“One thing I do know. I was blind but now I see!” – The Bible passage of the man born blind healed by Jesus is surely best known to everybody who has had Religious Education. In the tale Jesus uses mud, which he puts on the man’s eyes and after washing it off in a river, the man can see for the first time in his life. It seems like Rapunzel’s blinded prince did a little better – he regained his ability to see through Rapunzel’s tears which dropped on his eyes.
Being topic of many tales and therefore equations, losing sight seems like losing the most important sense. But it’s widely spread – one third has impaired sight due to aging or illness or is entirely blind. One is blind if he’s completely sightless or is having less than ¹/₁₀ of normal vision in the more efficient eye when refractive defects are fully corrected by lenses. In 75% of the cases the reason for vision loss is a disease of the eyes. The most common ones are retinitis pigmentosa, macular degeneration, glaucoma and optic neuritis as well as a trauma, for example after an explosion.
And like the Pharisees couldn’t believe the story of this man coming along and healing blindness, restoring sight to the blind has always been the preserve of miracles – until today.
Today we replace the word “miracle” with “technology” – we replace cloudy lenses with artificial ones to help mainly elderly people to see clear again or recreate the retina, which can be necessary for people suffering from retinitis pigmentosa, by an electronic sensor which is implanted in the eye and replaces the photoreceptor cells, that have been destroyed due to the disease. But it can’t restore the sight entirely, especially if the patient is already completely blind.
Source: Sputnik International
“Sometimes we just have to change our point of view to find a solution – and to see clear.” This idea might be the key of success of Dr John S. Pezaris, who will speak at XPOMET© on March 23. Originally being an engineer, he became a neuroscientist at Harvard Medical School because of his passion for vision. This combination is definitely a reason for his different way of thinking – as his approach is: “It’s the sensors who’ve gone bad, maybe we can fix them.”
Together with Dr. R. Clay Reid, who holds not only a PhD but also B.S. degrees in Mathematics, Physics and Philosophy and therefore is mixed-skilled as well, Pezaris founded the Visual Prosthesis Laboratory on the MGH Boston campus, which is developing a device-based therapy to correct total vision loss due to the above-named diseases. These have in common that the eyes are no longer sensitive to the light, meanwhile the visual part of the brain remains largely intact, but is unable to respond to external stimulation – and that’s where Pezaris and Reid start. They attempt to build an alternate pathway for visual informations to enter the brain by implanting multi-wired electrodes in the lateral geniculate nucleus (LGN) of the thalamus and sending processed information from eyeglass-mounted digital cameras into the visual pathway one stage after the eyes, where the electrodes activate the nerve cells.
Source: Restoring Sight to the Blind
This may sound like science fiction and really it has not been translated into reality yet – at least for humankind. So far Pezaris and his partner inserted the electrodes only into the LGNs of two monkeys. For their experiment the animals sat in a dark room with randomly flashing light spots. The scientists measured which areas of the monkeys’ LGNs had been activated while following the lights and used this data for their next experiment. With the implanted electrodes they stimulated certain areas in the animals’ LGNs – and the monkeys moved their eyes in response to the imagined flashes as they had done to the real ones.
At first the monkeys had to recognize only one spot but in the next step the scientists upped to eight light spots, which can be composed to vertical and horizontal lines – the basis of shapes and patterns.
And to avoid misunderstandings, this detail is important to Pezaris: “No one is talking about restoring normal vision.” It’s about artificial sight. But what does that mean?
To answer this, we have to be a little scientistic first.
Do you know the spots that you can see when you close your eyes? They aren’t generated by actual light but by stimulation of the brain. This kind of perception is called phosphine. So the sight that might appear to the patient when wearing electrode-connected glasses could be compared to a mosaique, built by phosphines. At first it looks like a randomly accumulation of spots, but the brain does a marvelous job by creating an understandable pattern.
Source: Restoring Sight to the Blind
To test the expected results the scientists use VR. In the picture above you can see a screenshot of a movie from this experiment. The image on the left, the “normal” sight, contains about 70.000 pixels. The one on the right is the simulation of artificial sight. It contains only about 700 pixels or rather 500 phosphines. In the screenshot the image isn’t identifiable, but in the moving picture you would recognize that it’s a woman’s face. So the aim of the eye prosthesis is to help blind people to orientate themselves by a crude artificial sight, to identify simple objects – to give them more quality in life.
But why isn’t it reality yet? While the idea is very simple as well as the technological design of the eyeglasses or the camera, “we have to be clever, when we place the electrodes in the brain”, says Pezaris – for obvious reasons. So there is hope for the blind but there is some time to come. It will require many years of concentrated effort and an amount of work to be done before there is even the crudest initial experimental device implanted in a human. But Pezaris and his team are sure that someday eye prosthesis will be used for a blind patient’s treatment on a regular basis. They have already taken many steps: Right now they are designing a system with 1.000 phosphines – doubled the count of phosphines in the upper picture.
“As crazy as it might sound, we’re able to put signals directly into the brain and go from zero to infinity restoring sight to the blind.” (Dr. John S. Pezaris)
Text by Lena Geppert
Source Cover Picture: Techno Crazed