He looked up and said, "I see people; they look like trees walking around." Once more Jesus put his hands on the man's eyes. Then his eyes were opened, his sight was restored, and he saw everything clearly. (Mark 8:24-25)
... [T]he real story of this miracle is that it is really two miracles in one, or more accurately, it is a two-stage miracle. After the first stage, the man can see but his vision is very blurry. Only when Jesus touches him a second time can he see clearly. All the Bible commentators remark on this because there is nothing else like it in the gospels. We know that everything Jesus did, he did for a purpose. He never did "random" miracles or simply performed miracles for no reason at all. So there must be some purpose in the two-stage healing of this blind man. But the text merely relates the story. It doesn't explain the deeper meaning. And that brings us back to the question, "What's going on here?"
... If you go back to the beginning of Mark 8, you have the miracle of the feeding of the 4000 (Mark 8:1-10). Immediately afterwards the Pharisees came to argue with him (Mark 8:11-12). After Jesus and the disciples got into a boat, he warned them to beware of the leaven of the Pharisees (Mark 8:15). Leaven is another word for the yeast necessary for baking bread, but in this case it refers to the false teaching of the Pharisees. But the disciples thought he was talking about literal bread. Jesus then rebuked the disciples by saying, "Having eyes do you not see, and having ears do you not hear? And do you not remember?" (Mark 8:18). Or we could paraphrase it this way:
"How can you be so blind after having been with me so long? Don't you understand anything I'm saying?"
... Cloudy spiritual vision afflicts every Christian to some degree. None of us sees as clearly as we would like for now we see through a glass darkly.
... That's what this blind man experienced. When he was partially healed, he saw men as trees walking. No one sees life with perfect clarity. All of us have spiritual nearsightedness to one degree or another.