End the darkness
He is writing here not of a physical blindness, but of a spiritual blindness: most especially the blindness of hate.
We all know people like that and we even sometimes get that way ourselves: hate, resentment, and anger causes us not only to ignore the good in other people, but also closes us to the light of God. We become fixated on our own feelings and perceptions. We actually may become unconsciously afraid of being challenged by the truth: the truth of Christ and the full truth about others.
We need to pull out of the darkness of negative emotions we may have piled up around ourselves and let the light and the truth of our Lord and Savior Jesus Christ shine.