In John 8, Jesus is in the treasury of the temple in Jerusalem during the Feast of the Tabernacle. Jesus had just brought the truth to light for a woman caught in the act of adultery and for the seemingly righteous religious leaders who had caught her. Drawing on this teachable moment, Jesus claims to be the light of the world.
What immediately follows this discourse is an encounter Jesus has with a man who has been born blind. This man has never seen light. The irony of the story is that the blind man is the one who sees reality because he believes Jesus is the light of the world.