Up to half of Americans suffer from some type of allergy, and many of these people endure itchy, red eyes from ocular allergies. Although ocular allergies usually aren't vision-threatening, they're uncomfortable and often interfere with daily activities.

Searching for relief, consumers bought about 41 million bottles of over-the-counter (OTC) allergy drops during 2000, but filled only 4 million prescriptions for ocular allergy drugs, according to the Prescription Audit by ScottLevin, Inc.

Obviously, many people are self-diagnosing and self-treating their. allergy symptoms - and not receiving adequate relief.

In this article, we'll share how we recognize and treat ocular allergies so that you can relieve patients' symptoms and rule out more serious conditions. We'll focus on the more common seasonal and perennial ocular allergies, which affect as many as 95% of allergy patients.

Pinpointing masqueraders

You probably have many allergy patients in your practice, but don't be too quick to chalk up an itchy, red eye to allergy. Your differential diagnosis should take into account other conditions that redden or irritate the eye. These may include dry eye, blepharitis and rosacea, as well as other "Potential Masqueraders" as described on page 9.

Although patients with ocular allergy usually have itching, tearing or redness, their symptoms may be more subtle. That's why it's important to take the time to obtain a detailed history and perform a thorough examination.

Begin by asking patients about other allergy symptoms. Most allergy patients have allergic rhinitis and the majority of those patients also have allergic conjunctivitis, but you need to question them about it. Ask:

* Do your eyes itch or bum?

* Do your eyes tear?

* Do your eyes become red?

* How long do the symptoms last?

* When do the symptoms occur?

* What triggers the symptoms?

Environmental irritants may cause itchy, red eyes, so ask patients whether they've used new cosmetics, soaps or laundry detergent. Ask about makeup and nail polish, which may irritate the eyes. Some agents, fragrances and binders in cosmetics break down on the skin surface into a formaldehyde derivative, producing contact dermatitis, which causes more severe symptoms than seasonal or perennial allergies; these symptoms are ocular, such as redness and itching.

Follow a detailed history with a careful evaluation in a well-lit examining room. If the lights are low, you may miss critical physical signs in making the differential diagnosis.

Before using the slit lamp, perform a thorough external evaluation, carefully examining the patient's facial features. Check the skin for signs of eczema or atopic dermatitis because these patients often have allergic conjunctivitis. Also, rule out viral conjunctivitis, infectious conjunctivitis and blepharoconjunctivitis. Remember, patients with infectious causes will have matting of eyelashes and purulent discharge.

When differentiating between the types of ocular allergies, keep in mind that patients with seasonal allergic conjunctivitis don't have tissue damage. Therefore, they wouldn't be expected to have pain, severe redness or decreased vision, which would be associated in patients with atopic keratoconjunctivitis and vernal keratoconjunctivitis, two less common, more severe ocular allergic conditions.

Seasonal allergies usually cause bilateral symptoms, but occasionally may cause unilateral symptoms. For example, your patient may have touched an allergy-triggering object, such as a cat, then rubbed his eye. If the irritation occurs in only one eye, it could be an allergic reaction, but more likely there's another nonallergic cause.

Developing a treatment plan

The patient's symptoms and your diagnosis will guide you to the best treatment. All oral antihistamines - even new-generation drugs such as loratadine (Claritin), cetirizine HCl (Zyrtec) and fexofenadine HCl (Allegra) - dry the eye, worsening ocular symptoms and confounding the differential diagnosis of the red, itchy eye. Consequently, many doctors avoid oral medications.

We prefer to treat topical diseases topically, using a nasal steroid for rhinitis and prescription anti-allergy eye drops for conjunctivitis. In a study comparing the combined use of fluticasone propionate (Flonase Nasal Spray) and fexofenadine HCl with the combination of fluticasone propionate and olopatadine HCl 0.1% (Patanol), the latter group fared better in regard to ocular and nasal symptoms. As an added benefit, the olopatadine eye drop is absorbed into the nasolacrimal system, reducing rhinitis symptoms due to its antihistaminic properties. Unlike oral medications, topical drops have no systemic side effects. Additionally, your patients can safely use topical drops for extended periods, as was proven in a 19-week study by Mark Abelson, M.D., Gregg Berdy, M.D., et al., in the Journal of Ocular Pharmacology and Therapeutics, in which they found pemirolast potassium provided extended efficacy and was as safe as a placebo.

If a patient needs an oral antihistamine to relieve symptoms, we also prescribe artificial tears to offset the drying effect of the medication.

Generally, we choose from these treatment options:

* Artificial tears. Artificial tears soothe the eye and wash away allergens. They act as a diluent and form a barrier to inhibit allergen contact with the conjunctival surface and mast cells. They can be even more soothing if refrigerated, causing a vasoconstrictor effect.

As corneal specialists, we prefer preservative-- free tears because preservatives can irritate the eye, causing medicamentosa conjunctivitis, which can mimic the signs and symptoms of allergic conjunctivitis. And that's what we don't want.

* Mast cell stabilizers. Mast cell stabilizers, such as cromolyn sodium 4% (Crolom) and lodoxamide tromethamine (Alomide), prevent symptoms by stabilizing mast cells and blocking the release of inflammatory mediators, but can be safely used seasonally or perennially.

To prevent seasonal allergy symptoms, patients need to begin using the drops a week before allergy season begins. Be sure to explain the prophylactic nature of these drugs because patients may stop using them if they don't notice an effect.

Newer second-generation mast cell stabilizers, such as nedocromil sodium 2% (Alocril) and pemirolast potassium 0.1% (Alamast), work more rapidly than the first generation, providing relief of symptoms in minutes and therapeutic benefits in a few days.

* Antihistamines. Antihistamines, such as levocabastine HCl 0.05% (Livostin) and emedastine 0.1% (Emadine), competitively inhibit histamine binding to histamine HI receptors on nerve endings to relieve itching. Also, studies show that these drugs reduce redness, chemosis and tearing.

* Combination antihistamine/mast cell stabilizers. Although mast cell stabilizers can prevent allergy symptoms when used prophylactically, patients often don't see their eyecare professional until symptoms have begun. Therefore, combination antihistamine/mast cell stabilizers, such as olopatadine HCl 0.1%, azelastine HCI 0.05% (Optivar) and ketotifen fumarate 0.025% (Zaditor), have become popular options, relieving symptoms rapidly by blocking HI receptors and preventing the further development of symptoms by stabilizing mast cells.

In patients with ocular allergies, rubbing their eyes degranulates mast cells, continuing symptoms. It's important to remind patients not to rub their eyes, even though it initially makes them feel better. Incidentally, if a patient has red, itchy eyes every spring, prescribe either a mast cell stabilizer or a combination antihistamine/mast cell stabilizer several days before allergy season begins.

1 Nonsteroidal anti-inflammatory drug. Ketorolac tromethamine 0.5% (Acular) inhibits cyclooxygenase, which blocks the production of prostaglandins from arachidonic acid metabolism. Nonsteroidal anti-inflammatory drugs (NSAIDs) don't inhibit lipoxygenase and therefore don't stop production of leukotrienes. Similarly, NSAIDs don't block mast cell release of mediators or inhibit histamine.

I Steroids. Topical steroids effectively stabilize all types of white blood cells, including mast cells, but they may take 4 to 7 days to work. In addition, most steroid eye drops must be used four times a day. Furthermore, steroid eye drops may predispose patients to ocular surface infection, increased intraocular pressure and cataract formation.

Loteprednol etabonate 0.2% (Alrex) is the only ocular steroid approved by the FDA for the temporary relief of the signs and symptoms of allergic conjunctivitis.

* OTC medications. We have two groups of topical OTC ocular medications at our disposal: 1. Vasoconstrictor/astringents (tetrahydrozoline [Visine, Murine Tears])

2. Antihistamine/vasoconstrictor agents (naphazoline and pheniramine [Naphcon-A]; naphazoline and antazoline [Vasocon A]; naphazoline [Albalon-A]).

The first group reduces redness and swelling, and the second group reduces itching and redness. They are fast-acting, but last only 2 to 4 hours, so patients may need to dose more frequently, which may cause medicamentosa or a rebound effect. Increasing compliance Patients are more likely to use a drug if it's effective, provides rapid relief and doesn't cause discomfort. Because drugs such as pemirolast potassium and olopatadine are comfortable, patients will be more likely to use them.

Patients also are more likely to use drugs with less frequent dosing. When prescribing mast cell stabilizers, such as pemirolast potassium, lodoxamide tromethamine and nedocromil sodium, we've found it just as effective if you start the patient using the drug four times a day for a few days, then decrease the frequency to twice a day. Follow-up care for patients with seasonal allergic conjunctivitis is less important now than it was in the past. The new allergy drugs are so effective that we have fewer treatment failures due to soothing formulations that in many instances improve compliance. Allergy patients usually schedule follow-up appointments only if their treatment is inadequate.

Satisfied patients

Many of your patients endure ocular allergy symptoms that may interfere with their daily lives. Although allergies are a very common cause of redness and itching, it's important to take the time to make an accurate diagnosis and rule out more serious conditions. Based on this diagnosis, you can select medication that effectively eliminates your patients' symptoms so they can return to the activities they enjoy.

By Peter A. D'Arienzo, M.D., FA.C.S., and Gregg J. Berdy, M.D., F.A.C.S.

Dr. D'Arienzo is a clinical assistant professor of ophthalmology, New York Medical College, and clinical director of the department of ophthalmology, St. Vincent Catholic Medical Centers, Brooklyn and Queens Region. He's also in private practice in Manhasset, N.Y.

Dr. Berdy is a clinical instructor of ophthalmology, Washington University School of Medicine, St. Louis. He's in private practice in St. Louis, specializing in corneal and external disease.

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