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New Strategies in the Diagnosis and Management of Ocular Allergy

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New Strategies in the Diagnosis and Management of Ocular Allergy FEATURE SERIES OCULAR ALLERGY New Strategies in the Diagnosis and Management of Ocular Allergy Identifying allergens and teaching patients how to avoid or reduce their exposure can be a helpful first step. BY GREGG J. BERDY, MD cular allergy accounts for a large number of patients’ visits to ophthalmologists. Although “According to a survey ... of 200,000 the disorder may have an impact on the American households, 31.5% of the skin and periocular tissue, the conjunctiva is Omore commonly affected. Ocular allergy encompasses population has a spectrum of diseases characterized by antigen-specific ocular/nasal symptoms seven or immunoglobulin E (IgE) and T-helper type 2 lymphocyte- more times per year.” mediated hypersensitivity. Allergic disorders may have overlapping signs and symptoms, but each has its own pathognomonic characteristics that are useful in response has been well established.11,12 The identifica- determining the specific diagnosis. By understanding tion of histamine receptors (both histamine 1 and the pathophysiology of allergic conjunctivitis, physi- 2)13,14 has permitted investigators and clinicians to bet- cians can choose the appropriate therapy by which to ter understand its role in human allergic diseases. The control their patients’ allergic responses (Figure) and conjunctival epithelial surface contains both receptor accompanying symptoms and signs of disease. subtypes, with each receptor’s controlling a specific response to histamine. Stimulation of the H1 receptor PATHOPHYSIOLOGY causes ocular itching,15,16 whereas stimulation of the H2 Seasonal allergic conjunctivitis is the prototype of ocular receptor produces vasodilation of conjunctival vessels.17 allergy, and it begins as an antigen-IgE antibody interac- Histamine is only one of several mediators of inflam- tion on the surface of conjunctival mast cells.1 Exposure mation that are implicated in the etiology of allergic of airborne allergens to sensitized IgE-coated mast cells disease. is the initiating stimulus. The exogenous allergen binds two separate IgE mol- EPIDEMIOLOGY ecules, creating a dimer formation.2,3 This bridging of IgE According to a survey of the National Family molecules induces the activation of mast cell membrane- Opinion, Inc., database of 200,000 American house- associated enzymes, leading to the initiation of a bio- holds, 31.5% of the population (approximately chemical cascade that ultimately causes a release of 79.5 million Americans) has ocular/nasal symptoms granules into the extracellular space.4-10 seven or more times per year.18 The survey also The sentinel role of histamine in the acute allergic reported that approximately 14.5 million Americans 34 CATARACT & REFRACTIVE SURGERY TODAY MARCH 2012 FEATURE SERIES OCULAR ALLERGY have physician-diagnosed seasonal allergic rhinitis/conjunc- These symptoms are nonspecific for diagnosis; there- tivitis. In studies of patients with pollen allergy, ocular symp- fore, to make a differential diagnosis, the clinician must toms occur in approximately 75% of patients with rhinitis.19 examine the entire patient. SAC and PAC are often According to a nationwide random sample of accompanied by symptoms of allergic rhinitis: a runny Americans with rhinoconjunctivitis (N = 312) who and itchy nose, scratchy and itchy soft palate, and itchy completed the Rhinoconjunctivitis Quality of Life ear canal. These symptoms of rhinitis often accom- Questionnaire, the condition leads to a significant pany symptoms of allergic conjunctivitis, because the decline in the general health status of sufferers com- allergens and the pathophysiology of the diseases are pared with healthy controls (n = 96).20 Another survey similar.24 included 481 random American households containing Ocular symptoms may have a seasonal onset a person afflicted with rhinoconjunctivitis. It revealed (ie, SAC), occurring in the spring when the levels of that 19% of the respondents who were being treated by grass and tree pollen peak or in the fall when the levels a physician for ocular/nasal symptoms stopped seeing of weed pollen peak. PAC is chronically manifested and him or her because they believed that “effective treat- may be caused by an allergy to dust mites, feathers, or ments are not available.”21 animal dander. Upon examination, the patients’ eye- lids usually appear edematous and erythematous, and OCULAR ALLERGIC DISEASE the conjunctiva has mild to moderate chemosis with Patients with seasonal allergic conjunctivitis (SAC) injection of the bulbar and tarsal conjunctiva. A ropey, or perennial allergic conjunctivitis (PAC) present with mucosal discharge may be apparent. Itching is the complaints of red, itching, tearing, and burning eyes.22,23 most important symptom for a differential diagnosis. Figure. Diagram of the allergic cascade. Allergen exposure in a sensitized individual causes bridging of IgE molecules, which initiates a biochemical cascade and results in mast cell degranulation with the release of preformed mediators, including histamine, tryptase, ECF-A, NCF, and PAF. Degranulation of mast cell and eosinophil membranes release arachidonic acid, which is metabolized via the cyclooxygenase and lipoxygenase pathways to prostaglandins and leukotrienes, causing vasodilation and mucous production. These mediators of inflammation trigger allergic responses of itching, redness, and chemosis of the conjunctival tissue and attract eosinophils and neutrophils to the site. These cells, in turn, contain inflammatory mediators, which exacerbate and promulgate the response. In more chronic diseases, such as VKC and AKC, individuals have T-lymphocyte regulatory dysfunction, leading to chronic inflammation. (Reproduced with permission from Berdy GJ, Berdy SS. Ocular allergic disorders: disease entities and differential diagnoses. Current Allergy and Asthma Reports. 2009;9:297-303.) Abbreviations: AKC, atopic keratoconjunctivitis; ECF-A, eosinophil chemotactic factor of anaphylaxis; GM-CSF, granulocyte-macrophage colo- ny-stimulating factor; IgE, immunoglobulin E; IL, interleukin; LTB4, leukotriene B4; NCF, neutrophil chemotactic factor; PAF, platelet-activating factor; PGD2, prostaglandin D2; SAC, seasonal allergic conjunctivitis; TNF-alpha, tumor necrosis factor alpha; VKC, vernal keratoconjunctivitis. MARCH 2012 CATARACT & REFRACTIVE SURGERY TODAY 35 FEATURE SERIES OCULAR ALLERGY If the eye does not itch, then the problem is not ocular val redness, chemosis, and eyelid swelling.35 In results allergy. It should be noted that itching can be a sign of from two patient-reported outcome studies, signifi- dry eye disease, but that condition is not accompanied cantly more individuals reported being very satisfied by other seasonal symptoms and has a different ocular with olopatadine’s speed of relief and comfort than corneal staining pattern with vital dyes than allergic with azelastine 0.05% (Optivar; Meda Pharmaceuticals, conjunctivitis.25 Inc.).36 SAC and PAC are characterized by an antigen-specific Bepotastine besilate has been available for the IgE mast cell-mediated response.26 In a sensitized indi- past 2 years and is indicated for twice-daily dosing vidual, the allergen binds to IgE-coated mast cells in in adults and children 2 years of age and older. This the conjunctiva, causing mast cell degranulation and antihistamine-mast cell stabilizer has a high specificity a release of inflammatory mediators. Together, these for the histamine 1 receptor.37-39 In two well-controlled mediators produce itching, redness, and chemosis conjunctival allergen challenge studies, bepotastine of the conjunctiva—the so-called triple response to demonstrated rapid and sustained reductions in ocular allergen exposure. Recent studies have demonstrated itching, the primary endpoint.40,41 These decreases were the role of certain conjunctival dendritic cells (antigen- clinically and statistically significant at a majority of presenting cells) in the pathophysiology of ocular aller- time points.42 Also of interest was the observation that gy.27-30 Nonetheless, the histamine response continues the drug produced statistically and clinically significant to be an important contributor to the early phase of reductions in a prespecified secondary endpoint, the the allergic reaction, as mentioned previously. Non-Ocular Composite Symptom score, incorporating nasal congestion, rhinorrhea, ear/palate itching, and CHOICES FOR TREATMENT nasal itching.43 A variety of nonprescription and prescription thera- Alcaftadine is the newest entry onto the market for pies are available. Identifying the allergen and teaching the treatment of allergic conjunctivitis, and the drug patients how to avoid or reduce their exposure via offers multiple mechanisms of action (data on file with control of their environment can be a beneficial first Allergan, Inc.). In the agent’s pivotal FDA clinical trials, step. Application of topical artificial tears can dilute the 97% of subjects treated with alcaftadine reported mini- antigen load and prevent the allergens from interacting mal itching 3 minutes after the product’s instillation, with the mast cells in the conjunctiva. Cold compresses and 87% reported minimal itching 16 hours after instil- can be used as an adjunct to decrease itching. Allergen- lation.44 With its rapid onset of action and extended specific immunotherapy may be effective, and novel duration of itching control through 16 hours with one methods of administration are being developed to drop, alcaftadine addresses patients’ needs for effective improve safety and
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