Dry eyes are more than just a minor annoyance—they’re a sign that something’s not working quite right on the surface of your eyes. At Byedryeyes.com, we believe that understanding the science behind dry eye syndrome can empower you to take control of your symptoms and find lasting relief.
In this article, we’ll break down what causes dry eyes at a biological level, how the tear film works, and what can go wrong—explained clearly, without the confusing medical jargon.
What Is Dry Eye Syndrome?
Dry eye syndrome (also called dry eye disease or keratoconjunctivitis sicca) is a condition where your eyes don't produce enough quality tears to stay properly lubricated. It’s a common problem, especially as we age, and can lead to symptoms like:
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Burning or stinging
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Grittiness (like something is in your eye)
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Redness
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Blurred vision
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Eye fatigue
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Excessive tearing (yes, really!)
But why does this happen? To understand that, let’s look at how healthy eyes work.
The Tear Film: Your Eye’s Natural Defense
Your eyes are protected by a thin layer of tears called the tear film, which coats the surface of the eye (the cornea). This film is incredibly important—it keeps your vision clear, prevents infection, and nourishes your eyes with oxygen and nutrients.
The tear film has three key layers:
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Lipid (oil) layer – The outermost layer, made by the meibomian glands, prevents your tears from evaporating too quickly.
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Aqueous (water) layer – The middle layer, produced by the lacrimal glands, hydrates the eye and flushes away debris.
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Mucin (mucus) layer – The innermost layer, made by goblet cells in the conjunctiva, helps spread the tears evenly across your eye.
When one or more of these layers is disrupted, dry eye symptoms can develop.
The Two Main Causes of Dry Eye
1. Evaporative Dry Eye
This is the most common type and occurs when the lipid layer is too thin or missing. Without enough oil, tears evaporate quickly—leaving your eyes dry and irritated. The primary culprit? Meibomian Gland Dysfunction (MGD), where the tiny oil glands in your eyelids become blocked or inflamed.
2. Aqueous-Deficient Dry Eye
In this form, your eyes don’t produce enough of the aqueous (water) layer. This can happen due to aging, autoimmune diseases (like Sjögren’s syndrome), or side effects from medications like antihistamines, antidepressants, or blood pressure drugs.
Many people actually have mixed dry eye, a combination of both evaporative and aqueous-deficient types.
What Causes These Disruptions?
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Aging: Tear production naturally decreases as we get older, especially after age 50.
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Hormonal changes: Estrogen and androgen levels (especially during menopause) can affect tear glands.
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Environment: Dry climates, wind, smoke, and screen use can all reduce blinking and increase evaporation.
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Health conditions: Autoimmune diseases, diabetes, and eyelid inflammation (blepharitis) can contribute.
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Medications: Common drugs like decongestants, antihistamines, and beta blockers can reduce tear production.
Inflammation: The Silent Culprit
One of the key scientific findings in dry eye research is the role of inflammation. When your tear film breaks down, it leads to irritation and microscopic damage to the eye’s surface. This triggers an immune response, releasing inflammatory molecules that further reduce tear quality—and create a cycle of worsening dryness.
That’s why many modern dry eye treatments, like anti-inflammatory eye drops, are designed to break that cycle.
The Future of Dry Eye Treatment
Ongoing research is helping eye care professionals better understand the cellular and molecular causes of dry eye. New treatments target not just the symptoms, but the underlying biological processes, including:
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Improving meibomian gland function
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Regulating tear production
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Reducing inflammation
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Supporting nerve regeneration in the cornea
Final Thoughts
Dry eye syndrome is a complex condition with many contributing factors—but the science behind it is becoming clearer every day. Understanding the layers of the tear film, the causes of dysfunction, and the role of inflammation gives you a stronger foundation for managing your symptoms.
At Byedryeyes.com, we’re committed to educating and supporting you with trustworthy, science-backed information. Explore our resources, talk to your eye care professional, and know this: relief is possible.
Need help identifying your type of dry eye? Browse our symptom guides or take our dry eye quiz to learn more about your condition—and how to treat it effectively