The Day of Atonement pictures a time when Satan will be bound with a great chain and cast into a bottomless pit for 1000 years. At that time, all of mankind who have lived in spiritual blindness will have their eyes opened to the light of the truth (Revelation 20:1-3).
The people represented are coming out of the great tribulation, a time of unparalleled suffering and are pictured as physically blind. Those in front are having their eyes opened to the light now that Satan is removed. The painting also serves as a metaphor for the work of the church, opening the eyes of those who have been deceived to the truth of God.