An eye that you treated is the one that turns against you.
What it means
The eye you healed is the one that later looks at you with ill will. The proverb warns that a person you helped may turn against you, and cautions against the ungrateful and the jealous.
Source: Luo (Kenya, Tanzania) oral-tradition proverb — "African Proverb of the Month," February 2003 (afriprov.tangaza.ac.ke)
The source explains it: to warn and create awareness in community members towards jealous and unappreciative people. The wording of the meaning is ours.