Eye Diseases

Dry Eye

What is dry eye?

Some people do not produce enough tears to keep their eyes comfortable. This is known as dry eye. At 60 least million Americans suffer from some degree of dry eye, most of them over the age of 60.

What is the tear film?

The surface of the eye is covered with a thin, 3-layered tear film that has many functions, among the most important are:

• It keeps the living tissue of the eye surface moist. 
• It contains proteins which help fight infections
• It delivers oxygen and nutrients to the cornea

The three layers of the tear film:

• The outermost layer is an oily film released from the glands (Meibomian glands) on the eyelid margins. This layer retards evaporation.
• The middle layer is the watery layer containing salt, oxygen, proteins and many other components. It is mainly secreted by the lacrimal gland. This layer cleanses the eye and washes away foreign particles or irritants and helps defend against infections.
• The inner layer is the mucin layer that is made by special cells (goblet cells) lining the surface of the eye. This layer helps to spread the tear film evenly over the surface of the cornea.

What are the symptoms of dry eye?

 The usual symptoms include: 

• Stinging or burning eyes
• Scratchiness 
• Stringy mucus in or around the eyes
• Eye irritation from smoke or wind
• Excess tearing
• Difficulty in wearing contact lenses
• Photophobia (light sensitivity)
• Excess tearing from dry eye sounds illogical, but if the tears responsible for maintenance lubrication do not keep the eye wet enough, the eye becomes irritated. The lacrimal gland produces a large volume of tears which overwhelms the tear drainage system. These excess tears then overflow from the eye.

What causes dry eye?

Some people do not produce enough tears to keep their eyes comfortable. This is known as dry eye. At 60 least million Americans suffer from some degree of dry eye, most of them over the age of 60.

How is dry eye diagnosed?

(Schirmer test)

An ophthalmologist is usually able to diagnose dry eye. Often the history given by the patient makes the ophthalmic physician suspicious that dry is present. A slit lamp exam, which examines the eye surface under high magnification, is helpful. One test, called the Schirmer tear test, involves placing tiny filter paper strips under the lower eyelids to measure the rate of tear production.

How is dry eye treated?

The ophthalmologist must decide on a proper treatment plan. This depends on the underlying cause of the tear dysfunction. Often, inadequate tears is only part of the problem. Poor oily layer, malposition of the eyelids, infections, allergies, and many other conditions need to be considered.

Adding tears

• Eye drops, called artificial tears, are available without prescription. Frequency of use varies widely, from 2 to 3 times a day to several times per hour in severe cases. They come in many varieties:

•  Preservative free ampules. These are useful in avoiding the harsh preservatives found in less expensive tear preparations. Examples are: Refresh, Theratears, Bion, Akwa tears, Tears Naturale Forte, Tears Naturale II, Hypo Tears, etc.

•  Bottled tears containing mild, non-irritating preservatives. Examples are: Refresh Tears and Genteal.

•  Thicker, more viscous preparations, which include: Genteal Gel, Celluvisc, Refresh Liquigel and ophthalmic ointments. As these frequently cause blurred vision for a time, they are often best-suited for nighttime use.

• ·Eye drops containing decongestants to "get the red out" are a poor choice for prolonged use.

•  Mild steroid eye drops, available by prescription only, are sometimes used to help symptoms.

•  Investigational eye drops. The Fort Lauderdale Eye Institute has participated in an FDA study on one of the newer, not yet approved, preparations that stimulate tear production. Cyclosporin eye drops for dry eyes will probably be available soon. Hopefully, within the next 2 to 3, years there will be a number of other prescription eye drops available to help dry sufferers.

Plugging the tear ducts

If more than 3 or 4 drops daily are needed for comfort, punctual plugs frequently help. The tears drain out of the eye through small canals that run from tiny holes, called puncta, in the lids. These lead to the nose, which is why one has to blow one's nose after crying. The ophthalmologist may choose to plug up these holes, either temporarily or permanently, to help retain more of the tears produced or drops instilled. As seen in the illustration, the ophthalmologist has placed a tiny silicone plug into the tear duct. This takes a few seconds and is easily performed in the examination chair. The plugs are safe and can be easily removed if necessary.

Reducing evaporation

Tears evaporate like any other liquid. One can take steps to reduce evaporation. Humidifiers in cold weather are useful. Hair dryers must not blow into the eyes. Avoid directing air-conditioning vents toward the face. Nighttime ceiling fans are a frequent source of problems in those with dry eyes.

Avoiding irritants

Smoke is a major problem for dry eye sufferers. If you smoke or are around those who do, avoid enclosed spaces. Ammonia, bleach, hair spray, and many other irritating fumes are a special problem for those with dry eyes.

Summary

Although rarely a threat to vision, dry eye is a major cause of eye discomfort and disability. A complete exam by an ophthalmologist is required to properly assess the type and severity of the dry eye problem in order to effectively treat this distressing condition.