Dry Eye Syndrome

Dry eye syndrome (DES), or simply dry eyes, is an eye disease caused by decreased tear production or increased tear film evaporation.

Epidemiology

Dry eye syndrome is relatively common within the United States, affecting those aged 40 or older. Aging is one of the most common causes of dry eyes, because tear production decreases with age.

Dry eye syndrome is usually due to inadequate tear production, resulting in aqueous tear deficiency (ATD) or lacrimal hyposecretion. The lacrimal gland does not produce sufficient tears to keep the entire conjunctiva and cornea covered by a complete layer. This usually occurs in people who are otherwise healthy. Increased age is associated with decreased tearing, and it is the most common type found in postmenopausal women.

Drugs such as isotretinoin, sedatives, diuretics, tricyclic antidepressants, antihypertensives, oral contraceptives, antihistamines, nasal decongestants, beta-blockers, phenothiazines, atropine,, and pain relieving opiates such as morphine can cause or worsen this condition.

In areas of the world where malnutrition is common, vitamin A deficiency is a common cause.

Symptoms

Typical symptoms include dryness, burning, and a sandy-gritty eye irritation that gets worse as the day goes on. Symptoms may also be described as itchy, scratchy, stingy or tired eyes. Other symptoms include pain, redness, a pulling sensation, and pressure behind the eye. There may be a feeling that something, such as a speck of dirt, is in the eye. The resultant damage to the eye surface increases discomfort and sensitivity to bright light. Both eyes usually are affected.

There may also be a stringy discharge from the eyes. Although it may seem strange, dry eye can cause the eyes to water. This can happen because the eyes are irritated. One may experience excessive tearing in the same way as one would if something got into the eye. These reflex tears will not necessarily make the eyes feel better. This is because they are the watery type that are produced in response to injury, irritation, or emotion. They do not have the lubricating qualities necessary to prevent dry eye.

Because blinking coats the eye with tears, symptoms are worsened by activities in which the rate of blinking is reduced due to prolonged use of the eyes. These activities include prolonged reading, computer usage, driving, or watching television. Symptoms increase in windy, dusty or smoky areas, in dry environments, high altitudes including airplanes, on days with low humidity, and in areas where an air conditioner, fan, heater, or even a hair dryer is being used. Symptoms reduce during cool, rainy, or foggy weather and in humid places, such as in the shower.

Most people who have dry eyes experience mild irritation with no long-term effects. However, if the condition is left untreated or becomes severe, it can produce complications that can cause eye damage, resulting in impaired vision or in the rare loss of vision. Having dry eyes for a while can lead to tiny abrasions on the surface of the eyes. Some severe cases result in thickening of the corneal surface, corneal erosion, punctate keratopathy, epithelial defects, corneal ulceration, corneal neovascularization, corneal scarring, corneal thinning, and even corneal perforation.

Symptom assessment is a key component of dry eye diagnosis, to the extent that many believe dry eye syndrome to be a symptom-based disease. Several questionnaires have been developed to determine a score that would allow for dry eye diagnosis, such at this one.

Abnormal tear composition

Dry eye syndrome can also be caused by abnormal tear composition resulting in rapid evaporation or premature destruction of the tears. When caused by rapid evaporation, it is termed evaporative dry eyes. In this, although the tear gland produces a sufficient amount of tears, the rate of evaporation of the tears is too rapid. There is a loss of water from the tears that results in tears that are too "salty" or hypertonic. As a result, the entire conjunctiva and cornea cannot be kept covered with a complete layer of tears during certain activities or in certain environments.

Additional causes

About half of all people who wear contact lenses complain of dry eyes. This is because soft contact lenses, which float on the tear film that covers the cornea, absorb the tears in the eyes. Dry eyes also occurs or gets worse after LASIK and other refractive surgeries. Dry eyes caused by these procedures usually resolves after several months, but those who are thinking about refractive surgery should consider this.

Abnormalities caused by blepharitis, rosacea, vitamin A deficiency, trachoma, diphtheric keratoconjunctivitis, mucocutaneous disorders and certain topical medications can cause dry eyes.

Diagnosis

Dry eyes can usually be diagnosed by the symptoms alone. Tests can determine both the quantity and the quality of the tears. A slit lamp examination can be performed to diagnose dry eyes and to document any damage to the eye.

A Schirmer's test can measure the amount of moisture bathing the eye. This test is useful for determining the severity of the condition. For this test, wetting under 5 mm of the test strip placed in the eye, with or without anesthesia, is considered diagnostic for dry eyes.

A tear breakup time (TBUT) test measures the time it takes for tears to break up in the eye.

The previous information is based on a current review of the literature and it is updated on a regular basis. We tailor our treatment plan to each individual.