Besides the oxygen and moisture, what is another key role of the precorneal tear film?

The precorneal tear film plays several vital roles in maintaining ocular health, with lubrication being a primary function. This thin layer of tears coats the surface of the eye, ensuring smooth movement of the eyelids during blinking, which reduces friction. This lubrication is essential for preventing irritation and maintaining comfort for the eye, which is particularly important for visual acuity and overall eye health.

While the other options present functions that may have some relevance to the eye, they do not accurately describe a key role of the precorneal tear film. For example, while the tear film does contribute to the prevention of infection through its components, lubrication is its most direct and primary role during eye movement and daily functions. Thus, focusing on the lubricating function emphasizes the importance of the tear film in the overall maintenance of eye health and comfort.