Most people have experienced dry eye at some point in their lives, perhaps due to seasonal allergies, dry weather, contact lens overuse, or some other temporary cause. Those people may associate dry eye with such annoying symptoms as redness, scratchiness, or soreness. But did you know that chronic dry eye can be a result of aging or other systemic factors as well as environmental factors, and can have effects beyond simple discomfort? Chronic dry eye, also known as keratoconjunctivitis sicca (KCS) or dry eye syndrome (DES) is the most common eye disease, affecting over 5% of the population.
What is Dry Eye Syndrome?
In a healthy eye, tears are constantly being produced in the tear glands, and draining away through the tear ducts. These tears form a protective layer that cleans dust and debris from the surface of the eye, and keeps it moist. Dry eye syndrome refers to a chronic insufficiency in this tear film. This insufficiency may result from one of two factors, or a combination of the two: either the eye is not producing enough tears, or the tears are evaporating too quickly. Deficient tear production can be caused by many factors, including:
– Autoimmune diseases such as Sjogren’s Syndrome or lupus
– Aging; we produce less tears as we age and the oil glands (meibomian glands) on the edge of the eyelids atrophy and produce less lipid.
– Trauma to nerve endings in the cornea, such as that caused by contact lens overuse or corneal surgery
– Living or moving to a drier environment; Utah is the second driest state to live in. Places along the coasts, such as Houston or New Orleans, have high humidity which keeps the eyes, and everything else, moister.
Premature tear evaporation can cause dry eye even if the eye is producing enough tears. The tear film on a human eye is composed of three layers: the lipid layer (oils secreted by the meibomian glands); the aqueous layer (water and salts secreted by the lacrimal glands); and the mucous layer (proteins secreted by the goblet cells). Deficiency of lipid or mucous layers can cause the tears to evaporate too quickly, leaving the eye dry.
Note that the eye’s natural tear film is not the same as the tears produced when we feel pain or strong emotion. The tear film is made of what are called basal tears, composed of the three layers discussed above. Tears from pain or emotion are called reflex tears, and are composed primarily of water and salts. In fact, excessive tearing is a common symptom of dry eye syndrome, but because the tears produced are reflex tears, they evaporate quickly and do not actually decrease the chronic dryness.
How is Dry Eye Syndrome Diagnosed?
The initial diagnosis of dry eye syndrome is usually based in its symptoms. In addition to redness, discomfort, foreign body sensation (grittiness/sandiness), and excessive tearing, dry eye can actually impair vision, by two lines or more on an eye chart. For example, someone who normally sees 20/20, when suffering from severe dry eye, may only be able to see 20/40!
Once a patient presents with symptoms, a clinical diagnosis is usually based on one or more of the following tests:
– Slit lamp examination, in which the doctor uses a lamp and magnifying glass to see tiny abrasions on the surface of the eye
– Tear break-up time (TBUT) test, in which a dye called fluorescein is used to enable the doctor to time how long tears stay on the eye surface before evaporation
– A Schirmer’s test, in which a special paper strip is used to measure the amount of tears secreted by the eye
How is Dry Eye Syndrome Treated?
Treatment of dry eye can vary based on the severity and the cause(s). In cases of mild dryness due primarily to environmental factors, supplementation of the body’s natural tears with artificial tears is often sufficient. Sometimes heavier tear formulations, with oils and thickeners, can be helpful in cases of more serious temporary dryness. In cases where dryness is due to contact lens use or overuse, changes in contact lens material, wear schedule, or even a temporary hiatus from contact lens wear may be indicated.
In more severe cases, where dry eye is both chronic and severe, there are several options available:
– Punctal plugs placed into some or all of the eye’s tear ducts block the outflow of tears from the surface of the eye, keeping tears on the eye longer. These small plugs can be temporary or more permanent (but these can also be taken out when necessary). In extremely severe cases, tear ducts may be cauterized, closing them permanently.
– Restasis (Cyclosporine) is the first prescription eye drop available in the United States for stimulating increased tear production.
– Scleral lenses (large contact lenses covering the sclera, or “white of the eye” as well as the cornea) or moisture chamber glasses (sealed eyewear that covers the entire eye) serve to physically prevent evaporation or escape of eye moisture.
– Meibomian gland treatments such as Lipiflow (a very expensive warm compression device placed on the eyelids) or manual expression, can stimulate the production of lipids in the tear film, creating a longer lasting film.
Chronic dry eye affects millions of people, and its symptoms can range from the merely annoying to the truly debilitating. While there is no “one-shot” cure for dry eye, there are many treatments available that can mitigate its effects. Dry eye syndrome is just one more good reason to have regular eye checkups with a qualified eye doctor!