Dry Eyes: Various Causes, Various Treatments
One of the most frustrating and complex issues that people sometimes face is that of dry eyes. Because there are multiple causes behind the symptoms, finding the specific cause and the best treatment is not as straightforward as it may at first seem. Also, the term “dry eyes” may actually be one symptom of other conditions, such as "Sjogren’s Syndrome, Mybomian Gland Dysfunction", or, simply "Dry Eye Syndrome". Dry eyes may be one aspect of a long-term medical issue, be caused by certain medications or result from short-term disruption of the ocular tissue, such as that seen after LASIK surgery.
Dry eyes may be due to not having enough tears produced, the tears evaporating away from the eyes too quickly, or the quality of tears being produced. An imbalance between the main components of tears is often the cause. The eyecare specialist must carefully observe the tear film, test its consistency, and take a careful history of the patient’s exact symptoms, their duration and onset in order to accurately diagnose and treat this combination of symptoms successfully.
Initial causes of dry eyes can include allergies, medications, inflammatory diseases or even simply aging. Women are affected more often than men, particularly in older populations. In the past, dry eye symptoms were sometimes written off as “just one of those things” we have to put up with as we age, disregarding the fact that dry eyes are not just uncomfortable but can cause real, long-term damage to the eye. Early diagnosis and treatment help prevent this and have the added benefit of decreasing the often significant discomfort caused by it.
The most common symptoms experienced by patients with dry eyes are increasing dryness, worse either in the mornings or in the evenings, moderate to severe discomfort, excess watering, burning, stinging, redness of the eye and the tissues surrounding it, stringy or thick discharge and blurred vision.
It is rare for a patient to buy a lubricating eye drop at random out of the large array of those available which is exactly the right treatment for his or her condition; unfortunately, it’s just not that simple. A randomly chosen over-the-counter (OTC) eye drop is certainly better than nothing, but usually its effect is only short term relief, sometimes less than 20 minutes or so. To understand why OTC drops don’t always work as well as expected, it’s helpful to know more about natural and normal tears and how different underlying causes should be treated in different ways for better success.
Composition of Tears
Human tears are made up of three major layers. First, next to the ocular tissue itself is the "mucin" layer, which helps the tears stick to the eye. This layer makes up about 5% of the total tears. If there is either not enough mucin or too much mucin, or if it doesn’t have the right consistency, the tears will not stay smoothly spread over the ocular surface and cause symptoms. The tears will tend to “bead up” on the surface, in a similar way that water might bead up on the surface of a clean, waxed car.
Next is the "aqueous" layer, composed of water with a small amount of salt and other substances dissolved in it. This layer makes up about 90% of the tears. Usually, the problem here is that there is simply not enough aqueous being produced, or it is leaving the eye too quickly by evaporating or draining away too quickly.
Finally, the remaining 5% of the tears is a thin layer of "lipids", which helps prevent the tears from evaporating away too quickly. You can imagine this layer being somewhat like a thin sheet of oil on top of the water. Sometimes there may not be enough of a lipid layer to prevent evaporation, or it may be too thick or too thin to work effectively.
The main lacrimal glands are located behind the skull bones, providing most of the aqueous layer, and going into high gear when there is a foreign object in the eye, irritation from foreign substances, or emotional upset. Part of the aqueous and all of the remaining parts of the tear layer come from numerous glands located in both the upper and lower eyelids, which have openings along the lid margins, just inside the line of eyelashes. Called "Meibomian Glands", these provide both the mucin and the lipid layers of the tears. "Meibomian Gland Dysfunction (MGD)" is the underlying cause of many cases of dry eyes.
When all of these parts are functioning properly, there are adequate tears which stay on the eye without evaporating and which don’t want to “bead up” on the ocular surface. In other words, lucky patients without imbalances or improper consistencies of these have clear, comfortable vision, without dry eye symptoms.
Testing and Observation
Testing for dry eyes may include using various stains dropped into the eyes, which mix with the tears and make dry spots or areas where damage is occurring much more visible. Usually the tears are observed using an optical instrument known as a "biomicroscope" commonly called a "slit lamp". This instrument has a microscope mounted in such a way that the front of the eyes can be closely examined; it is used extensively in contact lens fitting, as well as evaluating the health of tissues such as the "conjunctiva" and "cornea", as well as the eyelids and eyelashes.
The quantity of tears may be tested using what is known as the Schirmer Tear Test, which consists of small strips of absorbent paper, folded over at one end and inserted into the lower eyelid; the length of the paper that is wet by the tears over a specific time is measured. A Schirmer test that results in less than 5 mm of wetting by the tears, for example, indicates a relatively severe lack of enough tear quantity.
There is some difference of opinion concerning "Schirmer testing", because it usually does cause a foreign body sensation in the eye if used without topical numbing drops, which can result in a false negative test. If topical anesthetic is used, some practitioners feel that the liquid of that drop added to the tears can also skew the results.
Another test for ocular dryness is called "Zone Quick", which works on the same principle, but which uses a folded thread, rather than a strip of paper. The thread changes color as it is wetted by the tears, and there seems to be much less foreign-body sensation experienced by the patient, even without anesthetic. The length of the thread that has been wetted is measured in much the same way, giving the doctor an idea of the amount of tears present.
Observation of the surface of the eye with the slit lamp by the eye doctor is done using white light and various filters, with the addition of stains which mix with the tears to make any dry spots on the surface or previously damaged tissue. The doctor can also see if the aqueous is evaporating too quickly. The patient is asked not to blink for several seconds, which may result in dry spots on the surface of the eye. This is called a "tear breakup time", and is analogous to watching water evaporate off a concrete surface on a hot day, or beading up on a newly waxed car.
In general, treatment for dry eyes will target one of three possible causes: inflammation of the ocular surface, too rapid evaporation of the tears, or an imbalance of the three components of tear composition.
Finding the specific causes of the dryness is important for long-term treatment, but it is also necessary to begin treatment right away to immediately increase comfort. There are several common-sense things patients can do to help. First, wind and drafts make symptoms worse, as do contributing factors like low humidity, such as might be found in air-conditioned buildings or outside during cold winter weather; avoid these if possible. Because we don’t blink as much when we are concentrating, a timer set every 30 minutes for relaxing the eyes and consciously blinking will be helpful.
Some patients with dry eye syndrome will experience increased comfort with an increase in the diet of Omega-3 fatty acids, usually found in some types of fish, or, more easily, in nutritional supplements.
Most patients suffering from dry eye issues will benefit from a combination of two or more strategies to relieve their symptoms.
Lubricating eye drops are usually the first treatment to be recommended by eyecare practitioners. Depending on the underlying cause, specific brands may be more useful than others, because they are not all alike; some will be more effective in treating tear insufficiency, while others can be helpful if there is an imbalance between the normal tear components.
If lubricating drops are used in treatment to supplement tear quantity, and especially if it will be used four to six times each day, it may be advisable to use unpreserved, single-use vials, to eliminate any allergic response to the preservatives in them. Even if an individual is not allergic to the preservatives, they can become toxic at higher levels in the eye.
In mild cases of dry eyes, it is appropriate to use artificial tears to help lubricate the surface tissues, but patients should ask an eyecare practitioner or pharmacist for help in choosing the right one for their particular situation. For use at night, it is sometimes helpful to choose a thicker drop that might interfere with vision during the day but isn’t an issue during sleep. During the day, slightly thicker drops such as gels may strike the right balance between lasting long enough to be useful, but not too blur-inducing for daily activities.
Inflammatory Dry Eyes
If there are indications that the tear film is inadequate, and especially if the patient suffers from inflammatory disease such as lupus or acne rosacea, a relatively new treatment is available for this specific type of tear loss, topical cyclosporine. In inflammation, the immune system causes a decrease in the signals which cause tears to form, causing a decrease in tear quantity.
Cyclosporine drops are available by prescription only. The drops work to increase tear production by reducing the inflammation. It is the only treatment for dry eye syndrome that is not an eye lubricant, but an anti-inflammatory drug; it is effective for about 15% of patients suffering from this type dry eye.
Cyclosporine eyedrops come in single-use vials in packs of 30, 60 or 180. Dosage is one drop in each eye twice a day, twelve hours apart. After three to six months of therapy, patients begin to notice increased comfort, as the eye begins to manufacture more of its own tears, relieving symptoms. It is important to continue with daily use until full effectiveness has been reached. After that, some patients may be able to retain its effectiveness with one dose per day, while others may need the full dosage, continuing indefinitely. Two factors keep some patients from attempting this strategy, however; they are cost and side effects.
Medical insurance that covers drug costs may cover cyclosporine drops. Without insurance drug coverage, a package of 60 one-use vials, a one-month supply, costs about $350.00, but there are several programs that help patients get the medication at a lower cost, utilizing coupons and reduced pricing for qualifying persons. Most individuals who have drug coverage under their medical insurance will have co-pay amounts averaging $30 to $35, but this does vary widely.
The most common side effect of topical cyclosporine is burning, followed by foreign body sensation, blurred vision, redness and watery eyes. Patients also have reported headaches and sore throat.
Patients on cyclosporine drops should use one single-use vial to instill one drop of the medication into each eye, and discard the remainder. Twelve hours later, another single-drop dose in each eye should follow, again, discarding any remaining medication. In order to use the drops exactly as the manufacturer recommends, the patient will need one 60-pack of single-use vials every 30 days.
To help alleviate the dual prohibitive-cost/burning eyes problems, some eyecare specialists have instructed their patients to use one single-dose vial in the morning, recap it and refrigerate it in the closed pack to avoid contamination, and use it again for the evening dose, discarding it afterwards. (The single-use vial can be discarded after the morning OR the evening dose, with some practitioners feeling that contamination of the vial is less likely during the night in the refrigerator.) Keeping the Restasis pack refrigerated also helps alleviate the burning on instillation factor, according to those affected by it, and also makes it easier to tell when the drop enters the eye.
Using a technique of pinching the corners of the eyes near the nose immediately after using the drops for about 30 seconds is also helpful in eliminating the sore throat and other body-wide symptoms, by keeping the drop in the eye itself and not allowing it to drain immediately into the back of the throat.
Finding the right combination of dosage and minimizing of side effects is important for successful treatment with cyclosporine. It is, as yet, the only prescription medication approved for the treatment of dry eyes in the US, but it is important to know that it will only be effective in those whose symptoms are caused by underlying inflammation. For those patients, however, results are reported to be positive for long-term relief. Many eyecare practitioners specializing in dry eye disease do feel that most cases of dry eye do have an underlying inflammatory component as their cause, making this strategy an effective and valuable ally.
Part of the prescribing information for Restasis is to use any other eye drops such as lubricants or other anti-inflammatory medications like a topical steroid drop (see below) at least 15 minutes before the cyclosporine, so that one drop doesn’t wash the other away before it can take effect. Cyclosporine is not recommended for use by pregnant or nursing women; the prescribing information also cautions patients with "punctual plugs" (also discussed below) not to use it, but this is probably only because studies have not been done in this population.
Another choice for dry eye treatment due to inflammation is a prescription steroidal eye drop. Steroids are often prescribed to treat inflammation and allergic responses. However, most steroidal eye drops can cause unwanted side effects such as increased pressure within the eye, one of the signs of "glaucoma. Some steroid eye drops are less likely to cause this particular response and is especially useful for patients who are starting out on cyclosporine, to give immediate relief instead of waiting three months before most patients notice relief using that alone.
Evaporative Dry Eyes
In patients suffering from a lack of aqueous from other factors than inflammation, such as tears that are inadequate or that are prone to evaporate too quickly, an effective treatment may be to plug the ducts that drain the tears out of the eye and into the nasal cavity.
Tears drain rather efficiently into the nose via the "puncta", four tiny tubes leading from the inside corners of the upper and lower eyelids into the upper nasal passage. (The technique of pinching the inner corners of the eyes to keep eye drops in place longer is actually just to close off these drainage ducts temporarily.)
"Punctal plugs", made of collagen or silicone fit snugly into the drainage canals; this treatment for moderate dry eyes is meant to keep the existing tears in the eye longer, relieving dry eye symptoms.
Inserting punctual plugs is a simple, in-office procedure, done with numbing eyedrops. Once the plugs are in place, most people are unaware of them. Eyecare practitioners usually start by placing them in the lower lids, using plugs made of collagen which dissolves over a period of three to five days; if the collagen plugs result in an immediate decrease in discomfort, they can then be replaced by others made of inert silicone, which do not dissolve but which can be removed later if necessary. (There are some punctual plugs which are not meant to be removed, and which fit completely inside the punctual drainage canal, but these are not recommended by many eyecare practitioners because in the case of ocular allergies or infections, the plugs may need to be removed.)
A relatively new therapy for dry eyes due to evaporation is the use of "phospholipid" or "liposomal" sprays or eye drops. These drops show promise and are effective in many cases when the dry eyes are due to rapid evaporation.
In patients with "rapid tear breakup" times, that is, those whose tears rapidly evaporate off the surface, leaving dry spots behind, liposomal spray seems to act as a replacement for an inadequate layer of lipids, which form the topmost layer of normal tears and keeps them from evaporating away too quickly.
This type of spray is available over the counter, without a prescription. There is also at least one liposomal replacement product available as eye drops.
A recent small study in Australia showed that liposomal spray is effective in reducing dryness symptoms in contact lens wearers, as well.
A recent study published and reported in the medical literature is the use of autologous serum 50% eye drops. The serum was obtained from a small amount of the patient’s own blood, which was then prepared at a compounding pharmacy using sterile saline solution to dilute it to 50% and sterilizing it. Results were very favorable using these drops; however, more research and testing will be needed before this strategy can become available for general use.
Tear Film Imbalance from Meibomian Gland Dysfunction
MGD may be one of the most under-diagnosed and under-treated ocular conditions, according to some experts. Poor meibomian gland function can result in disruption of the ocular surface, which not only effects vision but comfort. It can also be a factor in adverse events and complications after surgery, especially LASIK and cataract extraction, leading to less-than-perfect results, inflammation and even infection.
The Meibomian glands are located in both upper and lower lids, with their openings located just inside the line of eyelashes. These glands produce both the lipid and the mucin layers of the tears, as well as some part of the aqueous, so when they are not functioning properly, or become plugged and are unable to provide these components, symptoms follow.
In patients with MGD, treatment may combine several methods, including lid scrubs, hot packs and manual expression of the glands themselves. The first step in treating MGD is the improvement of lid hygiene, particularly if the gland openings are blocked. One of the most common culprits is eye makeup, especially eye liner that is placed inside the lash line, exactly where the meibomian gland duct openings are located.
All eye makeup must be removed completely each evening. In severe MGD, the use of eye makeup may need to be at least temporarily discontinued until gland function is restored and the tear film normalizes.
Occasionally, one or more meibomian glands may become impacted and infected, causing a localized lid swelling commonly called a sty, medically known as a "hordeolum". The gland and the surrounding tissue become inflamed and infected, usually with the common skin bacteria staphylococcus aureus. Over time, a hordeolum may become chronic, resulting in a hardened swollen area of lid tissue known as a "chalazion", which sometimes requires surgical treatment to strip the affected gland and its contents away.
Best Treatment Depends on Accurate Diagnosis of Cause
As discussed above, there are many possible causes for the discomfort and visual disturbances caused by dry eyes; it is obvious that the most effective treatment method(s) depend on a thorough evaluation of the tears and their components to determine where to begin. A quick trip to the pharmacy and a random choice of artificial tears will not usually be all that helpful.
Most eyecare practitioners can not only guide their patients to the right products, but may even have sample products they can provide without cost, which can be helpful even after determining the underlying cause; it is true that different products use different preservatives and concentrations of active ingredients so sampling two or three brands of the same type of eye drops is very helpful for many patients.
If you suffer from dry eyes, your eyecare practitioner is always the best source of advice and treatment.