Tear Film 101

The tear film has three important layers, each playing a unique role:

• Fatty oils – Keep the tears from evaporating too fast.
• Aqueous fluid – The watery layer that hydrates the eye.
• Mucus – Helps spread tears evenly across the surface. Gross, but essential.

If any of these layers break down or stop working properly, dryness sets in.

What Causes Tear Film Trouble?

A bunch of things can mess with tear film function, such as hormone changes, autoimmune diseases, inflamed eyelid glands, or allergic eye issues. Sometimes the problem is that the eyes just don’t make enough tears. Other times, tears are made—but they evaporate way too fast. Either way, it leads to that scratchy, itchy, uncomfortable feeling.

The Tear Team: Glands and Ducts

The lacrimal glands, located above each eye, are in charge of tear production. Every time the eyelids blink, they swipe tear fluid across the surface of the eye. Any extra fluid drains through tear ducts into the nose (yep, that’s why crying gives you a runny nose).

When There Aren’t Enough Tears

This condition has a fancy name: keratoconjunctivitis sicca (bless you). It means the eyes can’t produce enough aqueous fluid. Common reasons for this include:

• Aging (classic culprit)
• Medical conditions like Sjogren’s syndrome, rheumatoid arthritis, lupus, or thyroid issues
• Vitamin A deficiency
• Medications such as antihistamines, antidepressants, hormone therapy, and more
• Corneal nerve damage from contact lenses or LASIK surgery (usually temporary)

When Tears Evaporate Too Fast

Even with decent tear production, tears can vanish into thin air if the oil layer isn’t doing its job. That oily film is made by meibomian glands in the eyelids, and if they’re clogged or sluggish, things dry up fast.

Here’s what can make tears disappear too quickly:

• Meibomian gland dysfunction (posterior blepharitis)
• Reduced blinking—common when staring at screens, driving, or reading
• Eyelid alignment problems like entropion (lids turn inward) or ectropion (lids turn outward)
• Eye allergies
• Preservatives in eye drops
• Environmental factors like wind, smoke, or dry air
• Low vitamin A

Final Thoughts

Dry eyes are no joke, even if they sound like a minor nuisance. Whether it’s too few tears, too many vanishing acts, or a busted tear layer, it all adds up to discomfort and blurry vision. Fortunately, once the source is identified, there are lots of ways to help those peepers feel better.