The narrator is a Dubliner in Dubliners by James Joyce, the story collection "Araby" is included in. Just as the street and neighborhood is described, indirectly or figuratively, as blind, so is the narrator. He becomes obsessed with an illusion, a combination of his idealistic view of Mangan's sister, and his idealistic view of his relationship with Mangan's sister.
He suffers terribly, like an adoliescent will, in the days preceeding his trip to buy her a gift at the traveling bazaar, Araby. He neglects his studies and can think of nothing else. He is blind to the truth that Mangan's sister hardly even knows he exists, and that they do not really have much of a relationship.
The combination of the bazaar being closed (for the most part), the trivial, senseless flirting by the workers he overhears, the rudeness of the worker who asks him if he needs anything, and something about the few items for sale, leads him to sight, figuratively. He realizes how silly he's been, that he's been infatuated with and controlled by an illusion. He states his epiphany in the final lines of the story:
Gazing up into the darkness I saw myself as a creature driven and derided by vanity; and my eyes burned with anguish and anger.
Notice the reference to the eyes. His eyes figuratively fool him into falling for an illusion. Now, they are figuratively opened.