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The advent of spring yields the annual pilgrimage of patients into our offices complaining of the itchy, watery eyes of allergy. As any eyecare practitioner can attest, ocular allergy is one of the most common presentations to an eyecare practice.
The advent of spring yields the annual pilgrimage of patients into our offices complaining of the itchy, watery eyes of allergy. As any eyecare practitioner can attest, ocular allergy is one of the most common presentations to an eyecare practice. The ocular conjunctiva is particularly susceptible to airborne allergens and is a very common site of allergic inflammation.1
Ocular allergy presents in conjunction with other systemic atopic manifestations, including rhinoconjunctivitis (hay fever), rhinosinusitis, asthma, urticaria (hives), and/or atopic dermatitis (eczema).1 Ocular allergy includes a spectrum of disorders with overlapping symptoms and progressing in severity; these disorders include seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC), atopic keratoconjunctivitis (AKC), and vernal keratoconjunctivitis (VKC). SAC and PAC are the most common forms of ocular allergy.
Approximately 15-20 percent of the world population is affected by some form of allergic disease. Ocular symptoms present in about 40-60 percent of allergic patients2 and contribute significantly to poor quality of life.3 Most recent estimates suggest that 15–25 percent of the U.S. population, or between 50 and 85 million Americans, suffer from ocular allergy and/or allergic conjunctivitis.4,5 Other studies have estimated the prevalence of allergic conjunctivitis to range between 15 and 40 percent of the U.S. population.6 Here in the United States, the National Health and Nutrition Examination Survey III (NHANES III) found that 40 percent of the adult population had ocular symptoms, defined as “episodes of tearing and ocular itching, with no significant differences according to age, though there was a predominance in the south vs. other regions of the country.7 The prevalence of allergic conjunctivitis is similar in Europe, Japan, and Australia, and is increasing worldwide.6
According to an analysis from 1993 to 2008, prescribing medications for allergic conditions has similarly accelerated by about 20 percent.8 This likely reflects an increasing prevalence of allergic disease in developed countries. Although the exact reason for this increase is not known, many factors are thought to play a role, including air pollution, industrialization and urbanization, climate change, and the “hygiene hypothesis,” which in essence attributes immune hypersensitivity among city dwellers to low microbial exposure during childhood.1,9
While not life threatening, the symptoms of ocular allergy as suffered by affected individuals have a significant impact on their productivity and quality of life.10 Ocular allergy symptoms can produce patient discomfort and interfere with visual tasks, including computer work and recreational activities. The quality of life of patients dealing with allergic conjunctivitis can be affected by intense itching, which produces sensation of dryness, vision fatigue and reading difficulties. Some 20 percent of allergy suffers report missing some time from work due to allergy symptoms.11 More severe forms of the ocular allergy, such as AKC12 or VKC,13 are rare yet can be sight threatening. Similar to other allergic conditions, allergic conjunctivitis may demonstrate both an early, acute phase triggered by mast cell degranulation and a late, chronic phase involving allergic inflammation.14
SAC and PAC have seen a worldwide trend of increased prevalence over the past few decades.6 For example, increases in SAC and PAC in children have been well documented by the International Study of Asthma and Allergies in Childhood (ISAAC).15 Earlier studies suggest a difference between children from developed countries and those from more rural countries: while the overall health of children from underdeveloped countries may be worse, their risk of developing allergic disease was substantially lower than that seen in Europe, North America, or Japan.16 Nations undergoing substantial economic growth report spikes in the prevalence of allergic conjunctivitis and symptoms associated with rhinitis or allergic conjunctivitis.16
Another factor in the rise in allergic disease prevalence receiving considerable attention in recent literature is the role of air pollution as an exacerbating factor in allergic signs and symptoms.17 About 89 percent of the world’s population lives in areas where the levels of airborne particulate matter exceed the World Health Organization’s (WHO) guidelines for air quality.18 There is also evidence that suggests some allergic resistance is passed passively from mother to child. Children born by Caesarean section19 and those who were fed milk other than breast milk during the first 4 months of life20 have an increased risk of developing allergies.
Allergic conjunctivitis is caused by an allergen-induced inflammatory response in which allergens interact with IgE bound to sensitized mast cells, producing the clinical ocular allergic presentation. Environmental allergens trigger both SAC and PAC.21 Symptoms of allergic conjunctivitis may fluctuate throughout the year, but they worsen during times of highest allergen exposure and in weather that is warm, windy, and dry. The hallmark signs and symptoms of both SAC and PAC are itching and redness,22 but the hallmark symptom of allergic conjunctivitis is itching.
A diagnosis of allergic conjunctivitis should be questioned if a patient isn’t complaining with an itch.23 Itching may be particularly aggravating in the nasal aspect of the eye and may range from mild to severe. Other symptoms include burning, stinging, photophobia, tearing, watery or mucoid discharge, chemosis, or dry eye.22 The discharge may contain a small amount of mucus, rendering it stringy or ropy, which could occasionally lead to a misdiagnosis of bacterial conjunctivitis. Because the nasal and ocular mucosa tissues have a similar reaction to allergens, most patients with ocular complaints also have nasal symptoms. Among patients whose ocular symptoms appear isolated, mild nasal and/or lower respiratory symptoms can often be discovered during the patient interview.23
The ocular exam for allergy should focus primarily on the conjunctiva because the conjunctival membrane is an active immunologic tissue that responds to allergic stimuli.24 Papillary hypertrophy of the upper tarsal conjunctiva is a sign generally not observed in the SAC or PAC sufferer and indicates a more chronic and severe form of allergic conjunctivitis.1
Differential diagnosis of allergic conjunctivitis can be challenging because of the wide array of disorders that can mimic or mask the condition, including dry eye and meibomian gland disease (resulting in tear film abnormality or insufficiency), blepharitis, rhinitis and bacterial conjunctivitis.5
When the signs and symptoms are consistent with SAC and the patient history does not indicate some other disease, allergy testing is usually not required.25 However, in stubborn and recurrent cases, allergists can perform skin testing for specific allergens by scratch tests or intradermal allergen injections. In-vitro tests for allergen-specific IgE antibodies are also widely used.26 If a causative agent can be determined by either skin prick tests or allergen challenge, then avoiding the allergen can greatly lessen the severity and symptom frequency.
The management of ocular allergy includes patient education and allergen avoidance (if possible), topical therapies, and immunotherapy. Avoidance of the offending antigen is the primary behavioral modification for all types of allergic conjunctivitis. However, the eyes present a large surface area, so it is often impossible to avoid ocular exposure to airborne allergens. Sunglasses should be worn to reduce direct ocular exposure to airborne allergens. Treatment options will often depend on the symptom severity and the nature of the ocular allergy, and treatment should follow a stepwise approach.27
Following are three steps to design an allergy treatment plan.
Patients with mild, intermittent itching should use nonpharmaceutical measures like cold compresses, ice packs, and lubricating ophthalmic drops. Cold compresses provide relief from symptoms (especially itching). Artificial tear substitutes provide an allergen barrier and help to dilute the various allergens and inflammatory mediators present on the ocular surface-they help flush away these agents from the ocular surface. Alternatively, or concurrently, over the counter anti-allergy medications or an ocular antihistamine/mast cell stabilizer may be utilized.
Treatment with a topical ocular antihistamine/mast cell stabilizer is recommended for patients with itching (ranging from mild to severe and from intermittent to prolonged) who do not have significant redness or concurrent ocular conditions. However, steroids are commonly used. Corticosteroids remain among the most potent pharmacologic agents used in the more severe presentations of ocular allergy and are also effective in the treatment of acute and chronic forms of allergic conjunctivitis.
Treatment with a topical ocular antihistamine/mast cell stabilizer and/or a topical ocular corticosteroid is indicated for allergic conjunctivitis for seasonal allergy patients with moderate-to severe symptoms of allergic conjunctivitis and redness. Patients placed on a topical ocular steroid should receive careful follow-up to assess its effect and rule out adverse events, such as drug-induced intraocular pressure (IOP) elevation. IOP should be checked before steroid therapy is begun and rechecked at two weeks if the steroid is continued that long. A slit lamp examination of the ocular surface before steroid therapy should be done to rule out opportunistic infections (e.g., with herpes simplex virus or fungi).28 In severe cases, it may be necessary to get symptoms under control quickly by using a more aggressive approach and then reducing to a maintenance program. Many allergic conditions tend to be chronic in nature, so long-term control with agents such as mast cell stabilizers and antihistamines rather than a steroid may be preferred.
Allergen-specific immunotherapy is an effective treatment for patients with allergic rhinoconjunctivitis who have allergen-specific IgE antibodies. The main objective of this treatment is to induce a clinical tolerance to the specific allergen, which reduces the seasonal increases of IgE specific for that allergen. However, immune responses to allergen administration are not predictive of the therapy’s effectiveness. The therapy itself can produce systemic reactions, the incidence and severity of which can vary dependent on the type of allergen administered.29 Traditionally, immunotherapy is delivered via subcutaneous injection. However, sublingual (oral) immunotherapy (SLIT) is gaining momentum among allergists. Recent large-scale trials have focused on SLIT therapy for grass and ragweed allergies, and trials are underway using allergens from dust mites.30 SLIT requires further evaluation for ocular allergy relief; it has been shown to control ocular signs and symptoms, although ocular symptoms do not respond as well as nasal symptoms.31
The prevalence of allergies is increasing worldwide. Ocular allergies are a very common presentation in an optometric practice, especially in the spring of the year when the plants burst forth in bloom. Fortunately, with the treatment options available to eyecare practitioners, the prognosis for the disease is quite good. Familiarity with the condition and the many treatments available enable us to better care for our patients presenting with those itchy, watery eyes.
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