A new hypothesis on tear film stability.

Classically, the stability of the lacrimal film is due to the surfacing of the epithelial surface by the mucus produced by the goblet cells. However, there are many objections to this hypothesis. Deducing from electron microscopy of the epithelial cells, which shows vesicles in the superficial layer and glycocalix threads on the microvilli and other clinical facts, we think that the surfacing agent is not mucus but glycocalix. The disappearance of goblet cells during sicca syndrome is not the cause but the result of the dryness. Epithelial cell integrity is essential for the stability of the tear film and therapeutics must aim at regenerating these cells rather than only replacing the lacrimal film by tear substitute.