Though El Niño tempered this year’s winter weather in parts of the country, the promise of spring is still an inviting one. For many patients, spring means warmer temperature and more daylight—and more time spent outdoors. As such, spring can also mean an exacerbation of the itchy, red and watery eyes commonly associated with seasonal allergic conjunctivitis. While “allergy season” is often attributed to the increased presence of airborne pollen in the spring, many symptomatic patients continue to present into summer and autumn, depending on local climate and temperature.
Allergic conjunctivitis may not be the only culprit responsible for seasonal discomfort, however: recent research still indicates a clear seasonal pattern with respect to presentations of dry eye, as the condition was most common in the winter and spring and least common in the summer.1 The pattern was ascribed to low humidity in the winter and seasonal allergens in the spring; as such, the findings suggest allergy may not be the only factor in seasonal eye disease.
When an affected patient presents to the clinic, clinicians must ask: Is it allergy or dry eye—or both? Reviewing the epidemiology, clinical examination and treatment of both allergic conjunctivitis and dry eye can further our understanding of these coexisting conditions and help clarify a diagnosis. Additionally, recognizing how each can present clinically and identifying which patients are most likely to be affected can help guide providers in tailoring the treatment regimen to the individual patient.
Differentiating between dry eye and allergic conjunctivitis can take some effort. Which one is present here?
Defining the Condition
The International Dry Eye Workshop (DEWS) classified dry eye as a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability that may cause damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.2 Similarly, the committee identified allergic conjunctivitis as an extrinsic cause of dry eye. In their model, conjunctival and corneal irregularities (e.g., punctate keratitis and shield ulcers) can destabilize the tear film and contribute to dry eye.2,3 In chronic disease, meibomian gland dysfunction further contributes to dry eye by interfering with the lipid layer of the tears.
These definitions suggest that the two conditions share elements of the underlying disease process and reinforce that inflammation is a key component of both. For example, a past study of allergic conjunctivitis reported that patients with itchy eyes were more than twice as likely to experience dry eye as patients with non-itchy eyes.4 As such, significant symptoms of itching in conjunction with dry eye may also suggest coexisting atopic disease. Patients with allergic conjunctivitis who exhibit disruptions in tear film integrity, symptoms of burning or both may also be suffering from coexisting dry eye disease.
Patterns of Prevalence
Although it’s difficult to isolate the affected populations for conditions as common and multifactorial as allergy and dry eye, some epidemiologic patterns have been documented in the literature.
• Allergic Conjunctivitis. Conventional wisdom holds that approximately 15% to 20% of the United States population suffers from ocular allergy.5 However, 40% of the participants in the third National Health and Nutrition Examination Survey reported symptoms of ocular allergy at least once during the previous year.6 Older allergy suffers (those above age 50) were more likely to report isolated ocular symptoms, while younger suffers were more likely to report nasal and ocular symptoms. This observation is consistent with the present understanding that dry eye tends to increase with age while symptoms related to atopy tend to decrease with age.6 It’s also noteworthy that seasonal and perennial allergic conjunctivitis is often present in both genders from childhood through middle age, while vernal keratoconjunctivitis is more likely to present in young males under the age of 18 years.7 Allergic conjunctivitis is often associated with nasal symptoms and history of prior allergic events.8
• Dry Eye. This condition has been reported in 5% to 30% of the population. Variations in these estimates may be the result of differing diagnostic criteria across studies. Importantly, low estimates may reflect patients with moderate to severe disease while high rates may also include patients with more mild forms of the condition.9 Large studies of dry eye, including the Women’s Health Study and the Physician’s Health Study, estimate that nearly five million Americans age 50 or older suffer from moderate to severe dry eye, with approximately twice as many women as men presenting with the condition.10,11 In addition to female gender and older age, other reported risk factors for dry eye include LASIK and refractive excimer laser surgery, connective tissue disease, antihistamine use, radiation therapy, hematopoietic stem cell transplantation, vitamin A deficiency, hepatitis C infection and androgen deficiency.9
Identifying the Culprit
Symptoms of allergic conjunctivitis include tearing, itching, burning, foreign body sensation and dryness. The clinical exam should begin with a thorough case history, followed by a careful physical evaluation. A personal or family history of atopic disease is common and may occur in isolation or with nasal symptoms. Signs of allergic conjunctivitis include conjunctival hyperemia and chemosis, papillae, lid edema and watery discharge.
While pollen is a trigger of seasonal allergic conjunctivitis, other environmental irritants such as pet dander and mold can also exacerbate symptoms. The presence of large papillae at the upper tarsal conjunctiva or limbus is a hallmark of the vernal form of the disease.
If itching is considered the hallmark symptom of allergy, then burning and foreign body sensation are preeminent symptoms of dry eye. While there is variation in clinical practice, most clinicians use a variety of measures to diagnose dry eye. Clinical observations typically include severity and frequency of ocular discomfort, visual symptoms like fluctuating vision, conjunctival and corneal staining, conjunctival injection and disruptions in tear film quantity, quality or both. Common measures of health and tear film integrity include tear break-up time, tear meniscus, Schirmer’s or phenol red thread test and rose bengal or lissamine green. Less commonly available measures include tear osmolarity and impression cytology.
Examination typically includes lids and lashes due to their direct influence on the tear film. Recently, this examination includes surveillance for Demodex due to the association of these mites with meibomian gland dysfunction. While Demodex is difficult to view during a standard biomicroscopic exam, clinicians should be aware that cylindrical dandruff at the base of the lash and peculiar skin debris are associated with the condition.2
Point-of-care tests like matrix metalloproteinase 9 (MMP-9), while non-specific, can be used to support a diagnosis and to identify patients who would benefit from anti-inflammatory therapy.12 Similarly, tear osmolarity testing can be used for both initial diagnosis and for monitoring the treatment response of patients with dry eye.
The two traditional classifications of dry eye—aqueous tear-deficient and evaporative dry eye (intrinsic and extrinsic)—are based upon etiology.13 However, recent work suggests that as dry eye progresses, hybrid forms of the condition can develop.14 Identification may require the practitioner to prescribe additional treatment modalities to address the spectrum of disease. Thus, advanced aqueous-deficient dry eye includes meibomian gland dysfunction and vice-versa. Furthermore, there has been a shift in emphasis from the aqueous-deficient model of dry eye to a lipid-deficient evaporative dry eye model that is associated with meibomian gland dysfunction. As a result, current treatments emphasize the strategies typically recommended for evaporative dry eye.
Treating the Disease
Clinicians and patients are fortunate to have a multitude of treatment options that range from simple lifestyle adjustments and home remedies to over-the-counter or prescription medications:
• Allergic Conjunctivitis. Avoidance of the allergen, cool compresses and preservative-free lubricants may suffice for some patients. When these non-pharmacological treatments are inadequate, topical antihistamines, mast-cell stabilizers and nonsteroidal anti-inflammatory agents make up the mainstay of treatment for allergic conjunctivitis due to their efficacy and safety profile. Short-term judicious use of steroids for patients with severe allergic conjunctivitis is commonly advocated when other treatments are inadequate. Newer corticosteroids provide significant relief with fewer side effects (e.g., ocular hypertension, cataract and infection), but still require supervision by an eye care provider.
Contact lens wear may require modification depending on its association with symptoms of allergic conjunctivitis. Lens wear may even need to be discontinued temporarily. Reducing lens wearing time, increasing lens replacement frequency (in particular, advocating single-use lenses during allergy episodes) and prescribing a preservative-free lens care regimen are management options for mild to moderate presentations of allergic conjunctivitis.
• Dry Eye. Often, signs and symptoms of dry eye do not correlate. This requires the clinician to take a holistic approach in assessing disease severity and initiating treatment. Treatment regimens can then be modified based upon the patient’s initial response. Preservative-free artificial tears, gels and ointments are the mainstay of dry eye treatments. In addition to tear supplements, management often includes modification of the environment (e.g., adjustments to humidity and temperature) and treatment of any complications like punctate keratopathy, filamentary keratitis or vision problems.
Cyclosporin A has traditionally been indicated to suppress inflammation in the aqueous-deficient form of dry eye. In contrast, evaporative dry is managed using therapies that target meibomian gland dysfunction such as gland expression and heat application. Eyelid scrubs and mechanical devices like LipiFlow (TearScience) can also help manage evaporative dry eye. Treatment may also include topical or oral antibiotics with anti-inflammatory properties. As with allergic conjunctivitis, topical corticosteroids may also be used for short-term therapy to increase overall treatment efficacy.
Adjunctive therapy may include nutritional support (i.e., ingestion of fish oil and omega-3 fatty acids to reduce inflammation) and patient education regarding avoidance of preservatives and other environmental irritants. Tea tree oil treatments and lid scrubs have been advocated to eradicate Demodex and ocular inflammation associated with this condition.15 While mild dry eye may benefit from the previously described modifications in contact lens wear, scleral lenses have been used successfully as a treatment option to ameliorate the signs and symptoms of moderate to severe dry eye.16
Additionally, there are a number of emerging treatments for both dry eye and allergic conjunctivitis. These build on existing treatment regimens and our understanding of the immunopathophysiology for both diseases. With the recognition that dry eye and allergic conjunctivitis coexist, pharmaceutical management can target both diseases.15,17 Future treatments will likely target ocular surface inflammation with fewer side effects than with traditional glucocorticoids.18
It is important to differentiate between these two overlapping conditions, considering both have significant health indications. They are commonly encountered in clinical practice and have the potential to impair quality of life and incur significant health care costs from professional services, therapies and pharmacological treatments.5,6,9,19-23 Recognition of the coexistence of dry eye and allergic conjunctivitis allows the eye care provider to treat the presenting problem more effectively. For example, dry eye treatments in the winter months could emphasize lubricants, while treatments in the spring and summer could incorporate anti-inflammatory agents.1
Perhaps most important, treatment options for one condition can actually worsen the coexisting condition. Case in point: allergic conjunctivitis treatments that emphasize the use of oral antihistamines may exacerbate dry eye symptoms.
Dry eye and allergic conjunctivitis can mean “double trouble.” When the eye is dry, allergies tend to be worse, and the converse is also true. Therefore, clinicians should also be vigilant in their surveillance of dry eye and allergic conjunctivitis as comorbidities and modify treatment options accordingly to address each in the best way possible.
Dr. Wagner is a professor of clinical optometry at Ohio State University, where she also serves as the director of extern programs. She is a diplomate in the Cornea, Contact Lenses and Refractive Technologies Section of the American Academy of Optometry and a member of the American Optometric Contact Lens Educators, the American Optometric Association and the Association for Research in Vision in Ophthalmology.
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