impression cytology in different types of contact lens users

this study compared tear function tests and cytologic changes on the conjunctival surface in asymptomatic patients wearing contact lens of different materials. included in this study were 40 eyes wearing daily wear 4 week replacement hydrogel (h) lenses, 32 eyes wearing silicone hydrogel (sih) lenses, 18 eyes wearing rigid gas-permeable (rgp) lenses, and 21 healthy eyes (no lenses) as the control group. epithelial morphology of the conjunctival surface was evaluated, based on nelson classification with conjunctival impression cytology (cic), after the tear break-up time (tbut) and schirmer test were performed. the mean values of the schirmer and tbut tests were significantly higher in the control group than in the other lens groups (p < 0.001). grade 0 was the most frequent cic in the control group (66.7%) and least frequent in the sih lens group (40.6%); grade i was least frequent in the control and rgp groups (33.3%) and most frequent in the sih lens group (40.6%). moreover, grade 2 was most frequent in the sih lens group (18.8%). there was no statistically significant difference in goblet cell densities between the groups (p = 0.462). in addition to the different schirmer and tbut test results between contact lens wearers and healthy non-wearers, some cytologic changes may occur on the ocular surface with direct mechanical effects of contact lenses. this simple and noninvasive technique may be used to evaluate the ocular surface with regard to intolerance to contact lenses.