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Combination therapy may be necessary for optimal allergy management
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One of the most critical factors in managing allergic diseases is recognizing their site-specific nature. Allergic conjunctivitis is just that: an allergy localized to the conjunctiva.
What complicates matters is the propensity for allergic individuals to have multiple sensitized events; conjunctivitis, asthma or bronchial hyper-reactivity, rhinitis, eczema and other forms of allergic dermatitis can all occur in the same patient. Conversely, studies have demonstrated that even severe allergic diseases such as vernal keratoconjunctivitis can be the result of a singular localized sensitivity, even when the patient tests negative on systemic allergy tests (Leonardi A, Battista C, Gismondi M, et al. Antigen sensitivity evaluated by tear and serum IgE, skin tests, and conjunctival and nasal provocation tests in patients with ocular allergic disease. Eye. 1993;7:461-464). Knowing how to identify and treat these increasingly common patients with allergic conjunctivitis, either by itself or as a component of multiple allergies, should be a priority for optometrists.
Without the risk of oversimplifying, the key to success in treating ocular allergy is a comprehensive ocular and systemic medical history. The chances that these patients come to the office during an allergic episode are slim. However, by asking the right questions, the optometrist can easily identify an allergic patient and prescribe appropriate therapy, instead of leaving it to the patient to choose over-the-counter preparations not tailored to his or her individual needs.
The differential diagnosis
When a patient does come in with chronic symptoms, the optometrist needs to differentially diagnose ocular allergies from other masquerading conditions. Signs of allergic conjunctivitis may include conjunctival hyperemia with tearing, giving the eye a shiny appearance, unlike the redness that is often seen with dry eye. Conjunctival chemosis is sometimes present. Lid swelling is also sometimes present and can be a relatively long-lasting sign.
The hallmark symptom of itching is pathognomonic for allergy and may wax and wane as the degree of allergic exposure varies. Patients are usually aware of acute intense itching followed by cycles of itching thereafter.
Targeted treatment
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It is imperative that allergic conjunctivitis be initially treated topically. Systemic antihistamines have been shown to cause ocular dryness, thus having the potential to exacerbate ocular allergy due to diminished dilution and flushing of antigen and mediators (Abelson MB, Welch DL. An evaluation of onset and duration of action of Patanol (olopatadine hydrochloride ophthalmic solution 0.1%) compared to Claritin (loratadine 10 mg) tablets in acute allergic conjunctivitis in the conjunctival allergen challenge model. Acta Ophthalmol Scand. 2000;78(230):60-63; Nevius JM, Abelson MB, Welch D. The ocular drying effect of oral antihistamines (loratadine) in the normal population — an evaluation. Invest Ophthalmol Vis Sci. 1999;40(4) (Suppl):S549).
First-generation topical antihistamines (antazoline, pheniramine) formulated with alpha-adrenergic agonists such as naphazoline are available as over-the-counter products. While these enjoy a longstanding safety record, their duration of action is limited to 2 or 3 hours, yet are indicated only up to four times daily dosing (Abelson MB, Schaefer K, Wun PJ. Antihistamines and antihistamine/vasoconstrictor combinations. In: Allergic Diseases of the Eye. Abelson MB, ed. Philadelphia: WB Saunders Co.: 206-214). They are typically recommended in patients with infrequent isolated allergic episodes.
The first effective single-component anti-allergic agent was levocabastine, providing immediate relief of allergic symptoms and allowing instillation two or three times daily (Abelson MB, George MA, Schaefer K, Smith LM. Evaluation of the new ophthalmic antihistamine 0.05% levocabastine in the clinical allergen challenge model of allergic conjunctivitis. J Allergy Clin Immunol. 1994;94:458-464).
Mast-cell stabilizers available for treatment topically are Crolom (cromolyn sodium 4%, Bausch & Lomb); Alocril (nedocromil sodium ophthalmic solution 2%, Allergan, Irvine, Calif.); Alomide (lodoxamide tromethamine ophthalmic solution 0.1%, Alcon, Ft. Worth, Texas) and Alamast (pemirolast potassium ophthalmic solution 0.1%, Vistakon Pharmaceuticals, Jacksonville, Fla.). While none of these agents has proved to be a panacea for ocular allergy, all are preventive and all require a loading period before efficacy is observed.
Newer antihistamine/mast-cell stabilizing molecules are far more potent and long acting. Olopatadine has the broadest indication of this group, for the prevention of all signs and symptoms of ocular allergy, while other agents in this category are indicated for itching only (i.e., azelastine, epinastine and ketotifen). These newer anti-allergy agents do not need to be loaded and can be used throughout the entire allergy season. They also provide the convenience of twice-daily dosing.
When is multiple therapy necessary?
If the disease is limited solely to allergic conjunctivitis, the monotherapy of a dual-action ophthalmic solution mentioned above is typically all that is required to fully address the signs and symptoms. Naturally, more serious diseases such as vernal or atopic keratoconjunctivitis require multiple therapy with anti-inflammatory agents such as steroids, as well as dual-mechanism agents such as olopatadine. Other therapy choices should be sufficient on their own, respecting their duration of action.
The use of a tear substitute might also feel comfortable when used by allergy patients, as it can help to flush allergens from the eye. However, this non-specific defense is limited in its helpfulness, as compared to a comfortable, active anti-allergy drop, which not only lubricates the eye but also provides specific anti-allergy active ingredients.
If the patient has additional components to his or her allergy, such as rhinitis, again, the tactic of using local therapy to address a local problem provides an ideal solution. Topical nasal therapy is recommended with nasal steroids and/or mast-cell stabilizers.
If local therapy is not sufficient to control nasal signs and symptoms, systemic antihistamines may be used. If this is the case, it is particularly important to maintain or, if not already present, add a topical ophthalmic anti-allergy therapy to this regimen, not only for the localized benefit it confers, but to combat the drying effects of these systemic antihistamines. In addition, adding a tear substitute to the allergy patient’s topical regimen might help offset the ocular drying effects of these compounds.
One interesting side effect of topical allergy treatment occurs as a result of the interconnection of the eye to the nose via the nasolacrimal duct. While nasal medication has been shown to not affect ocular allergies, ocular medication, such as olopatadine, has been shown to alleviate some nasal symptoms, most likely through two effects: the prevention of allergic mediator release from mast cells in the eye (thus preventing these pro-allergic molecules from draining to the nose) or the movement of the actual drug molecule from eye to nose (Abelson MB, Turner D. A randomized, double-masked, parallel-group comparison of olopatadine 0.1% ophthalmic solution versus placebo for controlling the signs and symptoms of seasonal allergic conjunctivitis and rhinoconjunctivitis. Clin Ther. 2003;25(3):931-947).
Asthma/bronchial hyper-reactivity should also ideally be treated topically with a new-generation inhalant-formulated steroid that allows for almost no systemic absorption, as well as a bronchodilator; often, this combination is found in one inhaler.
Allergy desensitization shots
There are times when oral or topical allergy therapy is not effective enough, and a referral to an allergist for immunotherapy is warranted. Allergy “shots,” injections or desensitization, as they are referred to, are low doses of the allergen being introduced in increasing amounts over time to stimulate production of antibodies against those offending allergens. Allergy shots are only recommended for asthma, allergic rhinitis and conjunctivitis, as this form of therapy is less effective for molds and pet dander and is not proven effective for hives or food allergies.
Inadequate improvement in symptoms or the effect of the patient’s symptoms on his or her quality of life may be reason to consider immunotherapy. Another reason to consider allergy shots is poor compliance, where a patient isn’t taking his or her medication because of forgetfulness or the inability to afford it. The success of this therapy is high, but it may take several months to years to yield the full benefit.
Use an aggressive strategy
As primary eye care providers, optometrists need to adopt an aggressive strategy toward identifying allergic patients in their practices, as it is unlikely they will be seen at the office during the midst of an acute allergic episode. When the presence of allergy is ascertained, topical treatment should be the general rule, forming the foundation of therapy, with concomitant oral anti-allergy medications added to this regimen as necessary.
The use of systemic antihistamines can be reserved for cases in which rhinitis is not controlled with local therapy in a patient with rhinoconjunctivitis. Prescriptions should be issued, even out of season, so that the patient is prepared for the first sign or symptom of ocular allergy, to ensure that he or she is being treated with the optimal compound or combination of medications.
For Your Information:
- Glenn S. Corbin, OD, is in private group practice in Wyomissing, Pa., and is a member of the Clinical Practice Committee for the Pennsylvania Optometric Association. He can be reached at Wyomissing Optometric Center Inc., 50 Berkshire Ct., Wyomissing, PA 19610; (610) 374-3134; fax: (610) 374-0484; e-mail: glenn.corbin@verizon.net. Dr. Corbin is a paid consultant for Alcon.