For those of us who suffer from dry eye, winter is a particularly irritating season, especially if you live in the northern half of the country. Dry eye is not only a disease, it is also a condition that can be exacerbated by a variety of environmental factors, many of which are present during the winter months. Hot air vents, windy streets, dust, pet dander and fireplaces can turn into a dry-eye patient's worst nightmare. In an ideal world, we could send all of these patients to the Amazon jungle to treat their dry eye, but since that's not possible, we must instead educate them on how to be more aware of their condition.
In this month's column, we'll discuss the importance of "situational awareness" for dry-eye patients, and how they can use this skill to alleviate their symptoms.
The State of Dry Eye
Dry eye remains a widespread yet under- diagnosed condition. It affects up to 20 percent of the population aged 45 and older.1 The signs and symptoms of dry eye invariably result from a breakdown of the tear film involving one or more of its component layers (aqueous, lipid or mucin) and subsequent damage to the epithelial surface.
|Though dry eye can be caused by lacrimal or meibomian gland dysfunction, it can also be caused by environmental stresses.|
Causative factors for dry eye include lacrimal or meibomian gland dysfunction, menopausal changes, aging, vitamin-A deficiency, post-surgical conditions and systemic diseases such as Sjögren's syndrome, lupus and rheumatoid arthritis. Dry-eye conditions can also be caused by environmental stresses, dehydration, prolonged visual tasking, fatigue and systemic medications with drying effects such as antihistamines.
Regardless of the etiology of a patient's dry-eye disease, various environmental factors can greatly influence signs and symptoms. This is especially true in the northeastern United States during the winter months when the air is drier and humidity is decreased both outdoors and indoors. Outside, the cold weather and wind can significantly aggravate dry eye. Inside stresses include hot air vents (in homes, offices, stores and cars), lingering fumes, mites, pet dander, fireplaces and wood stoves. Both clinicians and patients should be aware of this phenomenon of seasonal dryness and understand how it affects dry eye so that the condition can be managed appropriately.
Patients with dry eye may also have a decrease in the amount of reflex tearing or a delay in tearing after exposure to an irritant. One study investigated the time to natural compensation in normal and dry-eye subjects using the Controlled Adverse Environment (CAE) model.2 This model standardizes environmental conditions including humidity, temperature, airflow, and visual tasking in order to accurately reproduce signs and symptoms of dry eye. Time to natural compensation was defined as the point at which there was a temporary improvement in ocular discomfort scores during exposure to the CAE.
|Patients should be aware of sources of hot, dry air, such as car vents, and adjust them properly.|
Normal subjects took an average of 10 minutes to naturally compensate, while subjects with mild to moderate dry eye took about 20 minutes, and severe dry-eye subjects, on average, did not exhibit any natural compensation. Thus, the dryer the ocular surface, the worse a patient feels, and the longer it bothers him, which underscores the importance of situational awareness. If patients are watchful of the conditions that exacerbate dry eye, they can learn to avoid certain situations and modify their behaviors to minimize their signs and symptoms. Encouraging a patient to exercise a high degree of vigilance is a critical component of dry-eye management.
decongestants and pain relievers)
Dry-eye patients must realize that their surrounding environment can greatly impact their disease. In winter months, they can try to avoid going outside when it is windy or wear protective glasses. They can avoid going near air vents, fireplaces or wood stoves while indoors. It's also a good idea to use portable ultrasonic humidifiers and to keep hydrated. Even being aware of blinking more frequently when performing more demanding visual tasks such as reading or using a computer can make a big difference. Infrequent blinking causes the tear film to break up more quickly, leaving the ocular surface unprotected and thus more susceptible to the signs and symptoms of dry eye. Taking breaks from visual tasking every 20 minutes may help to maintain a more contiguous tear film.
The incidence of individuals coming down with colds in the winter months is also increased compared to other times of the year, which means that more people will be taking decongestants and antihistamines, both of which can cause ocular drying. Certain systemic antihistamines, such as Claritin (loratadine, Schering-Plough) and Zyrtec (cetirizine, Pfizer), have been shown to decrease tear-film breakup time and increase ocular discomfort.3 Therefore, avoiding such medications may help prevent further damage to the ocular surface of dry-eye patients.
In addition to the significance of situational and seasonal awareness, it's important to recognize that the majority of dry-eye patients benefit from using tear substitutes to manage their dry eye. Although these products offer only transient relief that isn't necessarily optimal, they do offer protection, and most importantly, they make people feel better.
No one is forcing people to buy millions of tear substitutes every winter, but they keep flying off the shelves. Last winter approximately 7.5 million bottles/boxes of dry-eye products were sold and the numbers keep increasing. For example, in the past year, the number of bottles of the artificial tear substitute Systane (Alcon) increased 65 percent and sales of Refresh Tears (Allergan) remained at a steady million bottles.4
|Data from a 30-year period in Boston. Heating and cooling degree days are determined by temperatures above or below 65 F, serving as an indication of how much artificial cooling or heating (both of which exacerbate dry eye) is likely to be used to adjust the temperature. It is evident that, in the Northeast, heating degree days far outnumber cooling degree days.|
Source: National Environmental Satellite, Data and Information Service
Dry-eye patients need an increased tear-film barrier of protection to combat environmental stresses. Generally, artificial tears can provide this protection as well as wash away damaging mediators or allergens that may be present. In the winter months, patients may need to apply their drops more often, particularly in situations of heightened dryness. Increased awareness of exacerbating conditions will dictate how often patients need to use their drops. The use of artificial tears can allow dry-eye sufferers to recover more quickly from environmental challenge.
A recent four-week, double-blind, CAE study (n=222) comparing the secretagogue diquafosol tetrasodium (Inspire) to placebo in mild to moderate dry-eye patients tested the efficacy of the agent, but also showed the effect of environment on dry eye. (Kellerman DJ, et al. IOVS 2004;45: ARVO E-Abstract 3892)
In the study, eligible patients entered a one-week placebo run-in period and were evaluated pre- and post-CAE exposure. The researchers then randomized the patients into the treatment or placebo group and evaluated them again pre- and post-CAE exposure at four weeks.
Pre-CAE, in the placebo group, the mean corneal and conjunctival staining became worse over time, which was not the case for the treatment group. The majority of patients in this study were seen in the winter months in the northeastern United States, demonstrating that patients in the placebo group became worse because of diminished protection to the ocular surface during this time of year.
The protection provided by tear substitutes demonstrates the prophylactic effect of these products, which is particularly valuable in the winter. It shouldn't be surprising that tear substitutes can alleviate dry eye; we know that there are better options than saline solution.
Historically, the Egyptians used egg albumin to protect the ocular surface. Today, prescription products are on the way that show clinical reduction of dry-eye signs and symptoms in addition to increasing patient comfort.
Although we may still have a lot to learn about the various manifestations of dry eye, we can make use of what is available to us for treating this multifaceted condition and helping patients protect their eyes year round.
Dr. Abelson, an associate clinical professor of ophthalmology at Harvard Medical School and senior clinical scientist at Schepens Eye Research Institute, consults in ophthalmic pharmaceuticals. Mr. Ousler is director of the dry-eye department and Ms. Plumer is manager of medical communications at Ophthalmic Research Associates in North Andover.
1. Brewitt H, Sistani F. Dry eye disease: The scale of the problem. Surv Ophthalmol 2001;45:199-201.
2. Ousler GW, Abelson MB, Nally LA, et al. Evaluation of the time to "natural compensation" in normal and dry eye subject populations during exposure to a controlled adverse environment. In: Sullivan D, ed. Lacrimal Gland, Tear Film, and Dry Eye Syndromes 3. New York: Kluwer Academic/Plenum Publishers, 2002:1057-1063.
3. Ousler GW, Wilcox K, Gupta G, Abelson MB. An evaluation of the ocular drying effects of 2 systemic antihistamines: loratadine and cetirizine hydrochloride. Ann Allergy Asthma Immunol 2004;93:460-64.
4. Data generated by ACNielsen Market Research.