You are asking about Matthew 6:22: "The eye is the lamp of the body. So, if your eye is sound, your whole body will be full of light."
The eye—singular—is the lamp of the body. What Jesus calls the eye is the source of light, of energy. It is the power in which we place our faith.
When we rely on the evidence of our senses—our double eyes of mortal sight—we are drawing from an energy of duality. We are believing sensory evidence that insists we are separate from each other and from God. When our eye is single, we are relying on the unified light of the Christ Presence within us. We recognize One Presence, One Power. We see clearly, because we see only God in expression wherever we look.