Here's an exerpt from a magazine article I wrote (it's not on this exact subject, but on a similar one):
“And Jesus took the blind man by the hand…and when He put His hands upon him, He asked him if he saw anything. And he looked up and said, “I see men looking like trees walking.” Mark, 8:24
The Miracle of Sight
“Seeing is believing,” according to the aphorism. But William Moyneux, whose wife was blind, asked philosopher John Locke: “Suppose a man was born blind and taught by touch to distinguish between a cube and a sphere. If his vision was restored, could he distinguish which was which before touching them?”
In several rare medical cases, the blind actually have had their vision restored. As reported by Oliver Sachs in An Anthropologist on Mars, the adjustment has not always been easy. H.S., a patient who received a corneal transplant after 22 years of blindness reported:
During the first weeks I had no appreciation of depth or distance; street lights were luminous stains stuck to the window panes, and the corridors of the hospitals were black holes…. Nor was it possible for me to count my own five fingers… it was not possible to pass from one to the other while counting.
All of the newly sighted have difficulty adjusting. S.B., another individual who had recovered his sight was always struck by how objects changed in appearance from different perspectives. For those not accustomed to seeing, this flux of appearances is not anchored to the world of objects – to space.
The infant learns to coordinate the impulses sent to the brain by his optic nerve with images sent by his sense of touch by batting a mobile around in his crib. As adults, we have no memory of this process of learning how to see. But Mark’s version of Jesus restoring the blind man’s sight is in remarkable agreement with the medical records. When Jesus first restores the man’s sight, the man can see, but cannot distinguish between men and trees. So Jesus, “put His hands on his eyes again… and he saw every man clearly.” The miracle was actually two-fold – restoring physical sight and providing enlightenment as to how to interpret it.
(lest the atheists on this board attack the notion of "miracles" let me assure them that I am not commenting on the historical accuracy of the story, merely on its artisitic merit in confoming to scientific facts not widely known when the story was written.)