Do you mean "High Index" lenses? ... I have strong prescriptions of -9.x and -11.x and I have had 1.66 index lenses. I've always noted to doctors light sources move around or float around alot with the lenses. I haven't necessarily noticed a difference with contacts (but I did see sharper with hard contacts) but my eyes cannot tolerate hard or soft lenses.

I have tried even higher index lenses, but anything above 1.66 and the distortions and optical aberrations get too annoying ...