What is the main supply of oxygen to the corneal epithelium derived from?

The main supply of oxygen to the corneal epithelium primarily comes from the tear film. The tear film creates a thin layer of fluid that sits on the surface of the cornea, allowing for gas exchange. This is crucial because the corneal epithelium is avascular (lacking blood vessels), so it cannot receive oxygen directly through blood circulation. The tear film facilitates the process of diffusion, allowing oxygen present in the atmosphere to dissolve in the tear film and then pass through to the epithelial cells of the cornea.

In addition to atmospheric oxygen supplied by the tear film, during situations where the eye is closed, such as during sleep, the oxygen can also come from the underlying aqueous humor. However, under normal conditions of open-eye functionality, the tear film plays a significant role in providing the necessary oxygen to maintain corneal health and clarity.

In summary, the tear film is crucial for ensuring that the corneal epithelium receives adequate oxygen, which is essential for maintaining its metabolic functions and overall health.