SPOTLIGHT ON TECHNOLOGY & TECHNIQUE

Finding DED in likely (and unlikely) suspects

The TearLab Osmolarity System is used to tell real cases of dry eye from “imposters.”

By Robert Stoneback, Associate Editor

In the years since its introduction, the TearLab Osmolarity System has been tested for ways it could contribute to helping patients.

This past August, researchers used TearLab in a study examining its use in preparation for cataract surgery patients. They concluded that measuring tear osmolarity when planning such surgery can help identify patients with a higher chance of refractive error due to inaccurate keratomery.^*1

It’s a good idea to test any presurgical patient for osmolarity levels, according to Jay Pepose, MD, director of the Pepose Vision Institute, TearLab Corporation Consultant and professor, clinical ophthalmology and visual sciences at Washington University School of Medicine. At his practice, he uses TearLab on all upcoming LASIK and cataract surgery patients.

The TearLab Osmolarity System uses electronic “pens” to sample and analyze a patient’s tears.

Another test, conducted in April 2014, found TearLab could be used to measure the osmolarity of salt solutions, including high osmolarity liquids of up to 400 mOsm/L.²

DIAGNOSING DRY EYE QUICKLY AND ACCURATELY

While dry eye disease is a common ailment, some people who have it may not even realize it. About half of patients who have dry eye disease show no symptoms of it, according to Dr. Pepose.

Due to this poor correlation between signs and symptoms of dry eye, many who would be diagnosed with dry eye are missed and no treatment initiated. In contrast, some patients may have complaints of dry eye-like symptoms, such as grittiness, foreign body sensation, or dryness, but do not have the ailment.

Dr. Pepose referenced an article written by Paul Karpecki, OD, which listed possible dry eye “imposters” with similar symptoms, including conjunctivochalasis, anterior blepharitis and asthenopia.³

Accurate identification is even more important as there is a high prevalence of hyper-osmolarity across the country, says Dr. Pepose. A recent study in which he assisted examined more than 9,000 patients across 150 U.S. examination sites. The testing found that 48% had an osmolarity rating greater than 308 mOsm/L, consistent with dry eye disease.

HOW IT WORKS

TearLab takes a sample from the eye’s tear meniscus. The amount of tears it retrieves is very small, only about 50 nL, but it is enough to perform an osmolarity analysis and check for signs of dry eye. Two electronic “pens” are included with the TearLab, with “test cards” attached to the end of each. These can be used to take samples from each of a patient’s eyes. When the pens are placed on the TearLab’s reader, it will display the osmolarity level of each sample.

Tear osmolarity greater than 308 mOsm/L is seen as mild dry eye disease, above 320 mOsm/L is moderate and severe is 340 mOsm/L. It’s important to pay attention to the osmolarity difference between the eyes as well, as a variation of 8 mOsm/L or greater indicates a loss of homeostasis; a dry eye warning sign, says Dr. Pepose.

In his experience, false positive results from the TearLab are rare.

While tear osmolarity is an important component in diagnosing dry eye, it is not a substitute for a careful review of the patient’s medical history and additional examinations. These are important to determine the etiology of the dry eye syndrome and to design an appropriate treatment.

OSMOLARITY TESTING IN THE FUTURE

Tear osmolarity, like blood osmolarity, is tightly regulated in the body, and variations in its level can indicate problems.

Dr. Pepose expects that tear testing in the near future will be used to test for multiple factors such as markers of allergy or inflammation, and will become “a little more congruous with going to an internist.”

Testing people for dry eye early, particularly after anterior segment surgery, saves them from becoming unhappy patients later, Dr. Pepose says. At the end of the day, happy patients bring in more happy patients. OM

*Four of the researchers received payment from TearLab.

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