Although dry eye is a common condition, its true prevalence is unknown because many people do not seek medical care for it. Experts estimate that 10 million Americans experience dry eye, the majority of whom are female.
Dry eye may exist as a separate clinical entity or it may be part of a larger symptom complex, such as Sjögren's syndrome. Certain symptoms can help pharmacists recognize dry eye as a problem. In one survey, the most common symptom of dry eye was photophobia, which ranged from minimal light intolerance to constant eye pain that required total occlusion of the eye for full relief. Intermittent to constant itching was the next most common symptom; patients felt a need to rub the eye to relieve discomfort. A seemingly paradoxical finding is that the third most commonly reported symptom of dry eye is tearing. In the mildest cases, tears do not spill over the lid, though the patient perceives a fullness of the conjunctival sac. In the most severe cases, patients experience tears that constantly spill over the lid. A feeling of discomfort is the next most common symptom of dry eye, ranging from an awareness of the eyes to severe ocular pain requiring analgesia. Patients also report that foreign material has entered the eye, ranging from the sensation of fine dust or powder to the feeling that a hot ember is embedded in the eye.
The wide variety of products available for dry eye is a reflection of its prevalence. Many of these products are demulcents -- ingredients that coat the surface of ocular tissues, protecting underlying cells from external stimuli and preventing them from drying out. The product's viscosity increases its retention time in the eye.
Some dry eye solutions employ cellulose derivatives (e.g., hydroxypropyl methylcellulose, carboxymethylcellulose) as demulcents.[3,4] The only adverse effect the patient will notice is a minor crusting around the lids shortly after instillation. If the patient experiences post-instillation tearing, the crusting will also extend to cover the tracks of the tears. The crusting is composed of the remainder of the cellulose after evaporation of solvent, and is easily wiped from the eyes, especially with a wet facial tissue. Products such as Celluvisc, Bion Tears, Refresh Plus and Tears Naturale Free contain cellulose derivatives and are available in single-use packages.
Other dry eye products contain polyvinyl alcohol, which does not form crusts because it has a lower viscosity than cellulose. This demulcent agent forms a film over the surface of the eye. Single-use products with polyvinyl alcohol include Hypo Tears PF and Refresh. Other effective ingredients found in combination in dry eye solutions include dextran 70 (which may cause transient stinging and temporarily blurred vision), gelatin, glycerin, polyethylene glycol, propylene glycol, and povidone.
Patients may also choose an ophthalmic emollient to treat dry eye. These consist of a bland ointment that forms an occlusive film on the ocular surface to prevent drying of the eye from evaporation. White petrolatum and mineral oil (sometimes combined with lanolin) are safe and effective for dry eye. Ophthalmic ointments are mainly used as nighttime dry eye treatments, however, since the oily film that covers the eye can cause a harmless and transient visual blurring.
US Pharmacist. 2001;26(12) © 2001 Jobson Publishing
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