Dry Eye Symptoms: Causes and Treatments
As discussed in the Introduction article, there are three main areas that contribute to dry eye symptoms:
- Inadequate tear production
- Tears that evaporate too quickly from the ocular surfaces
- Imbalance between the three main components of normal tears
Inadequate Tear Production
A tear film that isn’t adequate to cover the surface of the eye completely on each blink can cause discomfort and leaves the eyes open to possible secondary infection. The source of this problem can be an underlying inflammation of the tissues of the eye, medications that are known as anti-cholinergics, and the effects of aging.
Inflammation of the ocular surface tissues often contributes to dry eye symptoms; systemic conditions such as lupus or acne rosacea or other inflammatory conditions may be at increased risk for this type of dry eye. Inflammation causes the immune system to decrease the signals that cause tears to form, creating a shortage in the eye.
Eyedrops containing cyclosporine, available by prescription under the trade name Restasis, are useful in treating inflammatory dry eye.
Topical cyclosporine reduces inflammation and is effective in about half of patients with this type of dry eye. It is the only treatment for dry eye symptoms that is NOT an eye lubricant, but an anti-inflammatory drug.
Once cyclosporine drops are started, the eye should begin to make more of its own tears, relieving symptoms, but patients should be aware that relief will not be instantaneous but can take three to six months to significantly increase tear flow. Daily use is important, however; once full effectiveness has been reached, some patients may be able to maintain the effects with a reduced dosage. Others will need to continue use of the medication at full dosage indefinitely.
In the meantime, most eyecare practitioners will ask patients to begin using ocular lubricants on a regular basis for an immediate increase in comfort. If lubricant eye drops several times a day are necessary, unpreserved, single-dose formulations may be recommended because the preservatives in larger bottles may cause a reaction if used four to six times a day.
Another method of reducing inflammation is a steroidal eye drop called Lotemax, which is also prescribed for patients just beginning treatment with cyclosporine to give immediate relief while waiting for the cyclosporine to become effective. Some steroidal drops can cause an increase in the pressure inside the eye, but this particular one is less likely to do so.
Medications with anti-colinergic side effects are relatively common and may be used to treat allergies, gastrointestinal disorders, asthma, hypertension, chronic pain and other conditions. Anticholinergic side effects cause blurred vision and dry eyes, as well as dry mouth drowsiness, sedation and decreased sweating as well as others; if you suffer from dry eyes because you take an anti-cholinergic medication, talk to your doctor about the possibility of using different medications, but do not stop taking any medication without checking with your doctor first.
If there is an adequate supply of tears being produced, but they are leaving the eye too quickly by evaporation, one way to treat this is to partially block the drainage canals so they stay in the eye longer. Blocking the drainage canals, called lacrimal punctae, is accomplished with the use of punctal plugs.
The lacrimal punctae are found in the inner corner of the each eye, one in the upper lid and one in the lower. Those in the lower lids form the major part of the drainage system from the eyes; at first, the eyecare practitioner may want to place temporary plugs in the lower canals which are made from collage and will dissolve over a few days. When the plugs are first inserted, the patient will usually notice decreased dry eye symptoms, allowing both patient and doctor to find out if they will work as expected. Once the initial pair of plugs has dissolved, plugs made from biologically inert silicone can be placed. These are permanent in the sense that they don’t dissolve, but most types of plugs are easily removable if it becomes necessary later.
If some relief from dryness is obtained from plugging the lower punctae, it is possible to place plugs in the upper punctae as well. For most patients, however, plugs in the lower punctae are adequate to solve their discomfort.
Punctal plugs are very effective for some patients, but should not be used when there is eyelid infection or inflammation; the makers of Restasis advise eyecare practitioners not to prescribe it for patients using punctal plugs.
Imbalance in Tear Components
If the dry eye symptoms are due to an imbalance in the components of the tears, such as too much mucin being secreted, treatment will depend on managing the imbalance itself.
Two of the three major components of the tears are produced by glands found in the upper and lower lids called meibomian glands. Their openings are just behind the line of the eyelashes, where they secrete either lipids which act to reduce evaporation, or mucin, which allows the tears to spread smoothly over the surface.
An imbalance of the tear layer can cause dry eye symptoms just as severe as those caused by inadequate tear production. Known as Meibomian Gland Dysfunction (MGD), this imbalance can be caused by poor lid hygiene or inflammation of the lid margins known as blepharitis. MGD is the underlying cause of many cases of dry eyes.
For an overview of dry eye, please read the article titled Dry Eye Symptoms: Introduction.
To learn more about MGD-caused dry eye symptoms, please continue with the article addressing that issue, titled Dry Eye Symptoms: Meibomian Gland Dysfunction.