Millions of people suffer from blindness due to degenerative retinal diseases. The retina is a thin membrane, a few millimeters thick. This tissue is essential for vision, but it can break down in certain diseases, such as retinal degenerative diseases. This can lead to vision problems, including blindness. Researchers at the University of Southern California in the United States are working on a technique to help people suffering from these diseases regain their vision. In BME Frontiers, they explain how a prosthesis allows the retina to function again, using ultrasound.
Retina
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An experiment performed on mice
“This is a step toward a non-invasive retinal prosthesis that works without invasive eye surgery,” explains Dr. Qifa Zhou, lead author of the study. He and his team began by noting that while rods and cones, the light-sensitive cells in the retina, are usually degenerated in this type of pathology, the neural circuits, which are connected to the brain, are often well preserved. Therefore, they hypothesized that directly stimulating the neurons in the retina could restore vision. To test this, the scientists stimulated the eyes of a laboratory mouse with ultrasonic waves, a sound with a much higher frequency than a human can hear. These high-frequency sounds can be directed to a desired area of the eye. In the experiment, this activated small groups of neurons in the blind mouse’s eye, just as light signals would do in the absence of eye disease.
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Future Challenges
The mechanical pressure of sound can activate neurons in the eye and send signals to the brain. “It remains to be understood exactly how the mechanical pressure activated the neurons in the retina,” says Gengxi Lu, co-author of the study. Scientists will also need to adapt the technique to the specific characteristics of humans: they need images that are as sharp as possible. The team’s experiments showed that neurons emit the strongest signal when they are activated about five times per second. But human brains have a much higher computational speed, and at this speed, they will see very jerky images. Film and video game producers know that images can only be displayed smoothly at a speed of 24 frames per second,” said the study authors. When we tested such a high frame rate, the neurons in the mouse’s eyes failed. The researchers hope that ten frames per second will be sufficient. In any case, the retinal prosthesis will be accompanied by a special device. “Special glasses with a camera and an ultrasound transducer, which should give blind and visually impaired people a new view of the world,” explains Dr. Qifa Zhou.
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References
Noninvasive Ultrasound Retinal Stimulation for Vision Restoration at High Spatiotemporal Resolution
