Allergic diseases of the eye

Physicians in all specialties frequently encounter various forms of allergic diseases of the eye that present as red eyes in their general practice. However, the eye is rarely the only target for an immediate allergic-type response. Typically, patients have other atopic manifestations, such as rhinoconjunctivitis, rhinosinusitis, asthma, urticaria, or eczema. However, ocular signs and symptoms may be the initial and the most prominent feature of the entire allergic response that patients present to their physician. The prevalence of allergies ranges as high as 30% to 50% of the United States population. Industrialized countries report greater allergy prevalence, correlating with the original reports of vernal catarrh in Great Britain after the Industrial Revolution. Many theories abound about the increasing prevalence of allergies in the United States, such as increased industrialization, pollution, urbanization, and the hygiene theory. The combination of allergic nasal and ocular symptoms (rhinoconjunctivitis) is extremely common (double the prevalence of allergic rhinitis symptoms alone), but it is not clear whether the two are equal (ie, whether rhinitis is more common than conjunctivitis or vice versa). In studies of allergic rhinitis, allergic conjunctivitis is reported in more than 75% of patients, whereas asthma is reported in the range of 10% to 20% [1]. However, in some studies that report a high prevalence of seasonal allergic rhinitis in the United States, the ratio of ocular to nasal symptoms appears clearly to double throughout all sections of the country [2]. The eye is probably the most common site for the development of allergic inflammatory disorders, because it has no mechanical barrier to prevent impact of allergens such as pollen on its surface. Allergic inflammatory disorders are commonly found in conjunction with allergic rhinitis, which is considered the most common allergic disorder. Although the nasal and ocular symptoms more appropriately called conjunctivorhinitis may be perceived as a mere nuisance, their consequences can profoundly affect the patient's quality of life. Seasonal allergic rhinitis and conjunctivitis have been associated with headache and fatigue, impaired concentration and learning, loss of sleep, and reduced productivity [3,4]. Patients may also suffer from somnolence, functional impairment, and increased occupational risks for accidents or injuries secondary to sedating oral antihistamine therapy. In 70% of seasonal allergy patients, conjunctivitis symptoms are at least as severe as rhinitis symptoms [5].