His eyes are still functioning, but the brain can't process the incoming data, so things get remapped to areas of the brain responsible for other types of functions.
Actually, as KingMob explains in [1], the mappings are already there in healthy persons as well. This is the "lizard brain" - the original neural pathways transmitting visual information to various subconscious modules that evolved hundreds of millions of years before the relatively new invention of the mammalian cerebral cortex. As evolution rarely throws out anything that works, the archaic modules are still there, functioning, and in this patient's case, only the more recent higher-level capacities were destroyed.
Actually, as KingMob explains in [1], the mappings are already there in healthy persons as well. This is the "lizard brain" - the original neural pathways transmitting visual information to various subconscious modules that evolved hundreds of millions of years before the relatively new invention of the mammalian cerebral cortex. As evolution rarely throws out anything that works, the archaic modules are still there, functioning, and in this patient's case, only the more recent higher-level capacities were destroyed.
[1] http://news.ycombinator.com/item?id=4319700