Thomas Aquinas Commentary Lamentations 3:49-51

"Mine eye poureth down, and ceaseth not, without any intermission, Till Jehovah look down, and behold from heaven. Mine eye affecteth my soul, because of all the daughters of my city." — Lamentations 3:49-51 (ASV)

Here the compassion of the prophet is presented.

First, regarding external mourning: his eye is afflicted by crying; it has not been quieted from tears and finds no rest from the tribulations of the people. Let my eyes shed tears, for a voice of wailing is heard out of Zion (Jeremiah 9:19–20).

The end of this mourning is till God regarded him with an eye of mercy. Because he has looked forth from his high sanctuary (Psalms 101:20).

Second, regarding the spur of inner pain: my eye sees the pillaging of the earth, and this sight has wasted my soul by depriving it of joy. Alternatively, it means that through weeping, he has pulled all the pain out of his heart.