The epithelial surface

Many of the important functions of the corneal epithelium are influenced by the substances in the precorneal tear film. The main functions of the epithelial surface are to:

  • block the passage of foreign material such as dust, water and bacteria into the eye and other layers of the cornea
  • provide a smooth surface that absorbs oxygen and cell nutrients from tears, then distributes these nutrients to the rest of the cornea

The epithelium is lubricated by the precorneal tear film. The tear film also constitutes one of the refracting surfaces of the eye and must be smooth in order to refract light in a systemic manner.

The epithelium is naturally hydrophobic (water repelling). Therefore, to allow the aqueous layer of the tear film to remain on the corneal surface and prevent it from sliding off, a hydrophilic (water attracting) mucus layer adheres to the epithelium and acts as a bridge between the two surfaces.

The mucus layer is thought to be anchored to the epithelial surface by specific binding between IgA and mucus, and IgA and epithelium. 

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