A condition caused by the reduction in quality and quantity of tears. Common symptoms include pain from eye irritation; a sandy or gritty sensation; decreased tolerance to contact lenses; and sensitivity to light. In early stages, the symptoms may seem to appear and disappear, but generally worsen as the day progresses. The condition is typically treated with artificial tears and/or prescription drops or ointments. Closure of the tear drainage system (punctal occlusion) may also improve symptoms.
Dry eyes affect millions of people throughout the world. The condition is most common in women after menopause, but it can affect both sexes and all age groups, including children.
The symptoms of dry eyes are well known to sufferers — irritation, redness, sensitivity to light, and the constant sensation of foreign matter in the eye. However, these symptoms are less frequently recognized by health care professionals, who often neglect or minimize them. A clearer understanding of the nature and causes of dry eyes may enable sufferers to cope with their condition and participate in the care and treatment of their eyes.
There are many causes of dry eyes. Aging is certainly a factor; as people age, they secrete fewer tears, leading to dryness. Hormones probably play a role, as dry eyes are also more common in women than men, especially post-menopausal women. Systemic diseases, like Sjogren's syndrome, rheumatoid arthritis, lupus and Riley-Day syndrome, and diseases of the eye that affect the eyelids, the eye's surface or the cornea can also cause or aggravate dry eyes. Similarly, conditions which affect the eye's ability to close or to blink completely also dry out the surface of the eye.
Antihistamines, tranquilizers, blood pressure, heart medications, and other types of drugs can lead to dry eyes. Even the topical artificial teardrops used to treat dry eyes can actually aggravate the condition, due to the detergent-like preservatives they contain.
Some patients experience dryness after refractive surgery. There is a decrease in tear production following LASIK and Phototherapeutic Refractive Surgery that can persist 3-6 months. This can be significant enough that it requires frequent administration of artificial tear substitutes.
The tear film protects the eye by cleansing and flushing harmful chemicals and environmental contaminants from the surface. This anti-infectious film, which covers the surface of the eye, is like a three-layer sandwich.
The outer, or lipid, layer is very thin and oily. This layer, which floats on the surface of the tear film, is secreted by the meibomian glands located just behind the lashes in the lids. The outer layer prevents evaporation of the tear film; abnormalities and diseases of the eyelids, such as blepharitis, styes, and chalazia, cause increased evaporation and dry eyes.
The middle, or aqueous, layer is secreted by the lacrimal glands and accounts for most of the tear film. This layer provides the eye surface with oxygen and various nutrients. Sjogren's syndrome, a systemic disease characterized by dry eyes and dry mouth, affects the lacrimal gland leading to a decrease in aqueous tear secretion.
The inner, or mucin, layer is secreted by goblet cells normally present on the surface of the eye. This layer coats the eye's surface (epithelium) with a substance called mucin, which enables tears to "stick" to the surface of the eye. Deficiencies in mucin can cause dry eyes in patients with eye disorders caused by chemical injuries, Steven-Johnson syndrome, and ocular pemphigoid and systemic diseases caused by nutritional deficiencies.
The eyelids are also important in maintaining the tear film. Eyelids, which open and close normally, spread tears over the surface of the eye (epithelium). That does not occur in patients with abnormal lid position, poor lid closure, or an incomplete blink.
The epithelium keeps bacteria and other microorganisms, chemicals and pollutants from entering the eye. The epithelium and the tear film form the major refracting surface of the eye and are responsible for sharp, clear vision.
Damage to the surface of the eye accounts for the pain, foreign body sensation, difficulties with bright lights, decreased or blurred vision, increased risk of infection and problems with allergic or toxic reactions to topical eye drops in patients with dry eyes.
Initially, dry eyes are usually treated with topical lubricating drops (artificial tears) applied up to six times daily. Ointments are at times prescribed for nighttime use. Commercially available drops cannot be used more frequently because they contain detergent-based preservatives. Overuse of these drops can cause tears to break up rapidly, actually aggravating a dry eye condition. Artificial tears must be used to prevent irritation and other symptoms. Using the drops only after the eyes become irritated is not effective.
If discomfort continues, the next step is closing the tear drainage ducts. This is done with silicone or collagen plugs inserted in the tear ducts which can be removed if needed. At times, permanent cautery occlusion may be done.
Patients with dry eyes must take an active role in the treatment of their dry eyes. They must use the prescribed medications. They must protect their eyes from irritation. They must note when and where their symptoms are worse or better so their doctor can discover what contributes to their dry eyes.
For more information about dry eyes, please click here to visit www.dry-eye-syndrome.net