In a modern, cosmopolitan city, a driver stops in traffic. He has gone blind, but he's not in the dark. All he can see is white light. The man who offers to drive him home and then steals his car suffers a similar fate. The ophthalmologist he visits (Mark Ruffalo) is stumped. And then he, too, is infected.
The film settles in behind the bars of the long-closed asylum where the wife keeps her secret and becomes caretaker and nurse to the newly blind. People whose lives crossed don't realize it. A hooker is held with a pharmacist she insulted, the thief with the man whose car he stole, the patients of the doctor's medical practice, all locked up on pain of death by a paranoid military working on behalf of a paranoid nation.
The blind stumble about, abandon clothes and live in their own filth. The husband-wife dynamic is reversed as he becomes totally dependent on her. They have no idea what's happening in the nation at large.
Eventually, competing wards form into a Lord of the Flies as the strong and thug-like, led by a bartender ( Gael Garcia Bernal), prey on the rest, holding the dwindling food supplies hostage.
Meirrelles (The Constant Gardener, City of God), working from a José Saramago novel, plays around with light and sight, blurring or over-saturating his images, cutting off heads in conversations (think The Diving Bell and the Butterfly). He creates one of the most vivid screen end-of-the-world dystopias of recent memory.
But aside from a few cracks about the wife as "a leader with vision," there doesn't seem to be much point. There's no moral to the story, save the one we can all guess when we hear this film's plot. When civilization breaks down, humanity goes out the window. You don't need 20/20 vision to see that.