The investigators will conduct a randomized, investigator-blind, interventinal study on 28 subjects. Each subject will apply a benzalkonium-chloride (BAK) preserved eye drop (Xalatan) in one eye and a preservative-free (PF) eye drop (Monoprost) in the other for 3 months. Which eye gets which treatment is randomized. Before and after treatment a conjunctival print will be made and the effect of the eye drops on goblet cell density will be evaluated along with effect on the intraocular pressure.
a randomized, investigator-blind, interventinal study will compare the effect of benzalkonium-chloride (BAK) preserved and preservative-free (PF) eye drops on conjunctival goblet cells.