S. R. Faruqi:

The verse is seemingly simple, but in it is concealed the point that 'a madman has no grief'-- that is, the intensity of madness and wildness causes one to forget things like grief and weeping. Here, the situation is that the dust is flying around his face because of madness (that is, the dust that he had flung up in madness has left traces on his face as well; or his face has become entirely lightless and desolate)-- but nevertheless, the intensity of his sorrow is such that from his eyes tears of blood are dripping. The intensity of the sorrow was so deep that not even the intensity of madness was able to diminish it.

FWP:

SETS == GROTESQUERIE
MOTIFS == EYES; MADNESS
NAMES
TERMS

Well, it's a distasteful and unfortunately very emphatic, very graphic vision-- a dusty face, with bloody tears flowing over it and making muddy tracks through the dust. I know, I know, there are many reasons why this grotesquerie is set up as it is, and how it can be said to 'work' in the ghazal universe. I'm just registering a personal shudder of dislike. If I did my own intikhab, this verse wouldn't be in it.

But why ;xaak sii , 'something dust-ish', instead of just dust? SRF takes the meaning to be simply 'dust'; but then it looks as though Mir has thrown in the sii only for padding. If we give Mir more credit, we could imagine that the mad lover is so crazed that he has trouble even recognizing dust-- dust that probably he himself has been flinging around. We could also imagine that he's in a kind of half-fainting condition, seeing spots before his eyes or a haze before his face and thinking that the world (or at least, his world) is pervaded by dustiness.

Perhaps then the second line expresses relief and pride: even under the most adverse conditions his faithful eyes still keep functioning, dripping blood, cutting through the 'dust', and doing their lover-like duty. Or at least, they have been doing this 'up to now'-- which opens up ominous prospects for the future.