S. R. Faruqi:

'Knot' is used as a simile for heart. Moving beyond this, he has created an entirely new theme. The idiom aa;Nkho;N me;N jaan a;Taknaa , 'for the life to get stuck in the eyes', is used when there would be an intense longing to see, and the imminence of death. The longing for sight is like a single knot that does not come open. This knot is in the heart, which itself is a knot. Then, this knot within a knot came and got stuck in the eyes.

If the longing for sight had emerged, then one knot would have opened. Then from the opening of this knot, the constrictedness of the heart too would have been removed (that is, the heart would no longer have had the semblance of a knot). But since our heart, in which is the knot of the longing for sight, has gotten stuck in the eyes in the form of the life ( jii can mean 'life', and also 'heart'), then when the longing for sight would emerge, then the life too would emerge. That is, to see the beloved would be something like death.

On the other hand, when the life would emerge, only then the longing for sight too would emerge. That is, as long as we're alive we won't be vouchsafed a sight of the beloved, and the longing for sight has become so mixed with the life that it will only go when life goes.

Another meaning is that just as the longing for sight has passed into the heart in the form of a knot, in the same way our life too has become a knot and gotten stuck in the eyes. To construe the eyes as equal to the whole life is fine, because a powerful 'proof' of it is present: that in the eyes there's the longing for sight, and it will emerge only when life too emerges.

FWP:

SETS == A,B
MOTIFS == EYES; GAZE
NAMES
TERMS == CONNECTION; PROOF

This is an 'A,B' verse, with its two lines consisting of two grammatically and metaphorically independent statements. The parallel-looking beginning phrases tempt us to juxtapose the lines-- but how, exactly? SRF demonstrates several ways, and one can ring the changes even further (cause and effect, and if so which way? two aspects of the same condition? two similar situations? two opposite situations? a single situation?).

That second line is, to my mind, a real weakness. As SRF observes, in ghazal convention the lover's tangled, troubled, convoluted heart is a 'knot'. So what does it mean to have in the heart another knot, that of the 'longing for sight'? Is it a knot inside a knot? Does the one knot somehow subsume the other? It's the sort of metaphor that defeats the visualizing imagination and becomes purely abstract. We can put up with this if the result is highly rewarding, compelling, mesmerizing. But in this case, the lack of any deep, truly enjoyable connection between the imagery patterns of the two lines means that we don't get nearly enough of a reward to make the effort worthwhile. (SRF gives the verse more credit for its originality than I do.)

This is the kind of thing that Ghalib was very fond of in his youthful, wildly experimental days. Here's an apposite example, from among his unpublished ghazals:

G{190,11x}.