Dry Eyes
Why do We Get Dry Eyes?
Our eyes constantly produce a lubrication called tears. Tears are not only important in lubricating (like oil) the eyes to allow for smooth blinking, but also, help remove foreign debris from the eye and provide important nutriments to the eye. The tears are made up of two major components: a watery component called aqueous and sandwiched between two lubricating layers (mucin and lipid layers).
The lubricating component of the tears reduces surface tension, which eliminates beading of the tears, and causes the tears to spread on the corneas (A drop of water on glass beads, spreading of the water results in dry spots, lubrication eliminates this problem). Normally tears are reflexively produced to maintain moisture of the eyes. Currently, the blink reflex to spread the tears is mediated by subliminal pain induced by dryness via the corneal nerves to the brain. The message is to produce tears. If corneal sensation is altered by lack of oxygen reducing the ability of the nerves to respond; LASIK surgery cutting the corneal nerves; contact lenses, wind or other irritants normal tearing is decreased.
If there are not enough tears a message is sent to the brain – produce more tears. Unfortunately, these tears are very watery, instead of lubricating the eye they dry the eye. The process is similar to spending too much time swimming in the ocean, the skin becomes dry. “Watery tears”, like water on your skin causes dryness. This results a new message to produce more tears. Once again, more tears are produced which dries the eyes further. This is why tearing (wet eyes) are usually the result of dry eyes.
Lastly, current research suggests that dry eye may also be caused by auto-immunological disease. The eye produces inflammatory mediators (cytokines etc.) which cause an inflammatory reaction and decrease in lubrication. New medication such as Restasis may stop the auto-immune inappropriate inflammatory reaction. The result is repair of the lacrimal gland and the resumption of normal tearing.
Is There Anything That Makes Dry Eyes Worse?
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As we grow older we produce fewer lubricates (mucin and lipid layers of tears)
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Certain diseases like arthritis cause drying of mucous membranes, e.g., mouth and eyes
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Menopause and during pregnancy result in drying of the eyes
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Medications such as anti-histamines, anti-depressants, sleeping bills, alcohol, diuretics or beta-blockers decrease
tear production
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Contact lenses increase the evaporation of tears
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Dry, windy conditions, winter (decreased humidity), pollution decrease tear production
Dry Eye problems are common complaints amongst New Yorkers. They result in symptoms of dryness, irritation, sandy or gritty feeling, foreign body sensation, tearing, and/or itching. The symptoms increase during the winter since our apartments and homes are very dry with humidity levels less than 30%. In addition, patients are trying to wear contact lenses or staring at computer screens with a decreased blink rate.
What Can We Do About Dry Eyes?
Well if you have blepharitis or meimbomitis then we must eliminate this obstacle. Put a humidifier in your apartment and/or by your desk at work. Keep it on. Otherwise, we need to supplement your tears with artificial tears. Some brands are better than others. Patients who need to be maintained on long term use should use non-preserved artificial tears other wise less expensive artificial tears may be used. My favorite brands in order are:
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Systane Ultra
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Blink
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Genteal
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Hypotears
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BION tears or Tears Naturale
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Genteal Gel (at night or for severe dry eyes during the day)