411 on Dry Eye Disease
June 15th, 2015 by Carolina Eye Associates
Dry eye disease is one of the most prevalent ophthalmic conditions. It may range from mild irritation while blinking to sight- threatening severe discomfort. Although it is most frequently related to insufficient activity of oil producing glands within the eyelid, it may also be a symptom of systemic disease.
Dry eye disease affects approximately 10-30 % of the population. Women are twice as likely to have the condition as men. There are an estimated 3.23 million women and 1.68 million men affected. The majority of the men are older than 50 and the women older than 40 years of age.
There are two major categories of dry eye:
1: Aqueous deficient dry eye, which is due to reduced water production, and
2: Evaporative dry eye, which is due to a lack of oil secreted into the tears by glands lining each eyelid. (Evaporative is the most prevalent form of dry eye disease). The two categories may also occur in combination. There are approximately 25 meibomian (my-bo-me-an) glands within each eyelid. The opening to these glands is at the rim of the eyelid (Fig. 1). If the secretion from these glands is not sufficient, then the tears have a diminished surface oil layer which allows the water (aqueous) layer to evaporate much too quickly. Ironically, this results in excessive tearing due to the attempt to lubricate the eye with poor quality tears. However, these tears are simply water and therefore are unable to provide adequate lubrication. It’s comparable to wetting chapped lips – water alone is not a good lubricant and does nothing to relieve the irritation.
Our tears are comprised of three layers. (Fig. 1) The tears coat the surface of the cornea (the clear front wall of the eye) as a “water sandwich.” Closest to the cornea is the mucin layer which helps the tears cling to the cornea and also makes them slick. The aqueous (water) layer is in the center and makes up approximately 98% of the thickness of the tear layer. The outermost layer is the lipid (oil) layer from the meibomian glands. The tears also contain bacteria destroying enzymes, which means they are the first line of defense against infection.
Dry eye syndrome due to lack of water (aqueous) is the result of a deficiency of the lacrimal gland (Fig. 2). Testing for aqueous deficient dry eye incorporates tests that evaluate tear volume and production over a period of time. Treatment for aqueous deficiency includes lubricating eye drops and ointments, oral supplements (omega 3s), topical cyclosporine drops, topical steroid drops, and closure of the tear drainage ducts allowing the tears to remain in contact with the eye for a longer period of time. This is achieved by inserting plugs or surgically closing the opening to the duct. “Restasis” (cyclosporine) decreases inflammation and has restorative properties for the lacrimal and mucin producing glands. There are numerous formulations of drops and supplements that your eye care physician may choose for you.
Dry eye disease, in which the quantity of tears is adequate, is the result of poor quality tears due to inactive or atrophied meibomian glands. Testing for lipid deficient (evaporative) dry eye in the past was limited to looking for blocked meibomian glands. Recent technology allows us to assess the amount of oil in the tears, as well as high definition imaging of the meibomian glands, facilitating more customized treatment. Digital meibomography allows you doctor to evaluate each gland individually to detect blockage or atrophy at a much earlier stage of the disease process. This is very important since atrophied glands do not recover.
A new treatment for this condition (Lipiflow) utilizes heat and gentle pulsation to first liquefy and then remove the solidified material within the blocked glands. This painless 12 minute treatment expresses solidified material and rejuvenates the meibomian glands allowing previously nonfunctioning glands to again produce the lipids needed to greatly increase the quality and longevity of the tears. Anti -inflammatory agents and antibiotics such as doxycycline may also be beneficial in increasing the secretions from the meibomians.
In summary, we are better equipped than ever to diagnose the deficiency causing the dry eye, and to customize a treatment plan either addressing the water deficiency by the use of lubricants, medications, nutraceuticals, and punctual (tear duct) plugs, or to enhance oil (lipid) production by re-establishing meibomian gland function with the Lipiflow system.
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