How many layers comprise the tear layer?

The tear film consists of three distinct layers: the lipid layer, the aqueous layer, and the mucin layer.

The lipid layer is the outermost layer and serves to reduce evaporation of the underlying aqueous layer and to provide a smooth surface for light refraction. The aqueous layer, which is the middle layer, contains water along with electrolytes, proteins, and other substances that nourish the cornea and provide lubrication. The mucin layer, which is the innermost layer, helps the tears adhere to the surface of the eye and provides a smooth and even surface for the tear film to spread over the cornea.

Understanding the composition of the tear film is vital in ophthalmology, as each layer plays an important role in maintaining eye health and comfort. Recognizing that there are three layers provides a foundational insight into how tears function and their significance in ocular physiology.