What Are Bionic Eyes for the Blind?

According to the Centers for Disease Control and Prevention (CDC) estimates, vision loss and blindness affect about 7 million Americans.¹ 

Most people use glasses, contact lenses, or even lens implants to help their vision. However, people with severe vision loss or blindness have often benefited less from the available treatment options. 

Fortunately, one technology is changing all that and making vision restoration a reality—bionic eye implants.² 

People with severe vision loss can be fitted with bionic eyes to facilitate the capture and transmission of light stimuli to the brain and help them with their vision. 

What Are Bionic Eyes?

A bionic eye is an electronic eye capable of restoring sight for people with severe damage to the retina. 

The retina is the light-sensitive part at the back of the eye, which contains light-sensitive cells (rods and cons). 

These photoreceptors receive visual stimuli and transmit them to the brain through the optic nerve bundle. Damage to the retina cells affects this process, causing vision impairment.

Bionic eyes do not restore normal vision. They also cannot discern color, although researchers are working to incorporate this capability in newer versions.

These special devices aid blind people in navigating the world around them more independently by producing a series of flashing spots and shapes that help:³ 

• Perceive light
• Identify shapes
• Detect motion
• Read large print 

Through bionic eyes, vision function improves gradually with training, thus improving quality of life.

How Do Bionic Eyes Work?

All types of bionic eye systems consist of implants and external components that work together to produce some level of visual perception. 

The implant consists of the following parts:

• Microelectrode array. Receives electrical signals that stimulate retinal cells to transmit information to the brain
• Receiver. Sends electrical signals through the cable to the microelectrode array at the retina
• Electronics case. Houses the coil and acts as a wireless receiver for electrical signals
• Cable. Relays signals from the receiver to the electrode array at the retina

The external components include the following:

• Mounted camera. Mimics the natural eye by capturing the visual scenes at eye level and transmitting video images to the processing unit
• Video processing unit (VPU). Converts the video images into electrical signals and sends them to the electrode array, which delivers them to the brain; also involved in contrast enhancement and edge detection⁴ 

Working Mechanism

Below is a step-by-step explanation of how the retinal prosthesis system works to enable sight:

1. The processing unit receives the video images captured by the camera. Here, they’re transformed into electrical stimulation commands. 
2. These electrical commands are sent to the retinal implant and transmitted to the electrode array via the cable. 
3. The electrode array then emits small pulses that activate the surviving retinal cells, enabling them to deliver visual signals via the optic nerve to the brain. 
4. The brain’s visual cortex then interprets the signals, enabling the person to perceive different elements of their environment (light, shapes, edges, and motion). 

The Science Behind Bionic Eyes

Bionic eyes leverage the remaining retinal cells to transmit visual signals to the brain.

This technology incorporates special glasses, digital data, and electrical impulses to convey visual signals to the visual cortex and offer partial eyesight to people with poor to no vision.

The Argus II Retinal Prosthesis System is the world’s first bionic eye, enabling hundreds of users worldwide to perceive light, movement, and shapes. 

The technology is actively under improvement, with developers hoping to create a device that can mimic the complex functions of the human retina. 

How Do Retinal Prostheses Restore Sight?

Retinal prostheses won’t restore your natural eyesight. The vision restored is black-and-white with no fine details; therefore, it differs from normal vision. Retinal prostheses can help you identify some elements of sight, such as light and shapes.

With training, someone fitted with a retinal prosthesis like Argus II can learn to interpret visual signals in their surroundings or even read large print text.

Who Can Benefit from Bionic Eyes?

A screening session will help your doctor determine whether bionic eyes will work for you. Those most likely to benefit from bionic eyes are middle-aged or elderly individuals with very poor vision due to conditions such as:

• Age-related macular degeneration (AMD). Causes degeneration of the macula, the part responsible for central vision
• Retinitis pigmentosa (RP).⁵ A group of genetic diseases that destroys photoreceptors (rods and cones)
• Choroideremia. A genetic condition that causes progressive degeneration of retinal cell layers like the choroid, retinal pigment epithelium or RPE, and the photoreceptors

Criteria for Candidates

According to the FDA, the ideal candidate for retinal implants must meet the following criteria:

• Be an adult aged 25 and older
• Have low or no light perception in both eyes
• Have a previous history of functional vision
• Be Aphakic (lacking natural eye lens)
• Be Pseudophakic (using lens implants)
• Is willing to undergo post-clinical follow-ups and other recommended procedures

The site and extent of damage will determine the viability of bionic eyes. For example, extensive damage to the optic nerve, visual cortex, or human retina (no viable photoreceptor cells) renders the bionic eyes useless.

Patients must be carefully screened to rule out any issues that can affect the effectiveness of the bionic eye implant.

Bionic Eye Devices and Their Capabilities

The following artificial eyes are approved for vision restoration:

The Argus® II Retinal Prosthesis System

The Argus® II Retinal Prosthesis System by Sight Medical Products Inc. in California is the USA’s only FDA-approved bionic eye design.⁶ It also received the CE mark in Europe in 2011. The CE mark proves that the device has been assessed and meets the safety, health, and environmental protection requirements of the European Union (EU).

The retinal implant helps people who have lost vision due to degenerative eye diseases such as 

• Retinitis pigmentosa (RP)
• Choroideremia
• Age-related macular degenera­tion (AMD)

The Argus II implant has a 60-microelectrode array placed on the retinal surface (epiretinal). The electrode array enables vision by electrically stimulating the few surviving retinal ganglion cells (RGCs) to transmit visual input to the brain for processing. The mounted camera and video processing unit (VPU) provide the visual input. 

According to the American Academy of Ophthalmology (AAO), the longest clinical study of the efficacy of the Argus II system indicated a 90% success rate.⁷

Alpha-AMS Retinal Prosthesis System

The Alpha-AMS system by Retina Implant AG in Reutlingen, Germany, has been CE-certified and commercially available in Europe since 2016.⁸ It’s an improvement of its previous version, the Alpha-IMS (approved in 2013 and later discontinued). 

The Alpha-AMS retinal system has a 1600-microelectrode array placed beneath the degenerated retina (subretinal prosthesis). This makes the surgical process more challenging and prolonged than in Argus II.

Unlike Argus II, which has an external camera, the Alpha-IMS implant can detect light and transfer electronic signals to the microelectrode array. The microelectrodes stimulate the bipolar cell layer inside the retina to transmit visual input to the brain for interpretation. 

IRIS®II Bionic Vision System

The IRIS®II bionic vision system by Pixium Vision was the third bionic eye to be CE-certified in Europe after Alpha IMS and Alpha AMS. The microchip array is placed on the retina’s surface (epiretinal), just like in Argus II.

It differs from the Argus II in several ways:

1. The Iris II System has a 150-microelectrode array.
2. It has a ‘neuromorphic image sensor’ that captures the coordinates and intensities of changing pixels. This process enables the eye to focus on the most important elements of the visual scene.
3. It has a learning retinal encoder, allowing individualized calibration that mimics the retinal ON/OFF pathways.⁹

Although the IRIS II system is still CE-approved, it has not been commercially available since 2018.

The Future of Vision Restoration

The current versions of visual prostheses have shown great potential in future vision restoration. However, more engineering work is needed to make these retinal prosthetics safer and more viable regardless of the cause of vision loss. 

One primary goal among researchers is to increase the number of microelectrodes, which can improve vision clarity.

Ongoing Research and Potential Breakthroughs

As scientists continue to explore the full potential of bionic eyes, future implants may be able to restore vision regardless of cause. 

Other components, such as the camera function, can also be improved to provide users with the best resolution. 

For example, incorporating the zoom function, thermal sensitivity, and other intelligent functions already in use in other areas can improve how bionic eyes work in the future.

Scientists are also exploring alternatives to bionic eyes, such as cortical devices and biological therapies, which may compete with bionic eyes regarding safety and effectiveness.

Currently, the Orion™ cortical prosthesis by Second Sight Medical Products Inc. is in clinical trials.¹⁰ The implant will bypass the retina and directly introduce visual stimuli to the visual cortex for interpretation. Initial findings revealed that participants were able to see phosphenes (seeing stars).

Challenges and Limitations of Bionic Eyes

Despite the main benefit of bionic eyes—enabling users to discern light, shapes, and motion—there are still several challenges, limitations, and risks associated with these devices:

• Bionic eyes do not restore vision to normal due to the limitation in microelectrode density.
• They cannot restore vision for people with completely degenerated retinal cell layers. 
• Bionic eyes cannot perceive color. Users can only see images in black and white.
• The surgery is quite expensive. For example, the Argus II system may cost around $115,000 to 150,000.¹¹
• A non-functioning bionic system can cause medical complications or interfere with procedures such as MRI scans.
• There is always a risk of infection due to surgery.
• The removal procedure can be painful and expensive.

Knowing what’s in the market today and potential enhancements will give you a clearer picture of how bionic eye technology may improve people’s quality of life.

Summary 

• A bionic eye is an electronic eye capable of restoring sight for people with severe damage to the retina. 
• People with severe vision loss can be fitted with bionic eyes to facilitate the capture and transmission of light stimuli to the brain for interpretation.   
• Middle-aged or elderly individuals with very poor vision due to conditions such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are most likely to benefit from bionic eyes.
• The three main types of bionic eyes approved in the USA and Europe are the Argus II, the Alpha-AMS, and the Iris II retinal systems.
• More research is underway to improve the extent of bionic vision correction with the aim of improving the quality of life for people with vision loss.