Hi there! I haven’t tried scrying before but I know that others have & found a couple of topics in the forum regarding using them, maybe they would help with some of the questions.
As far as the eye issues… (I have lattice degeneration, astigmatism, and myopia) If I am wearing my corrective contacts then no, I don’t have to take them out… but for reference, I am softening my gaze or demeanor for energy field reasons or to see auras or get a feel for the person/place.
Mirror Gazing to Contact the Spirit of a Deceased Loved One
I hope someone else has some better answers for you, but those may have some answers within the replies. 