Summary of Key Points
This article focuses on the technology of visual prostheses that aim to restore vision to the blind, analyzing the principles, advancements, and advantages and disadvantages of the four main types of such prostheses currently in use: retinal surface, subretinal, epiretinal, and cortical. It highlights that subretinal prostheses represent the most promising approach (with systems like PRIMA enabling patients to regain the ability to read). Musk’s claims about a “blindness-reversing” cortical prosthesis have been criticized as exaggerated; such prostheses can at best produce scattered light spots, far from achieving “superhuman vision.” The article also discusses the commercial challenges faced by some of these technologies (for example, the discontinuation of Argus II by Second Sight), emphasizing the need for a balance between therapeutic effectiveness and practical feasibility.
Detailed Analysis
1. Why are visual prostheses needed? – The challenge of neural blindness
Visual problems in healthy individuals (such as cataracts) can be resolved with surgery, but neural blindness (caused by conditions like retinal macular degeneration or complete eye damage) is much more difficult to treat. Gene therapy can only slow the progression of the disease but cannot restore damaged vision. Scientists have turned to brain-computer interfaces to bypass the damaged areas and directly stimulate the nerves, giving rise to visual prostheses.
In simple terms, a visual prosthesis acts as an “artificial eye” that stimulates the nerves (retina or cerebral cortex) to generate visual perception.
2. Retinal surface prostheses: Once the star, now on the decline?
Representative product: Argus II by Second Sight
How it works: A camera on a pair of glasses captures images, which are then converted into electrical signals by a processor. These signals are transmitted to electrodes implanted in the eye to stimulate the ganglion cells in the inner layer of the retina, ultimately reaching the brain.
Problems: The signals received by the retina (which process light and convert it into visual information) are not in a format that the brain can understand directly. Stimulating the retina directly results in “phosphene” effects (scattered light spots), allowing patients to avoid large obstacles but not to see complete images.
Commercial failure: Despite an investment of over $300 million, only 32 million units were sold before the product was discontinued in 2019. The devices required replacement if damaged, and they also posed limitations with MRI scans due to their design.
Conclusion: Retinal surface prostheses have not been successful, leading Second Sight to shift its focus to cortical prostheses.
3. Subretinal prostheses: The current leader in hope for vision restoration
Representative product: PRIMA system (acquired by Hawker’s Science)
How it works: A tiny chip (2mm × 2mm, with 378 pixels) is implanted beneath the retina to replace damaged photoreceptor cells. A camera on glasses captures images, which are converted into infrared light and projected onto the chip. The chip converts this light into electrical signals that stimulate bipolar cells in the middle layer of the retina, allowing the brain to process the visual information.
Advantages: The signals are more naturally decoded by the brain, enabling patients to see coherent shapes rather than just scattered light spots. Clinical trials have shown that 80% of patients could read (two letters at a time), and some were able to perform tasks like playing cards or reading an eye chart.
Limitations: These prostheses are effective only for patients with damaged photoreceptor cells (such as those with macular degeneration) and may not be useful for those with damaged neural pathways, although this group constitutes a significant portion of blindness cases.
Domestic progress: A passive prosthesis developed by researchers at Fudan University does not require external power and can detect infrared light, potentially making it more convenient to use in real-world applications.
4. Cortical prostheses: The reality behind Musk’s “blindness-reversing” claims
Representative products: Orion system and Musk’s “Blindness-Reversing Vision” technology
How it works: Electrodes are directly implanted in the cerebral cortex to stimulate visual perception.
Advances: The Orion system has enabled patients to see light spots and learn to navigate their environment, though the vision is not as clear as that achieved by subretinal prostheses. Musk’s claims of “superhuman multi-spectral vision” (e.g., detecting infrared light) are somewhat misleading, as other prostheses (like PRIMA) can already achieve similar effects.
Limitations: This technology is challenging to develop due to the complexity of the cerebral cortex, and current implementations only produce scattered light spots.
5. The focus of technological competition: Practical solutions over fancy claims
Current visual prostheses are far from providing “superhuman vision.” Patients’ primary need is to regain basic daily functions (such as reading and walking). Subretinal prostheses like PRIMA offer practical benefits, while Musk’s claims about cortical prostheses seem more like sensational marketing rhetoric.
Future directions: Subretinal prostheses need to increase the number of pixels (currently 378 compared to the 150 million in a healthy retina) and add color recognition capabilities. Cortical prostheses must improve signal calibration to convert scattered light spots into clear images.
Conclusion
Visual prostheses are bringing hope to the blind, but subretinal prostheses represent the most feasible solution for now. Musk’s claims about cortical prostheses should be approached with skepticism. Technological progress requires gradual steps: first, enabling patients to see, and then improving the quality of their vision.