those meds and your medical problems could certainly be causing dryness. try some over-the-counter lubricant eyedrops or artificial tears if you havent already. not "visine".
about the loss of sight...pituitary tumors can & do cause vision loss...its anybody's guess as to when it will return or even if it will ever return at all. nobody knows and every case is different.
http://www.wiseorb.com/articles-review-478-T-DRY_EYES%3A_THE_PROBLEM_OF_THIS_TIME%2E.htm