Dry eyes are caused by a variety of reasons that disrupt the healthy tear film. Your tear film has three layers: fatty oils, aqueous fluid, and mucus.
This combination normally keeps the surface of your eyes lubricated, smooth, and clear. Problems with any of these layers can cause dry eyes.
Decreased tear production: Common causes of decreased tear production include:
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Aging
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Autoimmune disorders, allergic eye disease, thyroid disorders, or vitamin A deficiency.
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Certain medications, including antihistamines, decongestants, hormone replacement therapy, antidepressants.
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Corneal nerve desensitivity caused by contact lens use, nerve damage, or that caused by laser eye surgery.
Increased tear evaporation: Common causes of increased tear evaporation include:
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Posterior blepharitis (meibomian gland dysfunction)
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Blinking less often
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Eyelid problems, such as the lids turning outward (ectropion) and the lids turning inward (entropion)
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Wind, smoke, or dry air
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Vitamin A deficiency