Dry Eyes Causes
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The causes of dry eyes typically involve the eye's inability to produce an adequate amount of tears. The most common cause of dry eyes is the natural aging process. Age can contribute both to poor tear quality and to a lack of tear production, (keratoconjunctivitis sicca), as the body experiences hormonal and tissue changes. Other causes of dry eyes can include certain types of medication, eyelid problems (including blepharitis), refractive eye surgery, environmental factors, and the use of contact lenses. Dry eye can also be symptomatic of some diseases, including lupus, rheumatoid arthritis, and Sjogren's syndrome. An examination by a qualified ophthalmologist is the best way to properly diagnose and determine treatment for your dry eye disease. Read on to learn more about some of the causes of dry eye syndrome.
Poor Tear Quality
The tear film that coats and lubricates your eyes has three distinct layers. An imbalance in any one of these layers is one of the major causes of dry eyes. The innermost layer is made up of mucus that allows the tear to adhere to the cornea. The middle layer is composed of 98 percent water as well as trace amounts of salt, proteins, and additional compounds. The outer layer is an oily residue that seals the tear film and prevents evaporation. The aging process can affect this balance and contribute to the onset of dry eye disease. As we grow older, our bodies produce less oil—nearly 60 percent less at age 65 than at age 18. This reduction in oil greatly impedes the sealing of the tear film’s watery layer. As a result, the tear film evaporates more quickly leaving areas of dryness across the cornea.
Diminished Tear Production (Keratoconjunctivitis)
Aging can contribute to diminished tear production, leading to keratoconjunctivitis sicca, more commonly known as dry eye disease. Diminished tear production occurs when the lacrimal gland, or tear gland, does not produce enough tears to keep the eye covered in a healthy tear film, leaving it exposed to dry air and irritants.
Many types of medications common in both prescription and over-the-counter brands have been found to be potential causes of dry eye symptoms. These medications include:
- Sleeping pills
- Birth control pills
- Decongestants and antihistamines
- Diuretic medications often used to treat high blood pressure
- Tricyclic antidepressants
- Opiate-derivative pain relievers such as morphine
- Isotretinoin-type drugs used in the treatment of acne
Aging and Menopause
Women typically have drier skin than men and as they age they tend to experience diminished tear production (keratoconjunctivitis) and poorer tear quality. A woman going through menopause can develop dry eye disease as hormonal changes affect her body.
The average person blinks about 13 times every minute. Your eyelids help moisten and lubricate your eyes by spreading a film of tears across their surface with each blink. When problems arise that impair this complex mechanism, your eyes may not receive the moisture they need and dry eye symptoms can ensue. Structural imperfections and a condition known as blepharitis are both common causes of dry eye syndrome that affect the performance of the eyelids, thereby impacting tear production.
Blepharitis is an inflammation that occurs along the edge of the eyelids, typically affecting the area of the eyelid where the eyelashes grow. Blepharitis commonly occurs when glands at the base of the eyelashes fail to produce enough oil. This results in increased bacteria growth that can inflame and irritate the eyelid. Blepharitis can produce a burning sensation in the eyes, swollen eyelids, formation of crusty material in the eyelashes, and red, watery eyes. The latter symptom represents another form of tear production known as a reflex response. Tears are formed in response to an outside stimulus, but they provide no relief from dry eyes.
Structural Eyelid Problems
Certain structural problems involving your eyelids can prevent the eyes from being properly coated by the protective tear film.
Ectropion is a term used to describe the sagging of the lower eyelids and eyelashes. As a result of this condition, your eyelids are not able to close entirely or be properly coated by the tear film when you blink. Also, your eye remains exposed to the air, which can quickly evaporate what little tear film has adhered to your eyes, resulting in drying and irritation.
Entropion describes an eyelid that has turned inward toward the eye. This can result in your eyelid and eyelashes rubbing against the delicate membrane of your eye and dispersing the tear film. In addition, this direct contact with the eye can lead to corneal scratching as well as infection, scarring, and impaired vision.
There are several common diseases that can impair the body’s ability to produce tears. Among these are rheumatoid arthritis, lupus, rosacea, and certain types of thyroid diseases. The presentation of these diseases often occurs with dry eye as a prominent symptom.
Sjogren’s syndrome is a chronic disorder that compromises the autoimmune system. It is often identified as one of the causes of dry eyes and can also lead to dry mouth, and rheumatoid arthritis or lupus.
Refractive Eye Surgery
In most refractive eye surgeries, the corneal nerves are temporarily severed in the process of creating a corneal flap. Because the corneal nerves stimulate tear production, these surgeries can be a factor in causing diminished tear production (keratoconjunctivitis) post-procedure.
LASIK and Dry Eye
LASIK and dry eye can go hand in hand. The first step of LASIK surgery involves the creation of a corneal flap. The flap is then lifted to allow access to the corneal surface, which is later reshaped with an excimer laser. During LASIK, the nerves responsible for stimulating tear production are sometimes severed. As a result, patients may develop dry eye syndrome following their surgery. Although the dry eye symptoms generally resolve as the eye heals, some patients may experience long-term issues.
There are many environmental factors that can be identified as causes of dry eye symptoms. For instance, exposure to climates that are hot, arid, or windy can significantly affect the eye’s production of tears. In addition, high altitudes, air conditioning, and cigarette smoke can have an evaporative effect on the tear film, leaving your eyes scratchy and irritated. This same effect is often experienced on an airplane that uses recycled air. Since the air tends to become very dry when recycled, your eyes are unable to produce enough of a continuous tear film to maintain their moisture. Even reading or working on a computer can leave your eyes tired and irritated. Often, this is because you tend to blink less during these activities, thereby increasing tear evaporation.
Contact Lenses and Dry Eye Irritation
Contact lens use is one of the most common causes of dry eyes. As the lens rests on the eye, it absorbs the tear film. The eye is unable to replenish the film, and subsequently begins to dry out while the lenses are in place.
Locate an Eye Care Specialist in Your City
The causes of dry eyes are varied. Though age may be the most significant factor in causing dry eye disease, leading to diminished tear production—or keratoconjunctivitis sicca—and poor tear quality, it is not the only cause. Dry eye diseases can be symptomatic of other conditions such as blepharitis and Sjogren's syndrome. There have also been links drawn between LASIK and dry eye as well as between contact lenses and dry eye. Though many people equate dry eye disease with eye irritation and discomfort, dry eyes can lead to more significant vision problems without proper treatment. Find a qualified ophthalmologist to properly diagnose and treat your dry eye disease.