Try changing your eye drops.
There might be a viscosity level enough to keep them from slipping.
Other than that, try changing the solution that the contacts rest in, they may have a slightly different pH that makes them "crawl" around the eye, hence the drifting.
If the pH is more dissimilar, then it will be like oil resting on water.
If the pH is more alike, then it will probably cling better.

Just thoughts, from the son of a chemistry major, with a heavy dose of biochem.



:M