Got minor facelift and began wearing wigs in the early 90s?
If you see him for example in Lethal Weapon 2, you can notice advanced baldness and his face looks 'normal'.
A couple of years later (Goodfellas / Cousin Vinny), you notice that there is absolutely no baldness in some movies and his face, around the eyes seems to have been 'pulled back'.
So I'm suspecting a wig and minor plastic surgery?
Just something I noticed watching some of his movies from that era... found it a bit distracting, that's all.