What is the Tear Film?

We normally think of tears as the excess moisture that overflows from our eyes when we cry or when our eyes "water". However, a thin film of tears must constantly be produced and washed over our eyes to keep them moist. This type of tears is referred to as the tear film.

The tear film is the body's natural mechanism for protecting the surface of the eye from the irritating effects of dirt, dust, and other airborne particles, as well as from infection. The tear film helps to create a smooth surface so vision stays clear and undistorted, and eyes stay lubricated and comfortable.

The tear film has three main components: lipid, aqueous, and mucin. Lipids form an oily layer on the outside of the tear film and help slow down evaporation of tears.

The largest portion of the tear film is made up of the aqueous (watery part) with different types and concentrations of mucins (sticky proteins) throughout. The thickest concentration of mucins is at the eye's surface. Since the eye's surface is naturally water repellant, the mucins are needed to create a water attracting surface so the aqueous part will spread over the eye.