Black color in refractions when trying to create eye "wet layer" - Vray 4 update 2

[ilmelovfx]

Hi all,
I don't know if this is a bug with Update 2 or my mistake, but as far as I can recall I did some time back and all worked nicely...
I'm trying to do a "wet layer" for the eyes of a creature I'm rendering in Vray. The geometry as you can see in the pictures attached is a simple tube sculpted in ZBrush, imported in Max, and rendered as a standard glass VRayMat with Vray 4 Update 2.
The problem is it turns out all black.... I tried bumping up the ray depth (up to 15) and checked polygon normals orientation, but nothing changes... I dont know what to do...
The face of the creature is a FastSSS2 mat, the eyes are the usual inner sphere FastSSS2 and outer sphere glass VrayMat... Both the skin and the inner eye sphere have vraydisplacement modifier...
I disabled "cast shadow" in both the outer eye glass sphere and in this wet layer tube geo, because it's my usual way to do this and I think shadows dont do much difference in that case and just darken a bit the object behind.
If I render it separeted from the face and eyes of the creature (all the other settings and geometry are the same) renders ok... (see pictures attached).
Can someone please give me some advice or point me to some links and pages with useful info about how to correctly do this and solve the issue?

[ilmelovfx]

Ok I managed to remove the black color in the refractions of the wet layer by removing a VrayDirt map I used in the face skin material (FastSSS2). I plugged the dirt material because I liked a darkened color in the wrinkles in the skin.
So my question is now: is it possible to use a VrayDirt map in the sub surface color of the FastSSS2 material? It produces nice results but introduces artifacts (in this case, the black color in refractions). Is there a correct procedure?
Thanks

[M.Max]

You might try include/exclude and /or consider same object only options under Vray dirt map to avoid this

[ilmelovfx]

Thank you very much M.Max, I didn't consider that option (same object only) in Vray Dirt map! Now it works much better!