- CONDITION CENTERS
This article is brought to you by Allergan Dry Eye
Dry eye syndrome is the most common ocular complaint in the United States affecting millions of Americans each year.1
The reported prevalence of dry eye garnered from different studies varies substantially from 7.8%1 to as high as 20%. Risk factors for dry eye include:
Other possible risk factors include low androgen levels, autoimmune diseases and other disorders, medication use, genetic predisposition, and alcohol use. It has been well-documented that women are twice as likely to develop dry eye and that the prevalence increases significantly with age, most especially in postmenopausal women.1-3
The major symptoms associated with dry eye include blurred vision, ocular discharge, eye discomfort, a burning sensation, increased awareness of the eye, redness, sensitivity to light, and the feeling of grit or sand in the eye.4
An accurate diagnosis may be obtained from patient history.5 Patients with dry eye will state that the eye discomfort, such as burning or a feeling of grit, gets worse as the day progresses. Symptoms may start slowly and occur episodically over weeks to months, with the eyes becoming acutely sensitive to environmental insults (eg, low humidity).
A classification system for dry eye proposed by the National Eye Institute divides dry eye into 2 categories, of which the first is the more common:
1. Deficiency of aqueous tear production (eg, from Sj?gren's syndrome, lacrimal gland disease, lacrimal gland duct obstruction, loss of reflex tearing, LASIK surgery)
2. Increased tear evaporation (eg, from meibomian gland disorder, exposure, contact lenses, blink abnormality)6
Both categories lead to an increase in tear film osmolarity. This increased osmolarity leads to an osmotic dehydration of the surface of the eye and to the symptoms associated with dry eye.5
Generally, nonprescription artificial tear products provide sufficient relief of the symptoms of dry eye.7 Artificial tear products contain demulcents that mimic the action of mucin, protectively covering and wetting the cornea.8,9 Substituted cellulose ethers (eg, carboxymethylcellulose) are water-soluble ingredients that are associated with little if any adverse effects and show a longer duration of action than other demulcents.8
Other demulcents found in artificial tear formulations include polyvinyl alcohol and water-soluble polyols, such as glycerin and propylene and polyethylene glycol. Dextran 70 has been shown to be an effective demulcent, but it can cause stinging and blurring. Although transient, these adverse effects may influence patient adherence.7
Alternative available products are ocular emollients that produce a protective film that covers the ocular surface.10 They may contain such compounds as lanolin, mineral oil, paraffin, or petrolatum. They have been shown to cause blurred vision and are therefore recommended to be applied at bedtime.11
Many ophthalmic products contain preservatives (Table 1), such as surfactants (eg, benzalkonium chloride, benzethonium chloride), metals (iodine, mercury), chlorobutanol, ethylenediaminetetraacetic acid, methylparaben, polyquaternium-1 (Polyquad), and propylparaben.12 Newer preservatives used are sodium perborate and Purite (oxychloro complex), which have been designed so that they dissociate on contact with the eye (called disappearing preservatives). These agents have demonstrated a decreased risk of the adverse effects that are associated with other preservatives.12
The presence of a preservative increases the risk of both adverse effects on the corneal surface and the possibility of hypersensitivity reactions. These risks increase with both the duration of use and the number of drops administered per day.13 The use of preservative-free products or disappearing preservatives decreases the risk of these effects and should be considered, especially for long-term therapy or high-frequency use per day.12
Artificial Tear Products
Several pharmaceutical companies manufacture numerous tear products for the treatment of dry eye. Table 1 summarizes these products and their components by brand names. These OTC products vary mainly in their ingredients, availability of preservatives, indications, and dosage forms.
The administration of products that contain substances known as compatible solutes might provide a novel approach to the treatment of dry eyes. These compatible solutes theoretically may have osmoprotective properties, which may protect the surface cells of the eye from osmotic stress. This option would seem to be a rational therapy because dry eye is known to be associated with increased osmolarity.5
Optive, a new product from Allergan, may provide a novel, effective, and safe approach to the treatment of dry eyes. Optive, designated as a next-generation tears (NGT) product, contains 2 such solutes: LCarnitine and erythritol. NGT products are purported not to change the osmolarity of the fluid of the eye but to compensate for it.
Helping Patients Choose an Artificial Tear Product
When recommending an appropriate and optimal artificial tear product for patients consider certain factors (Table 2). As a general rule, although more costly, products that are preservative-free or contain disappearing preservatives may be more appropriate for patients with more sensitive eyes. Patients who fail with a particular product may be instructed to try another product with a different ingredient, add bedtime ointment therapy, or consult a health care provider for further evaluation.
Dr. Tafreshi is an associate professor at Midwestern University College of Pharmacy-Glendale (MWU-CPG). Dr. Fisher is a professor at MWU-CPG.
For a list of references, send a stamped, self-addressed envelope to: References Department, Attn. A. Rybovic, Pharmacy Times, Ascend Media Healthcare, 103 College Road East, Princeton, NJ 08540; or send an e-mail request to: email@example.com