Distinguishing dry eye from ocular allergy: Careful history-taking should tell the story

Initially, dry eye and allergy symptoms may appear similar. Listening carefully to how patients describe their conditions is key to diagnosis.

ByJeanne Gonzalez

Dry eye and ocular allergy are two common, intermittent ocular conditions, and in both the primary complaint is patient discomfort. The key to distinguishing ocular allergy from dry eye is careful history-taking, according to two cornea specialists.

“This is an age-old problem that was difficult to differentiate without careful evaluation of history. The signs and symptoms can look similar at first,” Mark B. Abelson, MD, told Ocular Surgery News.

“The waters are frequently muddy,” agreed Jeffrey P. Gilbard, MD, “but with a careful history, even before you put the patient’s head in the slit lamp you should have a good idea if this patient is going to have dry eye or allergies.”

Ocular allergy affects about 20% of people and dry eye about 12%, Dr. Abelson said. Both conditions are intermittent, and they overlap, so misdiagnoses can and do occur, he said. Patients with dry eye may describe symptoms hinting at ocular allergy, and vice versa.

But asking the right questions, and rephrasing when necessary, should reveal the diagnosis even before the patient is examined, Dr. Abelson said.

“The physician should be able to diagnose based on a well-controlled, 1-minute history confirmed with a brief slit-lamp exam,” he said. “The short answer is, if it itches, it’s allergy, and if it burns, it’s dry eye.”

Dry eye patients typically describe burning, sandy, gritty sensation, and their symptoms tend to worsen throughout the day, Dr. Gilbard said. “Sometimes they may have very mild symptoms of itching. The key word here is ‘mild’,” he said.

Those with ocular allergy tend to have intense itching, redness and swelling of the lids, Dr. Abelson said.

He said it was important to listen to patients and how they express their problem. Occasionally, patients will describe what sounds like dry eye symptoms but also mention itching. He then asks another question to clarify what the patient is saying.

“Be careful in your selection of words, and ask another question to clarify. … History-taking is still the core of diagnosis,” he said.

Intensity of itching

Dr. Gilbard said that if the patient’s description of symptoms is ambiguous, he focuses on the intensity of the itchy feeling.

“Occasionally, you’ll get a patient with dry eye that complains about itching. The question to ask is whether it itches like a mosquito bite. If you don’t clear that bar, it can still fall within the range of dry eye. The folks with allergy will say ‘yes,’ it does itch like a mosquito bite. It’s that kind of intense itching, whereas in dry eye it can be a more mild itch,” he said.

When does it happen?

The next question to consider is the timing of the symptoms. Because dry eye syndrome can develop as a result of environment, the physician should ask patients about where they work and live. Air conditioning, fatigue and wind with particulate matter are some of the contributing factors, Dr. Abelson said.

A family history of conditions such as eczema and asthma may indicate atopic allergy, Dr. Gilbard said.

Patients with allergy are affected by seasonal factors or allergens that are not linked to time of day as with dry eye syndrome, Dr. Gilbard said. Dry eye patients’ symptoms tend to get worse as the day goes on.

The use of certain antihistamines and other drugs may be associated with dry eye syndrome, Dr. Abelson said. Patients with Sjögren’s syndrome, immune disease or thyroid disease, and women experiencing menopause are also at an increased risk for developing dry eye syndrome.

Although these factors are not always crucial to a diagnosis, knowing about them may help. For these reasons, Dr. Abelson said, he always asks if a patient has dry mouth, a cornerstone symptom of Sjögren’s syndrome.

The physical examination

There are many tests available, Dr. Abelson said, but slit-lamp examination should be sufficient to confirm the diagnosis that the physician suspects after taking the patient’s history. Decreased tear film is the typical sign of dry eye syndrome. Ocular allergy generally manifests as lid swelling, redness and itching, he said.

For the diagnosis of dry eye, Dr. Gilbard looks primarily to the history. “Sandy-gritty irritation, burning, dryness or increased awareness of the eyes that gets worse as the day goes on is more sensitive than any feature on examination or any diagnostic test. I use the examination to determine why the patient has dry eye, rule out potentially confounding diagnoses and stage the disease,” Dr. Gilbard said.

Dr. Abelson said he performs a noninvasive tear film breakup test on most patients. He instructs patients to keep their eyes open and count the seconds until they feel burning.

“If it’s after 7 seconds, you’re fine; if it’s before, you’re not,” he said.

He also calculates what he called the ocular protection index (OPI), which relates the interval between blinks to the tear film breakup time. The normal blink rate is about every 7.7 seconds. If the blink rate is slower than the tear film breakup time, some adjustment may be needed.

The OPI makes patients aware of their blink rate, Dr. Abelson said, and is useful in educating patients about the pathology.

For Your Information:

Mark B. Abelson, MD, can be reached at 863 Turnpike St., North Andover, MA 01845 U.S.A.; +1-978-685-8900; fax: +1-978-685-0020; e-mail: mbabelson@oraclinical.com.

Jeffrey P. Gilbard, MD, can be reached at Baldwin Park I, Suite 200, Woburn, MA 01801 U.S.A.; +1-781-932-8327; fax: +1-781-935-5075.