I never saw such lovely eyes, To have no light within them. To have no thought, no sweet surprise, No tears to ever dim them.
I never saw such lovely eyes, So large, so round, and tender, With lashes lifted to the skies, But blind — may Heaven defend her !
A speaker looks at someone whose eyes are perfectly lovely, large, round, tender, framed by lashes that seem to reach toward the sky, and then realizes they are blind. The poem builds on that sudden turn. For the first three lines of each stanza we're admiring, and then comes the catch: nothing is behind the beauty, no light, no thought, no surprise. Even the tears that would normally dim eyes are missing, which is an oddly tender detail, since it suggests the person is spared sorrow along with everything else.
The speaker's feeling is a mix of admiration and pity, ending in a quiet prayer: "may Heaven defend her." Notice that the second stanza repeats the opening line almost word for word. That repetition works like a double take, as if the speaker keeps returning to the sight and cannot get past it. The mood is gentle, wistful, and protective rather than despairing.