Dry eye disease is most often associated with tear deficiency or increased tear evaporation. The condition is a complex disease with many potential etiologies.
Dry eye is common in postmenopausal women, can be associated with some autoimmune diseases, and is often exacerbated by visual tasks (i.e., reading, working on the computer, watching television), climatic conditions (i.e., windy, dry arid conditions), wearing contact lenses, using medications that produce drying of the ocular surface (i.e., antihistamines, thyroid treatments), and other external conditions such as cigarette smoke. Because of the commonness of these environmental conditions, virtually everyone experiences the sensation of dry eye at one time or another.
With regard to eyedrops there are many to choose from, and these products span the entire range of viscosities (from thin to thick) suitable for the treatment of dry eye. Most patients will experience at least some relief from their dry eye symptoms with artificial tears of mild-to-moderate viscosity, while gel products are usually reserved for patients with more severe dry eye symptoms or for nighttime use.
Preservatives should also be considered when choosing an artificial tears product. The most frequently used ophthalmic preservative is benzalkonium chloride (BAK), which can itself be damaging and irritating to the ocular surface, particularly with frequent use.
Today there are three general classifications of products relative to preservatives content: BAK-preserved products, products preserved with non-BAK preservatives, and non-preserved products. Historically, BAK-preserved products have been the mainstay of preserved artificial tear products.
Alternate preservatives In the past few years, products with alternate preservatives have emerged, claiming superior safety to BAK preserved products. Some products such as GenTeal (Novartis Ophthalmics) and Refresh Tears (Allergan) contain preservative agents that are degraded upon exposure to the ocular surface, such as sodium perborate, or upon exposure to light, such as stabilized oxychloro complexes. This reduces the amount and time of ocular surface exposure to the preservative.
Another artificial tear product, Soothe (Alimera Sciences), is preserved with polyhexamethylene biguanide (PHMB), a preservative that in its use in contact lens solutions has met with some challenges in maintaining its antimicrobial efficacy.1
Preservative-free artificial tears are commonly used in patients with more severe dry eye symptoms or for patients who need to use multiple topical ophthalmic medications each day. Preservative-free artificial tears are typically available as single-use vials, and therefore are more expensive and can be less convenient to use than preserved products.
Available artificial tear products contain a wide range of demulcent and other additives that offer varying degrees of benefit to the patient with dry eye. For example, the lipid-containing product Soothe is considered a primarily palliative therapy, offering temporary alleviation of dry eye signs and symptoms.
Some artificial tears offer more substantive therapy, a step beyond simply alleviating the discomfort of dry eye. For example, another recent entry into the artificial tear market is Systane (Alcon Laboratories).