Grasshopper's eyelids started doing that a few years ago when she was around ten - it does seem strange for a kitten. Hopper's is in good health, even for an older kitty, and her eyelids still just barely show, as opposed to being completely retracted. Dadcat checked her vitals at the time, and we do annual physicals, with everything OK.
I agree with other posters, have her checked to be safe. We think its environmental, like my dust allergies. This might be an explanation, depending on where you live, if your kitty is indoors only, etc. Hope she is OK!!!!!!!!