DRY EYES AND THEIR TREATMENT
Prominently aired commercials serve to increase awareness of the common but frequently overlooked disorder known as Dry Eyes and their treatment. Fortunately even when undiagnosed, this nuisance complaint almost never leads to loss of vision.
Also known as Aqueous Tear Deficiency, Xerophthalmia, Keratoconjunctivitis Sicca or merely KCS its main feature involves inadequate tear coverage of the eye’s surface. Tears function to lubricate and nourish the front of the eye, provide oxygen and nutrients, focus light and remove both foreign particles and infectious organisms. Obviously interrupting tear’s normal activities may be met with problems.
Symptoms of the DES tend to occur with increasing frequency as we age with those over age 40 most at risk. The peak incidence occurs in senior citizens. Overall the prevalence ranges from one person in twenty to one in three with the burden falling more heavily on women than men. Even with so many people affected, only a tiny fraction recognize their condition and seek either self-care or medical consultation.
Symptoms tend to be mild-moderate in nature and may be either intermittent or persist for long periods. Both eyes are affected. Common complaints include a gritty, scratchy or burning feeling with irritation reminiscent of a particle of dust or sand in the eye. At times there may be pain, redness or a heavy feeling of the lids. There may be sensitivity to light, easy fatigue of the eyes while reading and difficulty keeping the eyes open while driving, working or watching the television. Stringy mucus may appear especially in the morning when the eyes may be mattered together.
Surprisingly some people with DES complain of excessive tearing. This apparent contradiction relates to two major forms of tears. The more complex Basal Tears provide lubrication and maintain the eye’s health. These are deficient in DES. Reflex Tears lack lubricating properties and result from emotion, irritation or injury. This distinction often confuses patients and doctors alike.
Basically DES exist when an imbalance exists between tear production and elimination via either evaporation into the atmosphere or drainage through tiny openings or puncta into the nose. Either the quality or the quantity of tear production may be at fault. Increasingly it seems DES represents abnormalities of the oily secretions from the Meibomian gland coupled with insufficient lacrimal gland watery tear production.
A wide array of factors lead to DES. As with everything else, normal aging reduces gland function. In women, estrogen plays a role with symptoms becoming more apparent during pregnancy and while taking either oral contraceptives or post-menopausal hormone replacement. Interestingly menopause also plays a role. Surprisingly testosterone also seems to prominently impact especially on Meibomian gland secretion of oily material. As a consequence men receiving androgen depleting therapy for prostate cancer suffer an increased rate of DES.
Environmental factors play a major role in DES. Tears evaporate quickly in smoky, windy and dry climates. Winter exposure to indoor heating and summers in the desert increase the likelihood of symptoms. The same applies to excessive use of hair dryers or driving with air directly blowing of the face. Watching television, driving long distances, prolonged staring at a computer and reading reduce blinking and hasten evaporation of tears.
Medicines may reduce tear production. Examples include anti-histamines, decongestants, certain blood pressure reducing drugs and anti-depressants. Both too much vitamin A (Accutane, isotretinoin) and inadequate amounts lead to DES. Therapy for Parkinson’s Disease along with use of opioids for pain control, sedatives and anti-anxiety medicines also contribute.
Even topical eye drops may be at fault. Beta blockers, anti-histamines and glaucoma therapies increase the risk.
Rosacea and blepharitis commonly are associated as is surgery to the front portion of the eye. LASIK and even cataract removal may damage nerves necessary for adequate tear production. The same applies to injuries, burns, scarring or physical abnormalities or deformities of the lids.
A variety of medical problems may be central to DES. These include thyroid abnormalities, diabetes, seasonal and atopic allergy, Bell’s palsy, infections around the eye with herpes simplex or the shingles virus and HIV infection. Rheumatoid arthritis, systemic lupus erythematosus and the classic Sjogren’s syndrome consisting of dry eyes and dry mouth may be intimately connected.
Proper eye function requires an adequate supply of tears. While most people imagine tears are merely water, their actual complexity continues to amaze. Basically three layers are present: oil, water, mucin.
The outer oily layer arises from Meibomian glands lining the edges of the eyelids. Although less than one eightieth the width of a red blood cell, this layer prevents evaporation of the watery tears. Proper nervous system function, hormones [especially male and female hormones] and blood vessel flow is mandatory for secretion of all the layers.
The water layer arises from the lacrimal and accessory lacrimal glands and approximates the diameter of a blood cell. It contains not only watery material but also fatty acids, thousands of different proteins, electrolytes, anti-infective compounds and an array of growth factors. Among the more well known constituents are lysozyme, lactoferrin, lacritrin, epidermal growth factor and the immunoglobulins.
The innermost mucin layer allows frictionless opening and closing of the lids together with spreading of the tears. Manufactured from goblet cells in the mucosa lining the eye together with cells of the eye’s surface itself, some of its components disperse and intermingle with the aqueous layer.
Diagnosis of DES generally remains straight forward and intuitive and for many does not necessarily require advice from a health care practitioner. However in some instances professional input assists in differentiating DES from other conditions with overlapping manifestations such as conjunctivitis, infections, corneal abrasion, rosacea or nerve injury.
Dry Eyes and Their Treatment
Treatment begins with appropriate modification of activities. Consciously blinking more frequently and looking down rather than up at the monitor reduces the amount of eye exposed and often provides relief. Avoiding air flow directed toward the face reduces evaporation. Obviously reducing exposure to dust and sand is imperative. Wrap around sunglasses help as does avoidance of cigarette smoke. Switching prescription medicines often improve the situation.
Certainly treating rosacea with antibiotics and short courses of topical steroids for allergic reactions or inflammation may offer benefits. Warm compresses, lid massage and lid cleansers may similarly provide relief.
Artificial tears generally soothe the eyes. Typical preservative containing, easily obtainable over-the-counter preparations contain products such as carboxymethylcellulose or hydroxypropyl methylcellulose. They are marketed in multi-use, screw top containers. Less expensive than the preservative free compounds they may be used many times a day as necessary. When more than four daily applications are required, the preservatives and other additives may irritate the eye. In these instances the preservative free varieties are suggested.
Unfortunately none of these lubricants mimic the actual ingredients in natural tears. They lack the wide variety of proteins, growth factors, vitamins, disease fighting immunoglobulins and more.
Other options include reducing the natural drainage into the nose of tears through the small openings located on the most central portion of the lids. An eye doctor can block these canals either with temporary plugs or more permanent methods.
Several prescriptions drops are now available. Restasis and Xiidra while heavily advertised neither cure nor even very effectively treat DES. Restasis proudly claims that it increases tear production in 15% of users compared to 5% with a placebo. Unfortunately 17% complain of burning after applying the product and even more note pain, redness or a foreign body sensation. The more recently available Xiidra slightly improves on this. Neither eliminates the need for artificial tears; they may however reduce the number of daily applications.
Omega 3 fish oils, either topically or orally, remain popular among some believers. Whether any benefit occurs remains debatable. In rare instances autologous serum may be helpful. Several drugs available in Japan but not the United States seem beneficial. These include Diquafosol and topical hyaluronic acid.
For those severely affected, moisture retaining eyeglasses that fit like swimming goggles prevent evaporation. Similarly a special type of contact lens that rests on the white portion of the eye, the sclera, maintains a moist environment.
Recent realization of the involvement of nerves in controlling of tear production opened an entirely new approach to treatment. Hopefully it will be fruit in the near future.
And DES is not limited to humans. Several breeds of dogs seem genetically predisposed. Presentation typically involves red eyes often with yellow green discharge possibly progressing to ulceration of the cornea. Among the breeds most frequently affected are bulldogs, shih tzu, pugs, cocker spaniels and Boston terriers. Cats frequently develop DES as a consequence of conjunctival infection with the Feline Herpesvirus.