Dry Eye Disease vs Ocular Allergy

Dry Eye Disease vs Ocular Allergy

Dry Eye Disease vs Ocular Allergy

By Gary N. Foulks, MD, FACS

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Dry eye disease and ocular allergy are common conditions that are sometimes mistaken for one another. This is largely due to similarity in symptoms, as both conditions can cause irritation, redness, blurring of vision, and sensitivity to bright light. Compounding the confusion is the fact that an allergic episode can aggravate a concurrent dry eye disease, exacerbating dry eye symptoms that had been mild and tolerable. 

Differentiating Dry Eye and Allergy

It is important from a clinical standpoint, however, to distinguish between dry eye and allergy, as the conditions have very different mechanisms of action and are therefore managed differently. The old mnemonic, “If it itches it’s allergy; if it burns it’s dry eye,” is based in truth; however, one can’t rely solely on this distinction for diagnosis, as patients all describe symptoms differently.

A clinical examination is the starting point for the diagnosis of allergy and/or dry eye disease. Allergy patients often present with a papillary conjunctival reaction not necessarily present in patients with dry eye. Patients with allergy may also exhibit excessive mucous secretions, as well as changes to the skin around the lid margin.

Of course, an important distinction between allergy and aqueous-deficient dry eye disease is tear volume. While tears may be copious in allergy, the tear film is typically depleted in aqueous deficient dry eye disease—although, ironically, dry eye patients sometimes suffer bouts of epiphora. There is another exception to this distinction: patients who take allergy medicines, particularly systemic medicines, can exhibit a decrease in tear production due to the medication. If the patient already has borderline dry eye, the medication could be enough to make the patient symptomatic.

If the clinical examination does not reveal evidence of allergy, or if allergy is suspected as a comorbidity, a full dry eye workup can be performed to test the quantity and quality of the tear film and meibomian gland secretions.

Treating Two Conditions

Treating patients who have both allergy and dry eye can be challenging. Not only are patients dealing with two sources of discomfort, but treatment for one condition can sometimes directly exacerbate the other. As mentioned earlier, some allergy medications can diminish tear production, further drying the ocular surface. Conversely, punctual plugs for dry eye sufferers keep tears on the surface of the eye longer, but this means that allergens and histamine and other mediators they provoke also reside longer on the eye. In both cases, artificial tears can help; viscous tears can help restore moisture to the ocular surface when allergy medications have had a drying effect; and simple aqueous tears can help to flush the ocular surface when punctal plugs keep allergen-laden tears on the surface of the eye.

Contact lens wearers with dry eye and allergy must take care to clean lenses especially well. People with dry eye are more prone to depositing proteins and lipids on their lenses and these protein and lipid deposits can have a stimulating effect on an allergy-prone eye. For this reason, daily disposable contact lenses may be particularly attractive to contact lens wearers with both dry eye and allergy. Additionally, topical allergy medications with once-daily dosing are convenient for contact lens wearers and limit the number of times a preserved drop must be instilled into an already dry, irritated eye.

By correctly identifying both allergy and dry eye, clinicians can choose treatments that are effective for each condition, while being mindful of their treatment’s impact on a possible comorbid condition. 

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Gary N. Foulks, MD, FACS, is the Arthur and Virginia Keeney professor of ophthalmology, University of Louisville, KY, and is editor-in-chief of The Ocular Surface.