How do tears work?

When we blink, a film of tears spreads over the eye and keeps the surface of the eye smooth and clear. This tear film is important for good vision.

The tear film is made of three layers:

• An oily layer
• A watery layer
• A mucus layer

The oily layer is the outermost layer of the tear film. It makes the tear surface smooth and keeps tears from drying up too quickly. This layer is produced in the meibomian glands of the eye.

The watery layer is the middle layer of the tear film. It makes up most of what we see as tears. This layer cleans the eye and washes away particles that do not belong in the eye. This layer is produced by the lacrimal glands in the eyelids.

The mucus layer is the innermost layer of the tear film. It helps spread the watery layer over the eye’s surface, keeping it moist. Without mucus, tears would not stick to the eye. Mucus is produced by the conjunctiva. Conjunctiva is the clear tissue covering the white of your eye and inside your eyelids.

Normally, our eyes constantly make tears to stay moist. If the eyes are irritated, or when a person cries, the eyes make a lot of tears. But, sometimes the eyes don’t make enough tears or something affects one or more layers of the tear film. In such cases, we end up with dry eyes.