Dry Eye is a condition whereby the front surfaces of the eye (the cornea and conjunctiva) do not wet well. To complicate matters, the eye may be teary despite being diagnosed as dry. To better understand this apparent inconsistency, an explanation follows:

The cornea is the clear window at the front of the eye, which overlies the iris (the colored part of your eye). It is said to be hydrophobic, or water-resistant. An analogy may be made to the cornea being like a sheet of rubber. It does not wet well. If one were to shower a sheet of rubber with water from a garden hose and then turn off the hose, the water would bead up. There would be dry patches next to the water puddles on the rubber sheet. However, if a wetting agent was applied to the rubber sheet before it was showered, the water would be less likely to bead up. On the contrary, the water would coat the pre-treated area of the rubber mat uniformly.

The purpose of a quality tear film is to render the cornea more hydrophilic, or “water-loving”. In the absence of good corneal wetting, the eye is said to be dry. Hence the term “dry eye”.

The Tear Film

There are essentially three layers within the tear film. The inner most layer, the “mucous layer,” lubricates the cornea and renders it hydrophilic. Specialty cells within the conjunctiva produce mucous. The middle layer is the “water layer” and keeps the cornea in a moist and optically uniform state. It is produced primarily by the lacrimal gland. The outer layer is the “oil layer,” which reduces the evaporation of the tears. It is produced by glands in the eyelid, known as the Meibomian Glands. The openings of the Meibomian glands are on the edges of the eyelids.

Factors Contributing to Dry Eye

Patients often report that their eyes feel dry, burning, gritty or heavy after an extended period of time at the computer terminal. Their eyes may even tear in an attempt to restore the proper chemical balance and to properly lubricate and rewet the front surfaces of the eyes. These symptoms often relate to a poor-quality tear film.

There are several factors that contribute to dry eye. They include: 

v Environmental factors: The cornea is very sensitive to drying and to chemical imbalances from environmental factors. Around the office, these include dry air, ventilation fans, static buildup, airborne paper dust, laser and photocopy toner, building contaminants and the like.

v Reduced Blink Rate: Most individuals blink between 10-15 times per minute. Studies have shown that the blink-rate at the computer is significantly less. A reduced blink-rate at the video display terminal contributes to a poor quality tear film and temporary stress upon the cornea. This results in symptoms of dry eye.

v Increased Exposure: Normally, the reading of text on paper is done while looking downwards. This results in the eyelid covering a good deal of the front surface of the eye. This covering minimizes the evaporation of tears. On the other hand, computer users look at their reading material in straight ahead gaze. This results in a wider opening between the eyelids, and an increased surface area exposed to the effects of evaporation.

v Gender: The prevalence of dry eye is 4.8% in females, as compared to 2.2% in males.

v Age: Tear production normally decreases with age. Although dry eye can occur at any age in both men and women, post-menopausal women represent the group of individuals affected most by dry eye.

v Menopause: Hormonal changes and supplementation have been identified as contributing to dry eye. However, further research is required to ascertain the relative contributions of menopause and aging.

v Systemic Disease: Patients with dry mouth, dry eyes, and arthritis may be afflicted with a systemic disease known as Sjögren’s Syndrome. This is a diagnosis made by a medical practitioner, and is beyond the scope of this manual.

v Systemic Medications: Medications taken for menopause, birth control, high blood pressure (diuretics), stomach ailments, and allergies have been implicated in contributing to dry eye.

v Contact Lens Wear: “Office workers wearing contact lenses ... were found to be more likely to fall into the more severe category of ocular discomfort.³ Contact lens comfort is highly dependent on the lubrication of the eye. The contact lens surfaces should “skate” along the eye and eyelid surfaces with minimal resistance. If the eye is dry, the lenses dry and adhere to the upper eyelid during the blink. This “friction effect” from dry eye produces the discomfort described.

v Ocular Conditions: Localized dysfunctions of the glands which produce the tear-film components can also contribute to dry eye. The most common, blepharitis, is an inflammation of the eyelids. Blepharitis affects the Meibomian glands. The lack of an adequate oil layer contributes to a rapid evaporation of the water component of the tear film. This in turn, creates an imbalance in the tear film, and resultant dry eye discomfort.

v Cosmetics: Poorly applied eye-liner causes a reduction in the oil production of the tear film, because the makeup covers the openings of the oil-secreting Meibomian glands. This in turn contributes to a rapid evaporation of the water component of the tear film, and resultant discomfort.

Treatment of dry eye involves an understanding of the information above. The condition can be minimized by:

v increasing office humidity

v increasing workplace air quality

v increasing blink-rate

v correctly applying makeup so as not to cover the openings of the Meibomian glands on the lid margins (edges)

v assuring the absence of blepharitis

v using appropriate ocular lubricants and anti-inflammatory medications to rewet and restore and maintain the eye surface

v non-surgically blocking the drainage ducts to keep the fluid around the eye longer