Which of the following is NOT a function of the precorneal tear film?

The precorneal tear film is an essential component of eye health and serves several important functions. One key role is to flush away cellular debris, which helps maintain a clear optical surface and prevents infections. It also provides nutrition to the cornea, which lacks its own blood supply and relies on the tear film for oxygen and essential nutrients. Additionally, the tear film acts as a refracting medium, contributing to the overall optical properties of the eye by helping to focus light onto the retina.

In contrast, regulating eye pressure is not a primary function of the precorneal tear film. Eye pressure, or intraocular pressure, is primarily maintained by the production and drainage of aqueous humor, which is produced by the ciliary body and fills the anterior chamber of the eye. Therefore, while the tear film is critical for surface health and vision, it does not directly regulate eye pressure. This distinction clarifies why the correct answer is the option regarding eye pressure.