Evaluation of ocular surface disorders: a new diagnostic tool based on impression cytology and confocal laser scanning microscopy

Aim To provide a new tool for the evaluation of altered ocular surfaces by using a combination of impression cytology, laser scanning confocal microscopy and advanced image analysis. Methods The expression of keratin 3 (K3), keratin 12 (K12), keratin 19 (K19) and mucin 1 (MUC1) was analysed by immunofluorescence on both histological sections of nine corneoscleral buttons from normal donors comprising conjunctiva, limbus and cornea and impression cytology specimens from six healthy normal subjects (12 eyes) and 12 patients with chronic ocular surface disorders. Levels of fluorescence expression of the different markers were quantified through quantitative fluorescence immunohistochemistry (Q-FIHC). Results Impression cytology specimens from normal and diseased ocular surfaces showed distinct expression patterns for K12 and MUC1. Healthy corneas expressed only K12 (but not MUC1), while conjunctivalised corneas from patients with limbal stem cell deficiency (LSCD) were characterised by the presence of MUC1 and the disappearance of K12. Similar clear-cut results were not seen with the K3/K19 markers, which showed lack of specificity and overlapping signals in cornea and conjunctiva impression cytology specimens. Conclusions The ability of K12 and of the antibody against MUC1 to discriminate clearly between limbus/cornea and conjunctiva in impression cytology specimens could become a valuable diagnostic tool for ophthalmologists in order to evaluate alterations of the ocular surface and the grading of LSCD.