National Contact Lens Examiners (NCLE) Practice Exam

The lipid layer of the tear film plays a crucial role in preventing evaporation of the underlying aqueous layer. This outermost layer consists of various lipids that create a hydrophobic barrier, significantly reducing the rate at which moisture escapes from the tear film. By maintaining this barrier, the lipid layer is essential for keeping the eyes adequately lubricated, which is important for comfort and overall eye health.

The other layers of the tear film serve different functions. The aqueous layer provides hydration and supplies nutrients to the corneal surface while also containing antimicrobial proteins that help protect the eyes from pathogens. The mucin layer, on the other hand, aids in the dispersion of the tear film across the surface of the eye and helps ensure that the tears adhere properly to the cornea. The vitreous layer is actually not part of the tear film; it is a gel-like substance in the eye that helps maintain its shape.

In summary, it is the lipid layer that is primarily responsible for preventing evaporation and thus plays a vital role in maintaining tear film stability and eye health.