Dry Eye Science and Tear Lab
The Causes of Dry Eye

Dry eye is typically chronic and progressive, but it can also be transient or episodic. Dry eye is more frequently seen in females than males and is more common with increasing age. It is among the best examples of a multi-factorial disorder. In other words many different things can both cause or contribute to dry eye.
The number one cause of dry eye is meibomian gland dysfunction. The meibomian glands are small oil producing glands that run radially through down upper and lower lids. They are compressed by the lids with each blink and express a small amount of complex lipid that bonds with underlying tear structure to stabilize it and prevent evaporation. Recent research suggests that meibomian gland dysfunction (MGD) is responsible for or contributes to nearly 90% of all cases of dry eye.
Dry eye can be associated with systemic disorders such as rheumatoid arthritis, lupus, thyroid disease and Sjögren's syndrome, which causes inflammation and drying of mucous membranes of the eyes and mouth. Hormonal changes can also cause dry eye, which sometimes occurs during pregnancy.
Environmental Causes:
Hot, dry and/or windy climates, High altitudes, Excessive sun exposure, Central heating, Air conditioning, Hair dryers, Cigarette smoke, Air pollution, Air travel
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Medications:(prescription or over the counter . Allergy medications, esp. antihistamines, Antidepressants,(e.g. amitriptyline, diazepam), Some blood pressure medications, Parkinson's medications, Birth control pills, Diuretics, Beta blockers, Sleeping pills, Many pain medications, Certain medications which regulate heart rhythm irregularities, Decongestants

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Contact Lens Wear
Two million individuals abandon soft contact lens wear altogether each year with nearly 50% of these contact lens "dropouts" attributing dryness or discomfort as the primary reason.


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Diseases:
Parkinson's disease, Sjögren's syndrome (an auto-immune disease), Rheumatoid arthritis, Lupus, Lacrimal gland deficiency, Diabetes, Sarcoidosis, Stevens-Johnson syndrome, Rosacea: Facial rosacea is commonly associated with ocular rosacea, which causes conditions such as blepharitis
Refractive eye surgeries
Dry eye is the most common complaint or adverse event following LASIK.
Hormonal deficiencies or changes
Thyroid conditions, Hormonal changes during menopause, Decreased production of androgen, Estrogen supplementation -(there are reports both of this improving dry eye conditions and worsening them)
Low blink rate
Blinking is critical in spreading tears over the surface of the eye and stimulating tear production. A chronic low blink rate is associated with dry eye symptoms. Computer use, reading, and watching TV are the three activities most commonly associated with a low blink rate.
In addition to MGD, eye conditions associated with dry eye include allergy, trauma, infection, and chemical burns to the ocular surface. Eye surgeries like LASIK and cataract procedures and cosmetic procedures involving the eye can also lead to dry eye.

Medications can also cause dry eye. These include medications for allergy, hypertension, Parkinson’s syndrome, anxiety, depression and even birth control pills. Both systemic and topical medications can cause dry eye. Note that non-prescription medications like antihistamines can cause significant dry eye.

Dry eye can also be situational or environmental. Patients living in arid areas like Regina and Saskatchewan are particularly prone to dry eye. However dry eye is common in areas where signficant indoor-outdoor variations are common. This is true of tropical climates where people transit between hot high humidty outdoor conditions and cool and very dry air conditioned environments.  Dry eye is also typically worsened by close work especially work that reduces blink rates or interferes with full eyelid closure.