The Composition of Tears and Their Role in Eye Health

Although they may appear to be nothing more than water, our tears are actually quite complex. Your tears contain some salt, as you've tasted when you've had a good cry. But are there other ingredients in tears? Are some tears different from others?

Tears are produced in the lacrimal glands that are in the outer corners of your eyelids with contributing components coming from the meibomian glands (producing oil) and goblet cells within the underside of the lid (producing mucin). These glands produce tears from your blood plasma, selecting some components but not others.

The Composition of Basal Tears and Role in Eye Health

Tears play an important role in keeping us healthy. Tears keep the surface of our eyeballs clean and moist and help protect our eyes from damage. Tears are made of mucus, water, and oil, and each component plays a role in the eye.

• Mucus coats the surface of the eye and helps bind the tear layer to the eye. Without a healthy mucus layer, dry spots may form on the cornea, the clear, dome-like structure on the front of the eye.
• The water saline solution contains various vitamins and minerals vital to normal cell function. These nutrients are important for keeping the epithelium (top layer of cells on the surface of the eye) healthy and functioning normally.
• The oil of the tear film prevents evaporation of the tears. If the oil component is not normal, the tears evaporate too quickly. Some people don't make enough oil (or sometimes too much oil), resulting in dry eyes.

Our tears also contain natural antibiotics called lysozymes. Lysozymes help to keep the surface of the eye healthy by fighting off bacteria and viruses.

Reflex Tears From Irritants

When your eye is irritated, it produces reflex tears to wash out the irritants. You've probably shed a few tears when chopping onions or when you get dust in your eyes.

Emotional Tears

The tears you shed when overcome with emotions have a higher protein content than the tears shed from irritants. Emotional tears have been found to have more hormones, including prolactin, adrenocorticotropic hormone, and leucine enkephalin.

Tears When You Sleep

When you sleep, your glands add less water and protein to your tears, and they increase the number of antibodies present, while infection-fighting cells also migrate to the conjunctival sac.

Tears as You Age

As you age, you can expect to produce fewer tears by volume, and the proteins in your tears also decrease. These changes can lead to developing dry eyes.