Which layer of the tear film is responsible for providing hydration and lubrication?

The aqueous layer of the tear film is primarily responsible for providing hydration and lubrication to the ocular surface. This middle layer contains a significant amount of water along with electrolytes, proteins, and various nutrients essential for the health and function of the cornea and conjunctiva. The hydration from the aqueous layer helps maintain the osmotic balance of the tear film and protects the eye from dryness, while also assisting in the smooth movement of the eyelid across the surface when blinking.

While the oil layer plays a crucial role in reducing evaporation of the tear film, and the mucin layer helps to anchor the tears to the surface of the eye and improve spreading, it is the aqueous layer that directly provides the necessary hydration and lubrication critical for the health of the eye and comfort of the patient. Thus, the aqueous layer is fundamentally important in maintaining the integrity of the tear film and supporting overall ocular health.