Purpose To increase sensitivity of impression cytology (IC) for the diagnosis of conjunctival intraepithelial neoplasia (CIN) by three repeated applications of IC.

Methods This study included 35 eyes with a clinical diagnosis of CIN and 6 eyes with pinguecula as control. All eyes received IC by three consecutive applications of the cellulose acetate filter paper. All eyes in the CIN group had subsequent surgical excision with histopathological evaluation. The sensitivity of each application of IC for the diagnosis of CIN was determined.

Results In the control group, all IC specimens were negative for CIN. In the CIN group, with positive histopathology in all cases, the first IC was positive in 17 eyes (56.7%), showed atypical squamous cells indefinite for dysplasia (ASCID) in 8 (26.7%) and was negative in 5 (16.6%). The second application was positive in 25 eyes (83.3%), showed ASCID in 3 (10%) and was negative in 2 (6.7%). The third application was positive in 26 eyes (87.7%), showed ASCID in 3 (10%) and was negative in 1 (3.3%). The second application resulted in a statistically significant higher positive yield than the first application (p=0.009), with no significant difference between the second and the third applications (p=0.12).

Conclusion Consecutive repeated applications of filter paper significantly increased the diagnostic sensitivity of IC for the diagnosis of CIN.