5 Myths About Ocular Allergies

Brianne N. Hobbs, OD

Disclosures

December 05, 2017

The terms ocular allergy and allergic conjunctivitis are often used synonymously because the conjunctiva is often the most prominent ocular tissue involved in the allergic response. Allergic conjunctivitis is very common. One large epidemiologic study[1] found that up to 40% of the US population has been affected at some point. Despite its prevalence, several myths about the clinical management of this condition persist. This article will identify these misconceptions so that clinicians can more effectively treat patients with allergic conjunctivitis.

Myth 1: Allergic Conjunctivitis Is Always Seasonal

There are several different common forms of allergic conjunctivitis: seasonal, perennial, vernal, and atopic, in addition to more rare forms.

While seasonal allergic conjunctivitis (SAC) does have the classic bimodal occurrence with symptoms peaking in the fall and spring, those suffering from perennial allergic conjunctivitis (PAC) often experience milder symptoms year-round. Both SAC and PAC represent type 1 hypersensitivity reactions, which are characterized by an immediate release of histamine upon exposure to the allergen that is mediated by immunoglobulin E.

Vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) are considered to be chronic conditions and have a different pathophysiology from SAC and PAC. VKC and AKC both exhibit components of immediate and delayed hypersensitivity reactions.[2]

Although it is not necessarily imperative to differentiate SAC from PAC as the treatments are largely similar, it is important to distinguish the more severe forms of VKC and AKC.

Myth 2: Systemic Treatment Adequately Controls Ocular Symptoms

Approximately 40%-80% of patients with allergies have ocular symptoms, and sometimes ocular symptoms are the only indication of allergies.[3,4] Over half of nasal allergy sufferers responded in a survey that ocular symptoms were bothersome.[1]

Randomized trials have shown that topical medications, such as olopatadine[5] and ketotifen,[6] are more effective than oral medications in controlling ocular symptoms. Oral allergy medications, such as antihistamines, can have adverse effects on the ocular surface, including dryness and decreased tear production, thus exacerbating a patient's ocular symptoms.[7] In addition to superior ocular symptom relief, treating with topical medications can help prevent a chronic inflammatory reaction.[8]

Myth 3: Allergic Conjunctivitis Is Only Common in Certain Regions of the United States

Allergies are a common problem in the United States. The Centers for Disease Control and Prevention estimates that more than 50 million Americans of all ages suffer from allergies.[9] Every region of the United States has specific allergens—even the desert southwest. Allergens are unique to the region, and many different substances beyond the commonly recognized pollen can serve as allergens. PAC is often caused by mold, dust mites, cockroaches, pet dander, or other environmental allergens[10] that are often present regardless of the geographic region.

Myth 4: All Papillae Are Created Equal

The conjunctiva is the perfect place to look for signs of allergies. The conjunctiva is a highly vascularized tissue that has near constant exposure to the environment. Additionally, the conjunctiva is home to a large number of cells active in the immune response. The combination of these three factors—vascularization, exposure, and immune cells—makes the conjunctiva especially sensitive to the effects of allergens. Both the bulbar conjunctiva and the palpebral conjunctiva may have evidence of an allergic response. The bulbar conjunctiva typically exhibits injection and chemosis, while the palpebral conjunctiva shows evidence of an allergic response predominantly through the formation of papillae.[2,11]

The size, location, and quantity of papillae are useful in distinguishing among the types of allergic conjunctivitis.

Giant papillary conjunctivitis, defined as conjunctivitis with papillae measuring larger than 1 mm, is often caused by mechanical irritation from a contact lens, exposed suture, or other irritant.[11] Fine papillae can be present in those suffering from SAC and PAC but do not reach the "cobblestone" appearance that is characteristic of VKC.[2]

The presence of papillae does not always necessitate treatment. Sometimes papillae are found in asymptomatic patients, especially if they are only located medially or laterally on the palpebral conjunctiva.[2]

Myth 5: Itchy Eyes Are Always Caused by Allergies

While itching is a common symptom of allergic conjunctivitis, particularly if the patient is symptomatic in both eyes, itchy eyes can also be caused by dry eye.

Inquiring about the presence of coexisting allergic rhinitis is often helpful in distinguishing between allergic conjunctivitis and dry eye syndrome.[12] Typically, watering eyes are suggestive of allergies, while burning eyes are more indicative of dry eye.[12]

Although allergic conjunctivitis and dry eye syndrome are distinct clinical entities, both of these conditions can often benefit from artificial tears. Artificial tears can help reduce the concentration of allergens in the tear film, thus reducing the intensity of the allergic response.[12] The lubrication offered by artificial tears can also reduce symptoms of allergic conjunctivitis.

Take-Home Messages for Clinicians

Allergic conjunctivitis is a common condition that can affect patients of all ages, but it is often underdiagnosed. Only 10% of individuals with ocular allergy symptoms seek medical attention.[13]

A careful patient history and a detailed anterior segment examination are needed to diagnose allergic conjunctivitis.[13] Prompt treatment can alleviate symptoms and improve quality of life for patients who might have otherwise suffered in silence.

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