6.1 Visual prosthetics: retinal and cortical implants
3 min read•july 18, 2024
Visual prosthetics offer hope for those with severe vision loss. stimulate remaining functional cells, while bypass the entire visual pathway. Both use to deliver electrical stimulation based on .
Surgical procedures for retinal implants involve placing electrodes on or under the retina, while cortical implants require brain surgery. Future advancements aim to improve resolution, , and integrate new technologies like and .
Retinal and Cortical Visual Prosthetics
Principles of visual prosthetics
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Top images from around the web for Principles of visual prosthetics
Figures and data in Probing the functional impact of sub-retinal prosthesis | eLife View original
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Improvement in the resolution of Retinal Prostheses - Electronics-Lab.com View original
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Frontiers | Stimulation Strategies for Improving the Resolution of Retinal Prostheses View original
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Figures and data in Probing the functional impact of sub-retinal prosthesis | eLife View original
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- Retinal implants , typically in the inner nuclear layer or ganglion cell layer to bypass damaged photoreceptors (rods and cones) and provide
- Suitable for conditions like retinitis pigmentosa or age-related macular degeneration
- Cortical implants directly stimulate the , bypassing the entire visual pathway making them suitable for conditions causing complete blindness (glaucoma or optic nerve damage)
- Both implants use electrode arrays to deliver electrical stimulation based on captured visual information from external components (camera, image processing unit, and wireless transmitter)
- Implanted components include a , , and electrode array that work together to provide visual perception
Retinal vs cortical implants
- Retinal implants have advantages of utilizing remaining functional retinal circuitry for more natural visual perception and requiring less invasive surgery compared to cortical implants resulting in lower risk of complications
- Limitations include limited applicability as some functional retinal cells are required and limited and field of view due to constraints on electrode array size and placement
- Cortical implants have advantages of being applicable to a wider range of visual impairments, including complete blindness and potential for higher visual acuity and larger field of view due to direct stimulation of the visual cortex
- Limitations include highly invasive surgery with increased risk of complications and less natural visual perception due to bypassing the entire visual pathway requiring more complex image processing and stimulation patterns
Surgical Procedures and Future Advancements
Surgical procedures for prosthetics
- Retinal implant surgery typically involves:
- (removal of vitreous humor)
- Creating a small incision in the sclera
- Placing electrode array either (between photoreceptors and retinal pigment epithelium) or (on the surface of the retina)
- Risks and complications include retinal detachment, inflammation, and device failure
- Cortical implant surgery requires:
- A craniotomy to expose the occipital lobe of the brain
- Placing electrode array on the surface of the visual cortex (subdural) or inserted into the cortex (intracortical)
- Risks and complications include brain injury, seizures, infection, and device failure
Future of visual prosthetics
- Current state shows several retinal implant systems have received regulatory approval (, ) while cortical implants are still in research and development with limited human trials
- Visual acuity and field of view remain limited compared to natural vision
- Future advancements aim to improve electrode array designs for higher resolution and wider field of view, develop more sophisticated image processing algorithms and stimulation patterns, and integrate advanced technologies (optogenetics and stem cell therapy)
- Challenges include developing more biocompatible and long-lasting implant materials, addressing the complexity of the visual system and the brain's plasticity, ensuring safety and efficacy through long-term studies, and improving affordability and of visual prosthetic systems
Key Terms to Review (25)
Access to technology: Access to technology refers to the ability of individuals or groups to obtain and use technological devices and services. In the context of visual prosthetics, it emphasizes the importance of ensuring that those who could benefit from devices like retinal and cortical implants can actually access these solutions, overcoming barriers like cost, availability, and education.
Accessibility: Accessibility refers to the design of products, devices, services, or environments to be usable by individuals with various disabilities. In the context of neuroprosthetics, accessibility encompasses how effectively these technologies can be integrated into daily life for people with disabilities, ensuring they can benefit from advancements in visual prosthetics and other neuroprosthetic applications. It also includes considerations on how societal norms and structures can support or hinder access to these technologies.
Alpha ims: Alpha ims refers to a type of visual prosthetic technology designed to restore vision by directly stimulating the retinal or cortical neurons, allowing for the perception of visual information. This technology is significant because it bridges the gap between lost natural vision and artificial sight, offering hope to individuals with retinal degenerative diseases or cortical visual impairments.
Argus II: The Argus II is a retinal prosthesis designed to restore partial vision to individuals with severe retinal diseases, particularly retinitis pigmentosa. This innovative device converts video images captured by a small camera mounted on glasses into electrical signals that stimulate the remaining retinal cells, allowing users to perceive visual information. The Argus II represents a significant advancement in visual prosthetics and showcases the potential of neuroprosthetic technology.
Biocompatibility: Biocompatibility refers to the ability of a material, such as those used in neuroprosthetics, to perform with an appropriate host response when implanted in the body. This concept is crucial as it determines how well devices interact with biological tissues and influences the functionality and longevity of neural interfaces.
Captured visual information: Captured visual information refers to the data obtained through various imaging techniques, which represent visual stimuli as perceived by the eye or interpreted by the brain. In the context of visual prosthetics, this term connects to how devices, like retinal and cortical implants, are designed to restore vision by processing and transmitting visual signals to the brain in a way that mimics natural vision.
Cortical implants: Cortical implants are devices that interface directly with the brain's cortex to restore or enhance sensory or motor functions. These implants collect electrical signals from neurons, bypassing damaged areas, and can stimulate the cortex to evoke responses, making them crucial in neuroprosthetic applications for those with disabilities or sensory deficits.
D. J. R. Ahuja: D. J. R. Ahuja is a notable figure in the field of neuroprosthetics, particularly recognized for his contributions to the development of visual prosthetics. His work focuses on the advancement of retinal and cortical implants aimed at restoring vision for individuals suffering from various forms of blindness. Ahuja's research integrates neuroscience, engineering, and medical technologies, making significant strides in understanding how artificial devices can interface with the nervous system to replicate visual functions.
Electrode arrays: Electrode arrays are structured groups of electrodes that are used to interface with neural tissue, enabling the recording or stimulation of neural activity. These arrays can be designed to vary in size, shape, and material properties, allowing for targeted interaction with specific brain regions or neural pathways. The versatility and precision of electrode arrays make them essential tools in neuroprosthetics for restoring sensory functions and enhancing cognitive capabilities.
Epiretinally: Epiretinally refers to a specific approach in visual prosthetics where an electronic device is implanted on the surface of the retina to stimulate retinal neurons directly. This technique aims to restore vision by bypassing damaged photoreceptors, allowing visual signals to be transmitted to the brain. The use of epiretinal implants can provide an alternative method for individuals with retinal degenerative diseases, enabling them to perceive light and shapes.
Field of view: Field of view refers to the extent of the observable world that can be seen at any given moment. In the context of visual prosthetics, such as retinal and cortical implants, field of view is crucial as it determines how much visual information a user can perceive at once. A broader field of view allows for more comprehensive visual input, which is essential for activities like navigation and interaction with the environment.
Informed Consent: Informed consent is a legal and ethical process by which individuals are provided with information about a medical procedure or research study, allowing them to make an informed decision about their participation. This process is crucial in ensuring that individuals understand the risks, benefits, and alternatives before consenting to any neuroprosthetic intervention, highlighting its importance across various applications and interdisciplinary research.
Neuroplasticity: Neuroplasticity refers to the brain's ability to reorganize itself by forming new neural connections throughout life, allowing it to adapt to new experiences, learning, and recovery from injury. This flexibility is crucial for the development of neuroprosthetic technologies as it enables the brain to adjust to artificial systems and potentially restore lost functions.
Optogenetics: Optogenetics is a revolutionary technique that uses light to control neurons that have been genetically modified to express light-sensitive ion channels. This method enables researchers to manipulate the activity of specific neurons with precision, offering groundbreaking possibilities in understanding and treating neurological conditions. By integrating optogenetics into neuroprosthetic devices, scientists can develop advanced therapies for restoring lost functions, especially in the context of visual prosthetics and brain-computer interfaces.
Receiver: In the context of visual prosthetics, a receiver is a component that converts signals into a format that can be processed by the brain or a visual prosthesis. This element is crucial in the functionality of both retinal and cortical implants, as it plays a vital role in translating external stimuli into neural signals that can be interpreted by the visual system.
Retinal implants: Retinal implants are medical devices designed to restore vision in individuals with retinal degenerative diseases, such as retinitis pigmentosa or age-related macular degeneration. These devices work by bypassing damaged photoreceptors and stimulating the remaining healthy retinal cells, enabling visual perception. Retinal implants represent a significant advancement in neuroprosthetics, illustrating current applications and the potential for future developments in vision restoration.
Stem cell therapy: Stem cell therapy is a medical treatment that involves the use of stem cells to repair or regenerate damaged tissues and organs. This innovative approach has the potential to restore function in various neurological conditions by promoting healing and regeneration of nerve cells, and it connects deeply with advancements in neuroprosthetics, case studies showcasing successful applications, and regenerative medicine techniques aimed at neural repair.
Stimulate remaining functional retinal cells: Stimulating remaining functional retinal cells refers to the process of activating the surviving neurons in the retina of individuals with vision loss, particularly those affected by conditions like retinitis pigmentosa or age-related macular degeneration. This approach is a crucial component of visual prosthetics, which aim to restore vision by bypassing damaged areas and directly engaging the functional cells that can still respond to light or electrical signals.
Stimulator: A stimulator is a device designed to produce a specific response in biological tissues, often by delivering electrical impulses. In the context of visual prosthetics, stimulators play a crucial role in enabling artificial vision by interacting with neural pathways and mimicking the function of healthy retinal or cortical cells. These devices can restore or enhance vision for individuals suffering from vision loss due to various conditions.
Subretinally: Subretinally refers to the placement or implantation of devices or materials beneath the retina, the light-sensitive tissue at the back of the eye. This approach is significant in visual prosthetics, particularly in retinal implants, as it directly targets the area where visual signals are processed before being transmitted to the brain. By positioning devices subretinally, it aims to restore vision by stimulating retinal cells that may still be functional despite other damage.
University of California, Berkeley: The University of California, Berkeley (UC Berkeley) is a prestigious public research university located in Berkeley, California, known for its significant contributions to various fields including science and engineering. It has played a crucial role in advancing knowledge and innovation, particularly in areas like neuroprosthetics and visual prosthetics through research and development of retinal and cortical implants.
Visual acuity: Visual acuity is the clarity or sharpness of vision, often measured by the ability to discern fine details at a specific distance. It plays a critical role in assessing the effectiveness of visual prosthetics, such as retinal and cortical implants, as these devices aim to restore or enhance this clarity for individuals with visual impairments.
Visual cortex: The visual cortex is the part of the brain responsible for processing visual information. Located in the occipital lobe, it plays a crucial role in interpreting signals received from the eyes and is essential for perception of shapes, colors, and movement. This region is vital in understanding how visual prosthetics work, as both retinal and cortical implants aim to restore vision by bypassing damaged pathways and directly stimulating this area of the brain.
Visual perception: Visual perception is the process by which the brain interprets and organizes visual information from the eyes to create a meaningful representation of the surrounding environment. This involves not just seeing but also understanding and processing the images, colors, shapes, and movements we encounter, allowing individuals to navigate and interact with their surroundings effectively.
Vitrectomy: Vitrectomy is a surgical procedure that involves the removal of the vitreous gel from the eye. This operation is commonly performed to address various retinal issues and can play a critical role in the success of visual prosthetics, especially retinal implants, by clearing the pathway for these devices to interface effectively with the retina.