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How to differentially diagnose and treat dry eye, allergy
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Dry eye is one of the most common ocular surface abnormalities, occurring in 11% to 22% of the population. It occurs when the tear film has a deficiency in one or more of its components and is a primary disease of the ocular surface or, more rarely, secondary to diseases such as rheumatoid arthritis. Dry eye is more common in individuals older than 55 years of age, particularly women, and can be more severe in contact lens wearers.
Dry eye results from a dysfunction in the tear aqueous, lipid or mucin. Sjögren’s syndrome, senile post-menopausal hyposecretion, long-term contact lens wear and intake of systemic drugs, such as antihistamines, are all associated with aqueous tear disorders.
Deficiency of the lipid layer is the result of malfunctioning meibomian glands, leading to excessive evaporation of aqueous tears. This occurs most frequently in blepharitis, but can also be observed in allergic disorders such as atopic keratoconjunctivitis (AKC) or vernal keratoconjunctivitis (VKC) and giant papillary conjunctivitis, with non-specific irritation or with chronic instillation of drugs.
A mucin deficiency directly relates to goblet cell pathology and occurs in chronic inflammation. Secondary factors such as arid weather, air conditioning, heating, lack of hydration and medications can greatly exacerbate the symptomatology associated with these underlying conditions.
Dry eye vs. allergy
Certainly of great importance in identifying the source of a patient’s red eyes is an accurate history aimed at answering some critical questions. Identify quickly if the problem is allergic in nature:
- l Do you, your parents or other family members have allergies or a history of allergy?
- l Do you ever have episodes of intense itching, along with varying degrees of tearing, redness and swelling related to specific activities?
- l Do you ever use eye drops for itching or redness?
- l Do you use oral antihistamines at any time of year?
Questions then need to be aimed at dry eye phenomena:
- l Are symptoms more noticeable when you are reading, watching television or using the computer (when the blink rate decreases)?
- l Are symptoms worse under certain climactic conditions, such as central air conditioning, forced hot air heating or very dry weather?
Signs and symptoms
Dry eye and ocular allergy have many common features that can muddle their diagnosis. First, burning characterizes dry eye, while itching characterizes allergy, yet the nature of the discomfort is not always clear from the patient’s description. Additional “watchwords” for dry eye are dryness, grittiness and especially “tired eyes” or ocular fatigue.
For allergy, patients complain of swollen or puffy eyes (especially from women who notice swollen lids), eyes at half-mast and a “hot, tight” feeling, although this is usually more indicative of AKC or VKC. Notably, the absence of itching differentiates allergy from dry eye. In fact, itching is the only mandatory diagnostic feature unique to allergy.
It can be very helpful to question the patient as to what happens when he or she rubs his or her eyes. With dry eye, rubbing can stimulate reflex tear secretion and relieve some discomfort. With allergy, rubbing will make patients feel worse because it increases mast cell degranulation.
Both allergy and dry eye have tearing. With dry eye, it is the more sporadic reflex tearing that occurs following discomfort, usually in the evening or when tired. With allergy, tearing is a relatively constant reflex for flushing away allergens. Thus, it is important to ask the patient when he or she has tearing. The answer can point to dry eye or allergy.
Lid crusting in the form of flaky skin around lids, the presence of collarettes or seborrheic signs classically associated with blepharitis can point to dry eye. If lid crusting involves excess mucus, it is more indicative of allergy. Lid swelling, if present in dry eye, is usually mild, while an acute allergic stimulus can cause a flagrant lid reaction in some individuals.
Systemic symptoms lead a clearly divergent path: patients having severe dry eye can also have dry mouth and rheumatopathies. Allergy is often associated with nasal congestion, sneezing, wheezing, post-nasal drip or an itchy throat.
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Clinical Signs and SymptomsDry eye questionnaires
While I do not regularly use questionnaires because of the large amount of paperwork already burdening patients with each visit, I do advocate their use for the occasional difficult diagnosis. In such cases, I find the OSDI (Ocular Surface Disease Index) useful. This well-documented form quickly provides a quantified result with diagnostic information. You can obtain copies of this form from your Allergan sales representative.
The DEQ (Dry Eye Questionnaire) and DEQLQ (Dry Eye Quality of Life Questionnaire) are also helpful. Any questionnaire that is quick, accurate and specific to dry eye could be valuable in its differential diagnosis and, particularly, in follow-up to determine if a patient is experiencing any improvement with instructions or therapies that have been dispensed.
Information on the DEQ can be found at research.opt.indiana.edu. The DEQLQ is still under investigation. Pollard and colleagues reported at the Association for Research in Vision and Ophthalmology meeting this year that “the DEQLQ demonstrated an ability to significantly discriminate between a population of normals and patients diagnosed with dry eye.”
Slit-lamp biomicroscopy
Allergic lids will be swollen, with a flushed, velvety appearance when everted, and possibly with pseudoptosis or mild papillae, although these are typically only present in the more severe forms of allergy. Dry eye lids will have more blepharitic symptoms, such as scaling, collarettes, lash loss and meibomian gland dysfunction.
An assessment of the lipid secretions across the lid margins, where an oily consistency is normal and a buttery secretion pathological, is essential in differentiating blepharitis from aqueous-deficient dry eye. Other chronic inflammations such as superior limbic keratoconjunctivitis, rosacea and low-grade bacterial or chlamydial infections may all impair tear film stability. Remember that any associated skin abnormality such as rosacea or seborrheic blepharitis can contribute to a dry eye state.
The conjunctiva in allergy is edematous, appearing “boggy” with a pinkish inflammation in the caruncle and media canthus due to pro-inflammatory mediator accumulation and, subsequently, increased rubbing in the corners of the eye. Conversely, the conjunctiva in dry eye has a diminished luster, actually appearing dry. Typically, also present are increased hyperemia and vascularity, lissamine staining in the band region of the bulbar conjunctiva, a decreased lacrimal lake and aqueous tears.
The cornea in advanced cases of dry eye can have inferior staining, mucous filaments/strands, debris in the tear film and a dry ocular surface. The cornea is typically uninvolved in allergy. The only exceptions are in the presence of chronic eye rubbing; patients may have staining in the inferior region of the cornea due to “knuckle keratopathy.” In very advanced cases of severe allergy, shield ulcers can occur.
Tear film break-up time
Tear film break-up time can be useful but is not always conclusive in the diagnosis of dry eye. Some patients who have adequate tear film break-up still have dry eye symptoms, and vice versa. It is best used as supporting, rather than conclusive, evidence of dry eye. Schirmer’s strips can be extremely variable and are more appropriately used in research instead of the clinic.
When dry eye, allergy co-exist
In the event that both conditions exist in a patient, treatment with the most comfortable and lubricating anti-allergic agent will soothe the dry eye as well as treat the ocular allergy. There is no evidence that ocular antihistamines cause surface drying. In fact, olopatadine, a dual-action antihistamine and mast-cell stabilizer, was shown to actually improve tear function and ocular surface status with regard to squamous metaplasia and loss of goblet cells (Dogru M, Ozmen A, Erturk H, Sanli O, Karatas A. Changes in tear function and the ocular surface after topical olopatadine treatment for allergic conjunctivitis: an open-label study. Clinical Therapeutics. 2002;24(8):1309-1321). Anti-allergy therapy can be supplemented with preservative-free tear substitutes.
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Dry eye-related redness: Although common to many conditions, redness in dry eye is typically a subtle redness limited to the interpalpebral fissure. Additional diagnostic tests and queries to the patient can confirm the diagnosis. |
In cases of mixed or “indiscriminate” ocular surface disease, the use of a non-preserved artificial tear such as Systane PF (Alcon) can be very helpful, because lubrication can have a profound effect on alleviating symptoms in both dry eye and allergy.
When the diagnosis of dry eye is certain, and there is significant irritation and surface damage, Systane can again be incredibly effective. Research has shown that the components in Systane help “bandage” the cornea temporarily, allowing for restoration of the normal epithelial glycocalyx. Of course, oral antihistamines and topical vasoconstrictor agents should always be avoided, as these have definitively been shown to exacerbate dry eye problems.
Restasis (cyclosporine, Allergan) can be very beneficial in certain patients, and it has also been shown to be effective for acute allergic conjunctivitis. Velasco and colleagues reported at the 2003 ARVO meeting that “the management of allergic conjunctivitis with topical cyclosporine A has a satisfactory evolution in 83.3% of patients, with 50% [having] symptomatic relief within the first week of treatment.”
Doxycycline is extremely helpful in patients with advanced meibomian gland disease. Punctal occlusion works very well in patients who have dry eye secondary to either environmental issues or contact lenses. However, if the dry eye is related to inflammatory disease or, worse, if it is related to allergy, avoid punctal plugs because it increases the contact time between the inflammatory mediators in the tear film and the eye.
A final consideration for severe, symptomatic surface disease would be a mild topical corticosteroid. Steroids are now used widely in the initial management of both allergic conjunctivitis and dry eye. They can provide a great deal of symptomatic relief, blocking inflammation in a relatively short time. However, practitioners must realize that prolonged use of steroids can have significant ocular sequelae. These agents are for short-term use only; ultimately, the clinician must discover the true etiology of the disorder and address it appropriately.
For Your Information:
- Alan G. Kabat, OD, FAAO, is associate professor/director of residency programs at Nova Southeastern University College of Optometry in Fort Lauderdale. He can be reached at 3200 South University Drive, Ft. Lauderdale, FL 33328; (954) 262-1470; fax: (954) 262-1818. Dr. Kabat is a member of Alcon’s Speaker Alliance. He has no direct financial interest in the products mentioned, nor is he a paid consultant for any companies mentioned.