Over 25 million people in the world suffer from retinal degenerative diseases. Individuals with these diseases experience loss of vision and eventual blindness, and there is no cure available. However, researchers in the past have developed retinal prosthesis that restores vision to some degree. Unfortunately, the most they are able to see with these devices are edges and spots, so that only the extreme features of any image stand out. Imagine standing outside on a clear fall day, but only feeling the sun and seeing the blurred outlines of trees, rather than being able to enjoy the beautiful foliage surrounding you. While the restoration of any vision is remarkable in itself, visual prostheses still have a long way to go.
Just this past weekend at the annual Society for Neuroscience conference in San Diego, researchers Sheila Nirenberg and Chetan Pandarinath from the Weill Medical College of Cornell University presented a new vein of research that has demonstrated promising results in restoring vision to blind mice. Whereas previous research has focused on trying to increase the power and resolution of the signal from the prosthetic device to the brain, their work focuses on what message is communicated.
In a person with normal vision, photoreceptors (cells in the retina that are sensitive to light) receive the image and convert it into electrochemical signals that get sent to the ganglion cells. These signals are then encoded and sent to the brain, where they are then decoded. Retinal degenerative diseases lead to the death of photoreceptors, the cells responsible for communicating the signals to the ganglion cells and the brain. This means that the visual message stops almost as soon as it reaches the eye, never making it to our minds.
Current retinal prosthesis attempt to recreate this code. However, they simplify the code enormously. Since the signal the brain receives under normal vision is far more complex, Nirenberg and Pandarinath theorized that the problem was not in the power of the signal, but rather in its form. Their retinal prosthetic also recreates the message the brain is supposed to receive, but it is a much better imitation of what our photoreceptors and ganglion cells actually do.
Tests on blind mice were conducted by presenting them with a picture of a baby’s face. Below is a comparison between the true image (left), the image mice see with this new prosthetic device (middle), and the image with the currently used device (right).
The difference between the middle image and the right one demonstrate incredible differences. The eyes and nose are clearly distinguishable, and we can even see some of the baby’s expression. This research thus shows incredible promise in aiding individuals with retinal degenerative diseases, restoring vision to those who otherwise would have been left blind.
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