I was reading a post on 'Starts With a Bang' where they were discussing the merits of Dark Matter over MOND and there was a picture of a large spiral galaxy with many starts in the field behind it. What struck me was that the background seemed to be in perfect clarity. There was no distortion in the field of stars in the background. However, Spiral Galaxies must have incredibly huge Dark Matter Halos in order to have such flat velocity profiles. I believe I read somewhere that the Milky Way is supposed to have 6 to 8 times the visible mass in its halo. Is there any evidence of Spiral Galaxies acting as Gravity Lenses proportional to the amount of Black Matter needed to flatten the velocity profiles?