Optics 500 Practice Exam 2025 - Free Optics Practice Questions and Study Guide

The middle layer of the tear film is known as the aqueous layer. This layer plays a crucial role in maintaining ocular surface health by providing moisture, delivering nutrients to the corneal cells, and serving as a medium for waste removal. It makes up a significant portion of the tear film and is primarily composed of water, along with electrolytes, proteins, and other substances that help protect the eye against infection and maintain overall eye comfort. Understanding the functions and composition of the aqueous layer is essential for comprehending how tears contribute to eye health and the maintenance of clear vision.

The outer layer serves primarily as a protective barrier, while the inner layer would be in direct contact with the eye's surface, potentially including mucin and lipid components. Moreover, while the term "protective layer" could imply a role played by tears, it does not accurately describe the composition or primary function of the aqueous layer. This helps clarify the specific nomenclature and structure of the tear film for a more comprehensive understanding of its elements.