Dry Eye Syndrome

Disorder of the tear film that results from decreased tear production and excessive tear evaporation.

Dry Eye Syndrome is one of the most frequent patient complaints to eye doctors. Approximately 20 percent of the adult population suffers from varying degrees of dry eye problems, and an even higher proportion of elderly adults are affected.  It is a common disorder of the tear film that results from decreased tear production and excessive tear evaporation. Dry Eye Syndrome is commonly associated with a systemic inflammatory processes and like most eye diseases, it is often related to health conditions in the rest of the body. 

Methods to treat Dry Eye have been limited.

Artificial tear eyedrops, while providing temporary relief, are rapidly blinked away off the surface of the eye, through the lacrimal duct into the nose. Prescriptive eyedrops include cyclosporine, which is the same powerful chemical used to prevent rejection in bone marrow and other organ transplants. Systemic cyclosporine may increase a person's chances of getting infections.  

Several eye vitamin manufacturers have oral nutritional formulas intended to address the symptoms of dry eye.

Pathology of the three-layer tear film:

The Mucus Layer - the closest layer to the corneal epithelium. It is produced by the conjunctival goblet cells, and is absorbed by the corneal surface glycoproteins, creating a hydrophilic surface. Mucin deficiency, or mucopolysaccharide abnormalities, can lead to poor wetting or glycation of the corneal surface with subsequent desiccation and epithelial damage, even in the presence of adequate aqueous tear production.

The Aqueous Layer - the layer between the mucous and lipid layers. It is secreted by the lacrimal gland and incorporates all water-soluble components of the tear film. It also comprises 90% of the tear film's thickness. The aqueous layer provides moisture and supplies oxygen and important nutrients to the cornea.

The Lipid Layer - the most superficial layer. It is produced by the Meibomiam glands with contributions from the glands of Zeis and Moll of the eye lids. The secretion is an oily material, which is fluid at body temperature and retards evaporation of the aqueous layer and lowers surface tension, thereby allowing the tear-film to adhere to the eye's surface. Androgen receptors are located in both the lacrimal and meibomian glands. A decrease in circulating androgen hormones can result in loss of the oil layer, exacerbating the evaporative tear loss.

The Blink Reflex renews the tear film by delivering aqueous and lipid to the tear film and sweeping away debris. The normal blink interval is about 5 seconds under normal conditions. The tear film is typically stable for about 10 seconds. Tears are normally evaporated or forced out through the nasolacrimal ducts in the inner corner of the eyes on blinking.

Causes of Dry Eye Syndrome:

Many different things cause dry eye syndrome. The normal aging of tear glands, as well as extended use of contact lens, environmental pollutants, prescription drugs, refractive surgery, auto immune diseases, nutrient deficiencies and other disorders can cause disruption in the tear production and retention process.

Symptoms:

The typical symptoms of the dry eye syndrome include dryness, grittiness, irritation, difficulty reading for long periods of time, burning and even the apparent contradiction of excessive tearing or watering. In extreme cases of dry eye, patients may become unusually sensitive to light, experience severe eye pain, and start to notice diminished vision. Successful treatment may be needed to avoid permanent damage.

Blepharitis can often cause dry eye symptoms due to inflammation of the eyelid margins, which is caused by a bacterial infection (Staphylococci). This condition can compromise the quality of the tear film causing tears to evaporate more quickly. The bacteria produce waste material that can cause a mild toxic reaction leading to chronic red, irritated eyes.

Extended Contact Lens Wear can result in dry eye from corneal oxygen and nutrient deficiency. Protein build-up on contact lens can produce a breeding ground for bacterial growth and surface roughness, further contributing to inflammatory changes. Some contact lens solutions contain preservatives that can also cause chemical irritation of the corneal surface and result in dry eye symptoms.

LASIK Surgery temporarily disrupts the ocular surface/lacrimal gland unit. Also, during LASIK, roughly 60-70% of the superficial nerve fibers in the cornea are severed, which reduces sensation and affects aqueous tear production and delays wound healing. With compromised sensation, the blink rate can slow to the point that the tear film breaks up before the next blink can reconstitute. Though this condition usually clears up after a few months, it may result in mild to severe dry eye syndrome for several months after surgery.

Diseases that may be associated with dry eyes include Rheumatoid Arthritis, Sjogrens Syndrome, Diabetes, Asthma, Thyroid disease, Lupus, and possibly Glaucoma.

Age - Dry eye syndrome affects 75% of people over age 65. Tear volume decreases from age 18 as much as 60% by age 65.

Hormonal changes cause decreased tear production brought on by pregnancy, lactation, menstruation, and menopause. 

Medications that can cause dry eyes are antibiotics, blood pressure medications, antidepressants, diuretics, over-the-counter vasoconstrictors such as Visine, antihistamines, birth control pills, appetite suppressants, and ulcer medications.

Computer Use causes most people to blink less frequently (about 7 times per minute vs. a normal rate of around 22 times/minute). This leads to increased evaporation along with the fatigue and eye-strain associated with staring at a computer monitor. Any task requiring a great deal of concentration can result in decreased blink rate.

The conventional treatment for dry eyes is to treat the symptoms not the cause.

Artificial Tears: Some form of over-the-counter artificial tears is usually recommended. Although they may provide temporary relief, they merely palliate the symptoms. Worse, the preservatives can aggravate the condition, and can even kill corneal cells. Tears that promise to "get the red out" will reduce circulation in the eye, decrease production of the tear film, and worse, eventually make the eyes even drier.

Punctal Occlusion: Punctal occlusion is a procedure used to help dry eye patients by closing the tear drainage canals with silicone plugs, which keep most of the fluid from leaving the surface of the eye. This may provide long-term relief.

Restasis: The active ingredient in Restasis is cyclosporine, the same powerful chemical used to prevent rejection in bone marrow and other organ transplants.

Xiidra: Contains the drug lifitegrast, which binds to certain proteins in the body and reduces inflammation. Symptoms of dry eye disease can be caused by inflammation in the eyes. Xiidra may help improve symptoms of dry eye disease by reducing inflammation.