In 2020, it was estimated that 49.1 million individuals from the global population were blind.1 Bionic eye implants are electronic devices with the aim of restoring vision for people with blindness and low vision.
Eye implants generally comprise a pair of eyeglasses, a camera, a data processor unit, and numerous tiny electrodes. The camera is mounted onto a pair of eyeglasses; the electrodes are surgically implanted into or near the retina, ultimately replacing the role of the photoreceptors in the retina.2
Ocular bionic implant basics
A bionic implant is an artificial computerized mechanical body inserted into humans to replace or enhance a natural biological function that has become dysfunctional. Bionic implants can restore numerous lost natural biological functions such as the movement of limbs, hearing, and most importantly vision.2
When the camera for an ocular bionic implant “sees” an object, visual information is transmitted by wire from the camera to the data processing unit, which simplifies and translates the image into an electrical signal.
These electrical signals can then travel via a wire connected to a secondary stimulator implant in the skull and travel to the retinal implant. Or they can travel wirelessly to the retinal implant via infrared light pulses. Once the retinal implant receives the signal it begins stimulating the bipolar cells of the inner retina, permitting artificial vision via the visual pathway.
The electrical stimulation of the retina was initially studied in the operating room where electrical stimulation of the retinal surface via small probes elicited light perception, called phosphenes, in blind patients who were under local anesthesia. Thus suggesting successful elucidation of the visual pathway via electrical stimulation of the retina. As a result, micro-electrode array technology was developed and tested in laboratories to be used as retinal implants.
These implants once developed were surgically implanted in blind participants of phase one clinical trials. Post-implantation laboratory vision testing revealed to investigators the success of using retinal implants as a means to elucidate the visual pathway and create artificial vision in blind patients.3
Cortical brain implants as an alternative to retinal implants
More advanced cortical brain implant technology also exists that accomplishes the same task as the eye implant, but instead of stimulating the retina for artificial vision, it directly stimulates the visual cortex of the brain.3,4
This bypasses a majority of the visual system in attempts to restore vision in a majority of blind individuals. It potentially allows for vision restoration for a wider variety of conditions causing blindness that a retinal implant can’t, such as optic neuropathy.
Bionic implants can be used to return aspects of vision, such as the detection of shapes, edges, and movement via the presentation of flashing light precepts from stimulation of the patient’s nervous tissue. With these bionic implants, irreversible causes of blindness from severe eye trauma, retinal diseases or damage, and optic nerve disease may now be “reversible” to a degree. Such revolutionizing technology is now giving hope for a sense of independence in the lives of blind patients.3
Bionic eye systems to watch
The Bionic Eye System by Bionic Vision Technologies
In 2012, Bionic Vision Technologies began developing the Bionic Eye System designed to improve the vision of patients with end-stage retinitis pigmentosa. The proof of concept trial was first conducted from 2012 to 2014 for the Bionic Eye System.
The success of the trial and the developments in technology at the time led the company to conduct a follow-up clinical trial from 2018 to 2021 for a second-generation retinal implant used in four participants. The findings from this follow-up trial were published in May 2024.5,6
How does the Bionic Eye System work?
Figure 1: Courtesy of Kenan Azizi.
The second-generation implant is a 44-electrode array implanted into the suprachoroidal space behind the retina, thus avoiding any obstruction to the remaining vision of the patient. The location of the implant also permits a patient to receive gene, stem cell, or other future therapies targeting the retina. A camera mounted on a pair of glasses captures live visual information.
The visual scene is sent to a data processing unit via wire, which translates the live visual information into electrical signals. These encoded signals get transmitted via a second wire to a stimulator pack, magnetically connected to an implanted receiver under the scalp, which wirelessly transmits the electrical signals to the retinal implant.
The electrode array then electrically stimulates the residual cells of the retina to allow for the transmission of visual information to the vision-processing centers of the brain via the optic nerve.5,6
Trial success of the Bionic Eye System
The trial found that all four participants did not have serious adverse effects following surgical implantation of the device and use for over 2.5 years.7,8 Although a mild post-operative subretinal hemorrhage was observed in two patients, this resolved on their own after 2 weeks.
Functionality tests showed that 97% of the electrodes remained functional with no complications. Optical coherence tomography (OCT) scans performed throughout the study confirmed the stable positioning of the retinal implants. This information demonstrates the long-term viability of the second-generation bionic eye system.7,8
All four patients demonstrated improvements in localization ability on tabletops and screens, while also improving in mobility and orientation tasks with device use. Additionally, three of the four participants presented advancements in motion discrimination, and two of the four participants substantially improved in tabletop object identification and spatial discrimination.7,8
Even when participants were using the device unsupervised in their own homes they reported being able to safely traverse obstacles, better detect nearby individuals, and explore unfamiliar environments. Therefore, the quality of life of the participants was enhanced with the use of the device.7,8
The PRIMA Vision System by Science Corporation
The Photovoltaic Retinal Implant (PRIMA) bionic vision system was developed by Pixium Vision, who began a clinical trial for device feasibility in five participants in 2017 in Paris, France. The goal of the study was to test the efficacy and safety of the PRIMA Vision System for improving visual acuity in patients with atrophic dry age-related macular degeneration (AMD) at 4 years post-implantation.
The study has since been completed and results were published in the Ophthalmology Science Journal in March of 2024.9,10,11,12 One year after beginning their first study in France, Pixium Vision began a second trial in the United States in 2018 in five more patients for a 3-year post-implantation review. The second trial is anticipated to be completed by December 2025.13
Currently, Pixium Vision’s Assets are owned by Science Corporation, who acquired them in April of 2024, 1 month after the publication of PRIMA’s 4-year post-implantation study. Science Corporation has plans to develop a next-generation PRIMA Vision System with a wide angle camera and more up-to-date electronic hardware.9,14
How does the PRIMA Vision System work?
Figure 2: Courtesy of Kenan Azizi.
PRIMA is a 378-pixel wireless subretinal photovoltaic implant. The PRIMA Vision System is composed of a camera mounted on transparent augmented reality (AR) glasses, a pocket data processor unit, a mini-projector module also mounted on the AR glasses, and the subretinal photovoltaic implant.
The implant had no total obstructive effect on the natural vision of the participants, thus allowing a combination of remaining natural central vision, natural peripheral vision, and photovoltaic-stimulated central vision to be used by the participants.9,10,11,12
The camera mounted on the AR glasses captures live visual information. The live recording is analyzed, processed, and simplified by the pocket data processor unit connected to the glasses via wire. The simplified images are then sent back to the glasses where the mini-projector emits images wirelessly via near-infrared pulses of light onto the PRIMA implant under the retina. To induce visual perception, optical information is converted into electrical stimulation by the photovoltaic cells.9,10,11,12
Trial successful results with PRIMA Vision
The clinical trial revealed initial success with all five participants having light perception restored in blindspots post-implantation. Although initially starting with five participants, two patients had to be excluded from the study in the long term. One participant died from cancer 18 months post-implantation, unrelated to device implantation, and another participant mistakenly received an intrachoroidal implantation.10,11
At 48 months post-implantation the remaining participants all had no decline in natural visual acuity in the implant eye, and all had an insignificant decline in natural visual acuity in the non-treated eye, most likely due to their dry AMD.
ETDRS visual acuity data was also collected at this time, revealing mean EDTRS letter counts of 11.7 letters at initial baseline, 18.2 letters at 48 months without use of PRIMA glasses, and 43.3 letters at 48 months with use of PRIMA glasses with preferred magnification.
This illustrates that all participants experienced significant improvements in ETDRS visual acuity while using the PRIMA Vision System with their individually preferred magnification compared to when they are not. The mean improvement in visual acuity between having the vision system on versus off at 48 months post-implantation was 25.1 ETDRS letters.10,11
In terms of successful functionality, the remaining participants were all able to successfully read food labels, panels, signs, and train timetables using the PRIMA Vision System; thus illustrating the feasibility, relative long-term viability, and positive impact of the device in patients with dry AMD.10,11
Safety findings with the PRIMA Vision System
Safety findings from the study revealed that although a total of four serious adverse events (SAEs) were reported among the initial five participants, they were all deemed unrelated to the implanted device. However, all SAEs have implications for procedure-related causes. The implants were also reported to remain stable without causing any obvious structural changes in the retina in all three participants over 3 years.10,11
Many non-serious adverse events were reported, with a majority reported within 6 months post-implantation, though none raised any long-term safety concerns. Macular microcysts were the most commonly reported non-serious adverse event, seen in three participants, though they all resolved without sequelae. These results suggest that device safety is not a major concern, yet implantation procedures still need refining.10,11
Cortical implants currently in use
Orion Visual Cortical Prosthesis System by Cortigent
Second Sight Medical Products (now Vivani), first founded in 1998, was the medical product company that developed the infamous Argus II, an epiretinal implant and visual prosthesis device, on which the Orion Visual Cortical Prosthesis System was based.
In March 2011, Argus II was approved for commercial use in the European Union, and in February 2013, the US Food & Drug Administration (FDA) approved Argus II under a Humanitarian Device Exemption to restore visual perception in patients with severe blindness due to retinitis pigmentosa (RP).
After years of research and successfully improving the lives of many blind patients with RP, the Argus II was discontinued in 2019 due to financial difficulties. Vivani thus shifted their focus onto their brain implant clinical trial, Orion, which began with six participants in 2017 via the subsidiary company, Cortigent.15,16
How does the Orion Visual Cortical Prosthesis System work?
Figure 3: Courtesy of Kenan Azizi.
The main component of the Orion Visual Cortical Prosthesis System by Cortigent is a subdural electrode array implant with the purpose of restoring vision in bilaterally blind patients from non-cortical causes.16
The Orion System consists of a 60-electrode array implanted on the medial subdural surface of the occipital lobe through cranial neurosurgery, a pair of glasses with a centrally mounted camera, a body-worn video data processor unit, and a sealed electronics package with a wireless receiving antenna implanted on the skull.16,17
The camera on the glasses captures the live visual scene sending it to the processor unit via wire, where it processes and translates the video into electrical pulse patterns which are then emitted wirelessly to the implant.
Electrode activation stimulates the visual cortex in blind patients, bypassing any diseased or injured visual pathway and provides the perception of light patterns to the blind patient. In order to interpret the light patterns, training and visual rehabilitation is necessary for these patients to perform functional vision tasks.17,18
Prospective success with the Orion Visual Cortical Prosthesis System
The Orion early feasibility study began in 2017 with six participants at the University of California, Los Angeles (UCLA) and Baylor College of Medicine. The ongoing clinical trial reached its 5-year post-implantation milestone in July of 2023 and Vivani released an update announcement regarding the results thus far. The study is anticipated to be completed in December of 2024, when more detailed information will be published.18
Currently, three of the original six participants are still participating in the study as the other three participants had their devices removed for reasons deemed unrelated to device safety or reliability. The remaining participants reported no device malfunctions at 5 years post-implantation with continuous daily use.
A seizure was reported in one of the six participants within the first 3 months post-implantation; however, it was quickly resolved with no permanent harm caused. No SAEs have been reported since then. Orion’s Progress from October 2019 described the occurrence of only five non-serious adverse events post-implantation between two of the six participants, but these adverse effects weren’t explicitly named.17,19
Efficacy of the Orion System
Five of the original six subjects at 3 years post-implantation were evaluated on the effectiveness of the device. All five participants performed significantly better with the Orion System turned on than turned off for tasks involving localizing and pointing to a lit-up square on a computer screen and identifying which direction a line is moving on a computer screen. Two of the five subjects achieved measurable Grating Visual Acuity.19
Four of the original six participants participated in an assessment at 3 years post-implantation where an independent specialist would visit the homes of the participants and observe them while they performed various activities of daily living, such as navigating a sidewalk or sorting laundry while using the Orion System.
All four subjects had positive to mildly positive results with the Orion turned on versus when turned off for these activities. This illustrates Orion’s positive impact on the lives of these participants, suggesting that more promising results are anticipated when the trial is completed.19
The Intracortical Visual Prosthesis by the Illinois Institute of Technology
The Intracortical Visual Prosthesis (ICVP) was developed by a multi-institutional team at the Illinois Institute of Technology (IIT). The team began a phase one clinical trial in five participants in 2020.
The goal of the study is to test the feasibility and safety of eliciting visual precepts via the ICVP and its wireless floating microelectrode array (WFMA) technology in patients who were blind due to ocular injury, optic nerve diseases, and photoreceptor degeneration.20
The study is still ongoing, and the team at IIT has published an article about reaching the 2-year post-implantation milestone in one of their participants with the first successful surgical implantation of the ICVP.21
How does the ICVP work?
Figure 4: Courtesy of Kenan Azizi.
The ICVP contains 25 implanted microchip stimulator modules, each consisting of 16 microelectrodes. This means 400 microelectrodes are implanted on one side of the brain’s visual cortex via neurosurgery.20,21,22
Similar to the Orion System, the ICVP System uses a pair of glasses with a mounted camera capturing the live visual scene and uses a processor to wirelessly translate and transmit the visual scene into commands for stimulation by the stimulator modules.20,21,22
However, unlike the Orion System, additional electrical packages and antennas are not necessary, as the stimulators directly receive the commands. These commands allow for excitation of the visual cortex producing light precepts in what are like dots of light.20,21
Current success of the intracortical visual prosthesis
The latest publication from the team at IIT reveals they found the prosthesis provides participants with an improved ability to perceive people/objects, navigate, and perform basic, visually guided tasks.23 These accomplishments indicate the possible benefits ICVP will have for current and future participants, especially as more data is collected.23
The team is aiming to study each participant for 1 to 3 years post-implantation, and their goal is to recruit more participants for more ongoing studies to ensure safety and efficacy of the ICVP.21
Other bionic implants in development
“Blindsight” by Neuralink
Neuralink, a neurotechnology company founded by Elon Musk in 2016, is a hot topic in the world of bionic implants. The company’s groundbreaking success after their first human surgical brain implant has drawn attention worldwide, as it has allowed for a 30-year-old quadriplegic man to wirelessly control a computer with his mind.24
Elon Musk wants to use this same technology to restore vision in blind patients through a second project titled Blindsight, announced on March 20th, 2024. On September 17, 2024, Neuralink received Breakthrough Device designation from the FDA for Blindsight.25
What is the N1 brain-computer interface chip?
Neuralink uses what they call the N1 brain-computer interface (BCI) chip, which contains 1024 electrodes distributed across 64 threads, but Neuralink has plans to develop next-generation chips with 16,000 electrodes.
With how small the implants are, it is possible to implant multiple chips and multiply the number of electrodes across both sides of the visual cortex, thus theoretically enhancing the brain stimulation and therefore the visual perception in the patient.24
How does the N1 chip compare to other cortical implants?
Figure 5: Courtesy of Kenan Azizi.
The N1 chip would work similarly to the cortical brain implants previously discussed. However, what makes the N1 BCI implant so unique is its use of thin flexible threadlike microelectrodes, completely wireless interface, and robotic surgical implantation.24
The use of these threadlike electrodes allows for more precision and less damage during implantation, in contrast to the standard rigid electrode arrays used in current implants. Through robotic surgery, those threadlike electrodes can be implanted precisely in the visual cortex while adjusting for brain movements, and avoiding cerebral vasculature.
Unlike the previously discussed cortical brain implants, Blindsight will be completely wireless. Through the use of glasses with mounted cameras, a smartphone, and the N1 BCI chip, the whole system would be invisible to the outside world.24,26
What’s in the pipeline for the future of visual bionic implants?
The future of visual bionic implants is bright! With the immense success of the numerous technologies currently in development and under study, there is tremendous potential in helping millions of people worldwide.
Although the generation of helpful rudimentary vision was a success in all of these implants, there is still room for improvement with increasing the number and size of the electrodes.22 This becomes especially important when considering the limited anatomical real estate in the retina. Science Corporation and Bionic Vision Technologies recognize this and are currently working on their electrodes.7,9
More large-scale clinical trials are required before commercializing these devices to the public. Cortigent has a road map that indicates that after the early feasibility study, they will be working on the conversion of the prototype model into a commercial model for another pivotal clinical trial.16
Neuralink is currently trying to develop new ways to implant their BCIs to make upgradeability easier. The current method of craniectomy and subdural implantation creates significant scar tissue and makes explanation difficult.
However, Neuralink has discovered that implantation through the dura bypasses this issue, but not without increasing difficulties with visibility and penetrance through the thick dura. These issues are being addressed with the concurrent use of imaging modalities to view brain vasculature during surgery and new surgical techniques being developed by Neuralink.26
In closing
Bionic implants have great potential to restore vision in blind patients. In addition, many of these implantation procedures are reported to be safe and effective, even after long-term usage of the implanted device.
Currently, there are several visual bionic implants in development for restoring lost vision due to a variety of diseases. All of the implants under study have reported initial success in enhancing the visual acuity and quality of life of the once-blind clinical trial participants.
As the technology continues to advance, and more clinical trials are conducted, bionic eye implants will likely become high in demand.
