treatment plan

Treating Allergic Conjunctivitis

BY WILLIAM TOWNSEND, OD
OCTOBER 1998

In the autumn, eyecare providers deal with the second major wave of allergic conjunctivitis. Patients present seeking relief from red, itching eyes. The culprits in this and almost all other allergic eye conditions are mast cells and histamine receptors. Airborne pol

allergic eye conditions are mast cells and histamine receptors. Airborne pollens or other allergens contact the conjunctival surface where they eventually reach mast cells. Immunoglobulin E molecules specific to a given substance reside on the mast cell surface, and when an allergen bridges the gap between two of the IgE molecules, the mast cell degranulates. The contents of the mast cell, granules containing histamine and other inflammatory mediators, are spewed into the surrounding tissue.

A New Drop on the Block

The introduction of Livostin (levocabastine 0.05%) by CIBA Vision a few years ago, was heralded as a hallmark in the battle against allergic eye disease. Like other antihistamines, this drug prevents the binding of histamine at the various receptor sites. Livostin was immediately recognized as a very efficacious topical agent that could be successfully used to treat various allergy-related eye diseases, including seasonal allergic conjunctivitis. Alcon has recently introduced a new topical antihistamine drop, Emadine (emedastine difumarate 0.05%), which has been approved by the FDA for treating allergic conjunctivitis in patients as young as three years of age. While it has no effect on H2 receptors (vascular smooth muscle cells), Emadine does reduce and prevent the stimulation of H1 receptors (nerve endings and endothelial cells) which leads to chemosis and itching associated with allergic eye disease. The onset of action of Emadine is within five minutes. Reported side effects include ocular discomfort and headache.

In an international study by Berin et al., comparing emedastine to levocabastine, investigators reported that emedastine was superior to levocabastine in reducing signs and symptoms associated with hay fever conjunctivitis. This improvement was found to be progressive over a six week period. Another study reports that Emadine causes less ocular stinging and burning than Acular (ketorolac tromethamine 0.50%) by Allergan.

Treatment

Both Livostin and Emadine are good choices for basic, short-lived episodes of allergic conjunctivitis, but if the patient has a longer-lasting or more severe problem, consider other avenues of treatment. In addition to mast cell stabilizing activity, Patanol (olopatadine) manufactured by Alcon has a unique formulation that also gives it antihistaminic properties. We have found it to be an excellent choice for patients with more severe hay fever conjunctivitis. Crolom (cromolyn sodium) from Bausch & Lomb, and Alomide (lodoxamide) from Alcon attack allergy where it begins; they stabilize the mast cell surface and prevent degranulation. Unfortunately, it can take weeks for these products to reach their maximum effect.They are especially useful in more chronic cases of allergic eye disease.

Things To Remember

Because of their side effects, topical steroids should be reserved for pulse-dose therapy in severe cases. It's best to avoid using steroids in chronic conditions such as allergic conjunctivitis. When indicated, use a site-specific steroid such as Bausch & Lomb's Lotemax.

Allergy-related conditions will be with us for as long as we practice, but we are fortunate to have the medications available to treat these conditions. It's our duty to keep up with the potential benefits of new products and procedures to come.

Dr. Townsend is in private practice in Canyon, Texas, and is a consultant at the Amarillo VA Medical Center.