When Melinda tries to break the ice with Rachel early in the novel, both girls are looking in the mirror in the girl's bathroom. Melinda thinks, "My contact folds in half under my eyelid. Tears well in my right eye" (9.9).
Aha! The broken glasses, the twisted contact, the fake eye, the blindness – when you find these in a story you can expect characters to undergo drastic changes in vision. Often characters move from unclear to clear vision over the course of the story. This seems to be true of many of the characters in Speak, especially Melinda. When she can see clearly, she's able to make her life clear to the very confused people around her.