Since its first applications in ocular surface squamous neoplasia and dry eye syndrome, [1,2] the use of impression cytology has expanded to include the staging of conjunctival squamous metaplasia, [3,4] diagnosis of ocular surface squamous neoplasia, [5-11] and follow-up of ocular surface squamous neoplasia after topical mitomycin-C, [10] limbal stem-cell deficiency, [12,13] specific viral infections, [14-16] vitamin A deficiency, [17,18] epithelial cell storage disorders, [19] allergic disorders, [19] conjunctival melanosis and malignant melanoma, [20] and psoriasis [21]. The technique has the additional advantage of preserving limbal stem cells, which occur in the basal layer of the limbal epithelium and are responsible for renewal of the corneal epithelium throughout life. Since ocular surface squamous neoplasia preferentially involves the limbus, limbal stem cells are potentially reduced in number with each surgical biopsy. The progressive loss of limbal stem cells results in limbal stem-cell deficiency, conjunctivalization of the cornea with corneal opacity. Thus, impression cytology offers a safer alternative to diagnosis than repeated biopsies.