Mark 8:22–26 records Jesus' healing of a blind man at Bethsaida. When the villagers brought the man to Jesus, Jesus took him outside the town, spit on the man's eyes, laid his hands on him, and asked him if he could see anything. The man answered, "I see men as trees, walking." Jesus then put his hands on the man's eyes again and made him look up, and with that the man could see clearly and normally. Jesus sent the man home, instructing him not to tell anyone back in the town. This account contains several remarkable details and raises interesting questions.
First, and most extraordinary, is the line "I see men as trees, walking." What are we to make of this sole statement made by the blind man? Interestingly, it is scientifically sound. Similar occurrences have resulted in strikingly similar descriptions of partially restored sight. Modern ophthalmology has learned that when eyesight is restored to people who have been blind for an extended amount of time, those people must relearn to assemble the data in order for their brain to make sense of it all. It takes time for the brain to get used to processing visual data. Thus a tree or a man at first does not look like a single, integrated unit, but only like a set of disjointed parts, merging together.
A recent book by Oliver Sacks reports a case study of a man named Virgil, who seems to have had just this experience.