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More to vision than meets the eye California businessman Mike May recovered his vision after 40 unsighted years. His case is revealing new insights into the neurology of visual development and the process of visual recovery following stem cell and corneal transplantation surgery.
Mr. May, now 49 years old, lost his first eye in an early childhood accident. The second eye became occluded by a dense cataract and thick corneal scarring. An attempted corneal transplantation procedure during his childhood failed. He remained completely blind through early middle age. Four decades after May lost his vision, San Francisco surgeon Daniel Goodman MD performed a stem cell transplantation followed by a corneal graft. The surgery was a success, providing May with a clear cornea. "It was a big surprise to everybody when the bandages came off. I didn't expect to see. I wasn't even thinking about it. I was just thinking they would change the bandages," May said in an interview with EuroTimes. Optically, May's eye was not too bad, capable of providing acuity of at least 20/40. Neurologically however, his visual cortex was providing vision no better than 20/1000. Cases of recovered vision after interrupted childhood visual development are extremely rare. May was contacted by neuroscientist Ione Fine PhD, who conducted a series of objective and subjective evaluations of his visual abilities as he learned to see again. "Mike's case offered a rare chance to learn about the effects of long term deprivation on visual development. I did a literature search to find out what we do about this, and found the answer was almost nothing'! It was an incredible opportunity," said Dr Fine, now at the University of Southern California 's Doheny Eye Institute. She organised functional magnetic resonance imaging (fMRI) studies of May's brain over a series of two months intervals following the surgery. He lay within an MRI scanner, viewing a series of images that were projected onto a screen inside the bore of the magnet. Meanwhile Dr Fine observed which parts of the brain were activated by these visual images. The objective was to determine whether the parts of the brain normally associated with visual perception were activated. "We ended up with a very clear picture of his visual processing. Simple motion processing, or even complex motion sensing, was very good. But his form perception was quite weak. Especially when he would start to integrate parts into whole, or when he tried to recognise objects or faces. Projection into the third dimension was very difficult," she explained.
"There seemed to be a real difference between his ability to process motion and colour compared to his ability to process three dimensional forms. The part of brain responsible for motion processing was normal, but the areas of the brain that were responsible for the identification of objects and face recognition were no longer active," she said. Psychophysical testing also demonstrated the unusual disconnectedness of May's visual perception: "There was a moment when I got a handle on what was going on. I showed him a stationary wire drawing and asked him what it looked like. He described it as a square with extra lines. We then simulated an image of the cube moving in and out of the computer monitor and he burst into laughter and said it was cube going in and out," she recalled. Previous research had already established that motion processing is activated very early in the process of visual development, and that three-dimensional form processing comes in much later. This case suggests, among other things, that plasticity in visual development extends beyond the traditional critical period of amblyopia. May's case also dramatises the difference between seeing and perceiving. In recent months he has adapted to his situation by consciously sorting out the images he sees in order to make sense of them. He is learning to make the most of the visual processing he is capable of. "My processing speed has improved. I am much better at figuring out what an object is and can put together the clues much faster. My library of visual cues has grown tremendously. At the beginning I would see a person and say is that a man or a woman? I would have to look at the hair, the body, the way they walk, and what are they wearing. It would take two or three minutes to analyse six or seven things. Now when I look I know what I'm looking for and where the clues are, so I can create an image much quicker," he explained.
Mike had become extremely well adapted to life as a blind person. He was very active and was quite an avid skier. For a time after recovering his sight, he still preferred to ski with his eyes closed. He has since learned to use his available vision to discern texture and shading differences in the snow as he skis. "Mike uses shading as a cue. We tracked him recently on a task involving innate understanding of shading. When he looks at a mogul he sees what looks like a darker patch of snow and knows that's a mogul'. He doesn't think as we do that the snow is the same colour with shadowing. He sees colour differences and cognitively knows it's a mogul," explained Dr Fine. Dr Fine said she hopes the current work will encourage researchers to focus more on the plasticity of visual development in adults. There is no animal model for this. Only in the past decade have investigators even begun to focus seriously on studying higher level visual processing. "The take home message so far is that plasticity in these areas of the brain is intimately related to their function. It is not something arbitrary. The areas of the brain that process faces and objects don't like being in the dark for 40 years, they constantly need new experience. Plasticity is part of visual development," stressed Dr Fine. Dr Fine reports her research in the September 2003 issue of the journal Nature Neuroscience. Ione Fine PhD
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She noted that while May could see all the images without difficulty, it was almost as if he were living in an abstract painting where there was very little meaning. He appeared to be living in a world of shapes and colours, instead of a world of objects. 