For "makes the bones fat," the marginal reference reads, "makes the bones healthy."
"The light of the eyes" - One might think that the psalmist refers the light in one's own eyes, but in this case, it is not. It is the light in another's eyes. What would we consider to be the light in another person's eyes within the context of this verse? It has to be something that the person is joyous, happy, enthused, encouraged about. He loves whatever they heard, and when he brings this news, one can see the light in his eyes. What does it do to the observer? It picks him up, and it is good for a person to be in such a situation. This verse illustrates how an environment can produce positive effects.
We know from our own life experiences that this is so. If we step into a room charged with anger, depression, bitterness, envy, jealousy, prideful gossip, or suspicion, what happens to us? We sense it or discern it immediately. We may become defensive and want to leave just as fast as we can.
Conversely, instead of entering a room charged with a negative attitude, perhaps we encounter a positive one. It pulls us toward it and makes us want to join and enjoy the benefits of such a positive, uplifting, and good spirit.
John W. Ritenbaugh
The Holy Spirit and the Trinity (Part 4)