Background: The present knowledge about ocular mucins is presented.
Results: Mucins are glycoproteins of high polymer structure. Following the classification of the Human Gene Mapping Committee, they are subdivided in MUC1-9. They are an important component of the tear film and are found in conjunctival and corneal ocular surface epithelia. The mucins of the ocular surface epithelia belong to MUC1, MUC4 and MUC5AC. The existence of MUC2 is in doubt and controversial in the scientific literature. However, a mucin-associated peptide that belongs to the group of trefoil peptides was found in the goblet cells. It is the intestinal trefoil factor (ITF) that seems to interact with mucins during reepithelization in other organs and in cell culture. Unclear is the significance of oligosaccharid structures of mucins like Tn and sialosyl-Tn, which are found in the surface epithelia of the eye.
Conclusion: Further investigation will be necessary to answer many open questions concerning the existence, significance and function of ocular mucins.