com/text.asp?2021/59/1/52/312301




  Introduction Top


People having a near or distance vision impairment are estimated to be at least 1 billion globally that could have been prevented or has yet to be addressed. Uncorrected refractive error, cataracts, and diabetic nephropathy are the major causes of vision impairment and blindness. The most common age group suffering from vision impairment and blindness is over 50 years.[1]

The eye receives a light stimulus and transforms into a nerve impulse, which runs along the optic nerve reaching the visual cortex and gives rise to visual sensation. The retina is the innermost membrane of the eye that contains photoreceptors (rods and cones), and the macula (fovea centralis) is the most sensitive spot, and cones are concentrated at that point. The retina transforms light energy into an electrical stimulus and transmits them to the brain through optic nerves to create vision.[2]

A bionic eye is a form of a neural prosthesis intended to restore lost vision or partially amplify existing vision. The bionic eye was developed in view of patients with vision loss due to the degeneration of photoreceptors like retinitis pigmentosa (RP), macular degeneration. Visual prosthetic implants are suitable for patients with defects in light processing functions (damage to the retina, macula, and optic nerve). But for patients who were born blind, it was not convenient to implant a bionic eye them due to not well developed optic nerve.[3]


  Overview of Basic Structure and Working of the Bionic Eye Top


The bionic eye is a visual prosthesis which helps to restore the vision fully or partly. Visual prostheses are implanted based on neuronal electric stimulation at different locations along the visual pathway, i.e., subretinal, epi-retinal, optic nerve, and visual cortex.

The bionic eye consists of image sensors, radio transmitters, microprocessors, receivers, and retinal chips. This electronic system helps blind people to get back good vision. Bionic eyes have a computer chip located at the back eye and linked to a small video camera built into glasses, which they wear. The camera's captured images are focused on the chip, which converts it into an electronic signal and sends it to the brain. Electrodes on the implanted chip cover these signals into electrical impulses to stimulate cells in the retina that connect to the optic nerve. These impulses are then passed down along the optic nerve to the brain's visual cortex, where they are interpreted as an image. The images produced by the bionic eye do not have high clarity, but they are good enough to recognize the things/places.[4],[5]


  Projects Till Date on Bionic Eye Top


Argus II retinal prosthesis

Argus II Retinal Prosthesis System is also called an “artificial retina” or “bionic eye.” It is the epi-renal implant and approved by the US Food and Drug Administration on February 14, 2013. Argus II consists of a mini video camera, the transmitter set up into eyeglasses, a video processing unit (VPU), and implanted retinal prosthesis (array of electrodes).[6] The video camera captures images and transforms it into electronic data with the help of VPU, which sends signals to a wireless receiver (the retinal prosthesis electrodes). The electrodes sent the electronic signals to bypass the damaged retina and transmit directly to the brain's visual cortex and interpreted as visual images. The criteria to get implant Argus II are aged 25 or older, aphakic or pseudophakic, having bare light or no light perception in both eyes, and previous history of good visual acuity.[7]

Artificial silicon retina

Artificial silicon retina (ASR) is a subretinal implant, a silicon microchip of 2 mm diameter that contains approximately 5000 microelectrode-tipped micro photodiodes and is powered by incident light. It is a solid-state biocompatible chip that contains an array of photoreceptors. It is implanted to replace the functionality of defective photoreceptors.[8] The need for external supply was eliminated in the ASR. The ASR was shown excellent vision restoration and did not lead to any side effects like rejection, inflammation, neovascularization…etc.[9]

Harvard/Massachusetts Institute of Technology Retinal Implant

It is an epi-retinal implant where a microelectrode array replaces damaged photoreceptors. The image acquisition was using a charged couple device (CCD) camera. The patient spectacle holds the power source and camera. The subretinal stimulator (array of electrodes) is placed beneath the retina in the subretinal space, which receives image signals from the camera and the stimulator chip, decodes signals, and stimulates retinal ganglion cells. The secondary receiver coil was sutured around the iris.[10],[11]

Multiple units of artificial retinal chipset system

Multiple units of artificial retinal chipset system (MARC) uses a CCD camera input and radio frequency signals to transmit the image into the microchip present in the retina. The image has a resolution of 100 pixels, which is achieved using a 10 × 10 array. It contains a platinum/rubber silicon electrode array placed inside the eye, which stimulates the cells. It also consists have a secondary receiving coil mounted near to the cornea. An external mini low-power CMOS camera was attached to an eyeglass frame. It captures an image and transfers the visual information and power to the intraocular components through radiofrequency waves. The intraocular prosthesis will decode the signals and send electrical stimulus to retinal neurons through the electrodes, which visualize images acquired by the CMOS camera. The MARC system has a compact size of 6 mm × 6 mm, good diagnostic capability, and low stress on the retina.[12]

There are many more similar projects mentioned above like Alpha IMS (subretinal visual implant),[13] holographic technology (based on optogenetics),[14] microsystem-based visual prosthesis, implantable miniature telescope,[15] photovoltaic retinal prosthesis (PRIMA), intracortical visual prosthesis….etc.


  Recent Advances in Bionic Eye Top


Gennaris bionic vision system

Gennaris[16] is a project by the Monash Vision Group (MVG) of Monash University in collaboration with Alfred Health, Grey Innovation, and MiniFAB. It is designed in a way where people with optic nerve damage can also get vision.

Gennaris consists of headgear with a camera, a vision processor unit and software, a wireless transmitter, and a series of 9 mm × 9 mm tiles for implanting into the brain. The video recorded by the camera will be sent to the vision processor, where it will be processed to extract the required information. The data will be transmitted wirelessly to the circuitry within each implanted tile. The data will be converted into electrical pulses, which will stimulate the brain through the microelectrode array. The visual pattern will be created with combinations of up to 473 spots of light (phosphenes), which will provide necessary information for the user regarding indoor and outdoor environments and recognize the presence of people and objects around them. The headgear of gennaris encases MVG's wireless transmission technology, sending data to up to 10 implants where each can stimulate 43 points of the human visual cortex. Because of direct involvement with the cortex, MVG's technology has hopes to assist most people who have total blindness also.[16]

Many projects related to the bionic eye are still under clinical trials. Approximately 1 million electrodes are necessary for natural sight. Developers are currently working on implants with 240 electrodes and peripheral electrodes to improve the size of the person's visual field.


  Vision through the Bionic Eye Top


The bionic eye technology is complex. It depends on the specific eye or prototype, as well as the associated condition. The bionic eye architecture consists of both external and internal components.[17] The external components include glasses with a video micro camera mounted in it and an external connection coil. The Visual Processing Unit (VPU), which is a portable computer customized for the patient., the internal component is the implant, and it consists of the receiver's coil, electronic case, microelectrode array.[17],[18]

When the system is turned on, the micro-camera in the glasses records and transmits the images to the VPU. The image is converted into electrical stimulations and sent to the external transmitter coil. These signals are then transmitted to the receiver coil of the implant. The receiver coil and electronics case are sutured to the sclera of the eye. The received signals are decoded, and stimulation output is generated, sent to the microelectrode array. Microelectrodes deliver stimulation to the retina. The impulses are relayed to the brain through the normal optic nerve tract, generating vision.[18],[19]


  Implants and Restoration of Sight Top


The flickering light is designed to reflect an object's fundamental form in front of the camera, with its approximate height, width, and position. The electrical stimulation of the surviving neurons causes the person to perceive tiny light spots called phosphenes. A phosphene is a phenomenon of experiencing seeing light without light actually entering the eye - like the colours you may see when you close your eyes.[20],[21]

These phosphenes can be used to map out the visual scene in bursts of light in anyone with a bionic eye. The vision provided by a bionic eye, therefore, is not like a natural vision. It is a set of flickering spots and shapes that the individual uses to view the world. The vision created by the system is distinct from the premorbid vision of the patient. To process light patterns, patients must understand its working. To interpret the camera image, recipients need to use these irregular flashes. After postoperative care and years of rehabilitation, several individuals who acquired the implant were able to identify everyday objects, faces of loved ones, even cross streets, and read large-print books without aid.[20],[21]


  Global Marketing on Bionic Eye Top


Bionics (a combination of biology and electronic equipment) is gaining an increase in demand in India. Bionics is still in its developing stages, but many hospitals and medical institutes favor using bionics rather than organ transplants or traditional methods such as a wooden leg/marble/glass eye.

Bionic eye or retinal implant was co-invented by an Indian origin Scientist, Dr. Rajat N Agrawal, an ophthalmologist and retina surgeon, University of Southern California, USA. He is currently working in collaboration with the All India Institute of Medical Sciences, and IITs develop a cheaper native variant of the bionic eye so that people in India can afford it. The natively developed implant is assumed to be Rs 5 lakhs, which is affordable and very less than Rs 45 lakhs' present cost. He was the founder of a nongovernmental group called “Retina India” to research retinal implants.[22]

North America currently dominates the global market; some reasons include a patent for Argus II, higher per capita, and increased awareness. Following North America, Europe and Asia-Pacific are leading. The Asia-Pacific market is filled and is penetrated only to a limited extent. The market has been growing since 2012 and is expected to surge in the upcoming years. Unfortunately, the awareness about the bionic eye is still less than the assumption.[23]

Limitations

The ultimate aim of the invention is to reach maximum people, so it is all about the cost for Bionic eye, which is $30,000 approximately where many people cannot afford it. The cost is the main factor of the bionic eye; hopefully, the cost will decrease, and these will become more common in the medical world in the coming years. The bionic eye is not suitable for all blind people (e.g., glaucoma); it is mainly for people who have retinal damage due to RP …etc. The percentage of restoration of vision is not high enough. Unfortunately, the vision offered by a bionic eye is not clear enough for recipients to rely on to navigate the world since they generate streaky images and are too slow to catch rapid movements. Overall, the vision still falls short of a natural human eye. Researchers hope potential bionic eye implants can generate higher resolution vision, but this has inherent challenges. The Argus system allows recipients to say the difference between forms, motion, and light. However, since only 60 electrodes are part of the system, it does not allow us to see in the same way that healthy eyes operate. In comparison, we will need around a million electrodes to achieve the natural vision. However, the Argus company plans to add more electrodes in future models.

Another factor why the bionic eye cannot replicate human eye vision is due to lack of perception of color as the retina has many types of neurons, but the electrodes are too large to target individual types selectively. This long procedure is surely a very expensive one and may not be covered by medical insurance. Apart from that, recipients must learn the working of the device and the interpretation of flashes. The patient must use head motions to scan the area, which is surely tedious. The long-term stability and long-term impact of the system's electronic components on the retina are still not well established.

The future of bionic eye

Although the vision provided by the bionic eye is far from that of a natural eye, this system has endless opportunities for improvement. Many surgeons are now becoming aware of the benefits of the bionic eye over the traditional glass eye, but choosing these over surgical and medical treatments is still a long way down the road.

The major focus is to increase the number of electrodes in the implants and decrease host immune response, contact blood clotting, and device failures. Future implants may enable people to see in color and they could also be extended to a broader spectrum of diseases causing blindness. We need to increase the number of electrodes that can produce sharp, colorful, and more functional vision. The upcoming generation of Argus II retinal stimulator is under design with 60 controllable electrodes, which can project high beam rays and form high-resolution images. Technology is advancing more and more every day, and with inventions like this, it is quite likely that in the near future, vision loss will be curable, and its permanence will be a thing of the past.


  Conclusion Top


The research and development in bionics are developing day by day. Bringing back vision through a bionic eye will be a boon to blind people in the upcoming days. There is a need to investigate several technical limitations and missing links while developing a bionic eye. On the other hand, integrative courses bridging medical and technical knowledge like biomedical engineering, biotechnology have been greatly underestimated in developing countries, although the scope is rising recently. Let us hope that the future research on the bionic eye will bring out more accurate devices than the current ones.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Introduction
Overview of Basi...
Projects Till Da...
Recent Advances ...
Vision through t...
Implants and Res...
Global Marketing...
Conclusion
References

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