Dry eye syndrome is an extremely common condition, thought to affect approximately 60 million Americans. The cause is usually unclear, but there appears to be an imbalance between tear production and tear volume drainage via the nasolacrimal ducts (NLD). The tear film is made up of a mucous layer against the eye, a middle aqueous (water) layer, and an outer lipid (oily) layer. All three components are critical to a normal tear film. If any of the three layers of the tear film are deficient, the eye may suffer symptoms of dry eye.
People with dry eye syndrome usually present with complaints of burning, stinging, redness of the eyes, and tearing. The tearing seems paradoxical at first, but is explained by the fact that an underlying dry eye may become irritated, perhaps sending a “signal” for increased tear production to “flush-out” the eye. This response is physiologically equivalent to the presence of a foreign body, such as a hair, in the eye. Tearing that becomes symptomatic usually occurs in conditions that more rapidly evaporate tears from the eye, such as being outdoors in the wind. Heat, low humidity, and the presence of smoke may compound the problem.
As mentioned, in most cases the cause of dry eye syndrome is unknown. However, certain other disease states as well as medications may be associated with dry eye. Patients with rheumatoid arthritis and those individuals who take antihistamines (for allergic symptoms) probably represent the largest groups of patients who present with a known cause for dry eye syndrome. Patients who present with dry eye and dry mouth may have a condition known as Sjogren’s syndrome. A large number of other conditions and medications may also be associated, but are beyond the scope of this site.
Dry eye syndrome can usually be diagnosed by ophthalmologists with the patients’ history alone, though the exam is confirmatory. On exam, the patient typically shows a reduced tear volume and rapid tear break-up time (the time for dry spots to occur on the cornea). Placement of fluorescein dye in the tear film allows the tear film to be better visualized. Some ophthalmologists will test tear production using specially prepared “tear-strips”.
The severity of dry eye syndrome generally dictates the course of treatment. In most cases, the patient is recommended to use artificial tears in the eye on a regular basis, perhaps 4 times a day. If the condition is to be treated with artificial tears chronically, many ophthalmologists will recommend non-preserved artificial tears. A humidifier in the home, especially next to the bed at night has been found to be particularly helpful for many patients. Due to “hard” tap water in most areas, however, distilled water is usually required. “Hard water” in many areas will create an airborne mineral dust, which may make the humidifier less effective for this intended purpose.
For those patients who fail to improve with the above treatment, or have a severe dry eye presentation, occlusion of the puncta (tear drainage openings) located in each of the four lids may be completed. This usually entails simple insertion of a punctal plug into one or more of the tear drainage duct openings. This procedure is quick, simple, and often very effective in helping to relieve dry eye symptoms, even in the most severe cases. The tiny plugs, usually made of silicone or other inert material, can be inserted with little or no discomfort and are rarely felt by the patient afterwards. In the unusual case that the patient then has too many tears, the plug can just as easily be removed. Some ophthalmologists choose to avoid plugs and elect to close the puncta (tear duct openings) with cautery. This is also simple and effective, although the puncta may spontaneously re-open many months or years later.
There continues to be significant clinical study in the field of dry eye syndrome. Two areas of research on the forefront of dry eye are the use topical androgens and cyclosporin. Androgens appear to play a complex but important role in tear production and studies are underway to determine if topical application of certain of these hormones may improve tear production and symptoms. Restasis (cyclosporin), an immunomodulating agent formerly used primarily in organ transplantation, is now available for patients with dry eye syndrome. The anti-inflammatory effect of topical Restasis may improve overall tear function and/or production. The drug is administered twice daily as an eyedrop and requires two to four weeks of therapy, plus daily maintenance, for a maximum benefit. A recently developed steroid eye drop known as loteprednol etabonate (brand names Alrex and Lotemax) offers a similar benefit but, unlike other steroid eye drop medications, has little or no potential to induce glaucoma or cataract. Alrex and Lotemax, FDA approved for seasonal allergic conjunctivitis (characterized primarily by ocular itching), may have a therapeutic benefit for dry eye syndrome when dosed one to four times a day.