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All eyecare websites usually have a list of dry eye causes. However, they're usually not all causes. Many of the things on the list are simply factors that make symptoms worse. And some simply act as triggers for a severe dry eye crisis when the underlying causes were there all along.
At the end of the day, it is impossible to differentiate amongst all these things. Most people with dry eye have multiple factors involved, and sorting out which ones are chickens, eggs, or coincidental factors is not easy.
So, I'm going to use a slightly different heading for my list:
Causes, symptom-worseners and triggers of dry eye
Aging
Aging is directly associated with a reduction in lipid production from the meibomian glands, resulting in evaporative dry eye.
Climate and other environmental factors
Outdoors and indoors, humidity levels, wind, and presence of irritants can contribute to dry eye symptoms:
- Hot, dry and/or windy climates
- High altitudes
- Central heating
- Air conditioning
- Cigarette smoke
- Air pollution
- OFFICE AIR. There are a ton of studies on this subject.
People who are exposed to any or all of these things are going to be much more likely to suffer from dry eye symptoms. Did the environment cause them to have dry eye? Not really - it's just that the environment puts so much stress on their tear film that if it is not very healthy, they're going to suffer from dry eye symptoms.
Contact lens wear
Dry eye is the most common complaint amongst contact lens wearers.
Contact lenses absorb the tear film, and rub against the conjunctiva in the eyelids, which may cause or exacerbate dry eye. Long-term contact lens wear may decrease epithelial nerve sensation, which would reduce the stimulus to produce more tears. There is also at least one study linking contact lens wear with meibomian gland dysfunction.
Diseases
- The following are often associated with the most severe forms of aqueous deficient dry eye:
- Sjogren's syndrome, lupus, rheumatoid arthritis, other auto-immune diseases
- Stevens-Johnson syndrome
- Graft-vs-host disease
There are many others such as Parkinsons, sarcoidosis and diabetes which are associated with dry eye.
Eye injuries and burns
Chemical burns and such can result in extremely severe dry eye but there's another and perhaps more common association: When you suffer a corneal abrasion from something hitting your eye or getting in it, this often leads to recurrent corneal erosions - which may not start until many months after you appear to have completely healed.
Refractive eye surgeries
or eyelid surgeries[/B]
- Elective surgeries such as LASIK, PRK, LASEK, epi LASIK, etc. LASIK is best known for dry eye because it severs or ablates more nerves than any other refractive surgery - but people can get severe dry eye from any of these surgeries. The course of healing can be very slow, taking up to two years or even more.
- Cataract surgery.
- Corneal transplants
Blepharoplasty or any corrective eyelid surgery
Anything that changes or disrupts the way your eyelid moves and whether it seals fully is going to affect your ocular surface health because your lids are a fundamental part of your ability to keep your corneas hydrated and healthy. Dry eye is a common side effect of blepharoplasty if the lids have been tightened too much and do not seal 100% during sleep or even don't blink fully during the day, leaving the cornea slightly exposed. This sometimes also happens to people with medically necessary eyelid surgeries.
Eyelid conditions or related anatomical features
- Lagophthalmos (incomplete eyelid closure - whether natural, surgically induced, caused by auto-immune hypothyroidism, etc)
- Droopy eyelid
- Bulging eye from Graves disease
- Nocturnal lagophthalmos - a common condition where you sleep with lids slightly open
- Bell's palsy
- Paralyzed eyelid (this sometimes happens after Botox injections or for other reasons)
Dermatological conditions of the eyelids
- Blepharitis - seborrheic, Staphylococcal, Demodicosis or other (here's a good link on the differences)
- Rosacea: Facial rosacea is commonly associated with ocular rosacea, which causes conditions such as blepharitis
- Eyelid allergies
Eye conditions including...
- Conjunctivalchalsis
- Pterygium/Pingecula
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!)
- Oral contraceptives
- etc.
Low blink rate
Blinking is a critical function in spreading tears over the eye surfaces and stimulating tear production. A chronic low blink rate is associated with dry eye symptoms.
Whenever focus on an object near at hand on a sustained basis, you are probably blinking much less frequently. Computer use, reading, and watching TV are the three activities most commonly associated with a low blink rate. Computer use is believed to reduce the blink rate from 22 per minute to 7 per minute.
Medications
A GREAT MANY medications can cause or exacerbate dry eye symptoms. If a medication you are using seems to be making your eyes worse, read up on side effects at sources like Drugs.com and discuss options with your doctor - s/he may be able to prescribe an alternative medication with a better side effect profile. Use common sense though - don't stop taking a medication without consulting your doctor!
Note that many medications don't list dry eye as a side effect but still can cause or exacerbate dry eye. If you see any other drying side effects on the list, such as dry mouth, the chances are...!
Here are some of the common culprits:
- 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
- Acne medications such as Accutaine
Radiation & chemotherapy
What about the big picture?
Suppose we set aside all the triggers and exacerbating factors and immediate causes to look at the big picture of "Why are we dry?". What makes us so susceptible to go dry? Why are we now seeing so many of our young people, even teenagers, getting a condition that used to be associated only with the elderly?
Personally, my answer would be as follows:
1) Lousy nutrition and an inflammatory diet undermining our bodies' ability to cope with all the things that can stress our tear film.
2) Medicines and surgeries: While trying to help one thing, we almost always hurt another.
3) Long term contact lens wear.
4) Office air.
Of course, there are going to be people for whom none of these are factors, but speaking epidemiologically, I think these are probably the top culprits.