Point-of-care testing may improve accuracy of dry eye diagnosis

TAKE HOME MESSAGE: Joseph Tauber, MD, offers a critical appraisal of the role of available point-of-care tests for evaluating dry eye.

By Cheryl Guttman Krader; Reviewed by Joseph Tauber, MD

Kansas City, MO-Ophthalmologists should take a more proactive stance about identifying dry eye, as it is a common problem affecting visual function, quality of life, and the outcome of many ophthalmic surgical procedures.

Several point-of-care tests are now available to help with its diagnosis. Joseph Tauber, MD, described various modalities and provided his perspectives on their utility.

Further reading: Science, theory support nutritional influences on today’s dry eye disease

“The reasons to implement point-of-care testing are to improve the accuracy of diagnosis and communication with patients, and to obtain a metric for evaluation of therapeutic intervention,” said Dr. Tauber, medical director, Tauber Eye Center, Kansas City, MO. “Treating ocular surface disease is an art, and the focus is about making patients feel better.”

Weighing the options

A new blood test for Sjögren’s syndrome (Sjö, Nicox) is one example for which Dr. Tauber gave a “thumbs up.” The test-simple to perform in the office-includes three additional autoantibodies compared with standard serological screening and has higher sensitivity and specificity.

“One in 10 patients with dry eye has Sjögren’s, but the classic Sjögren’s antibodies are absent in 20% to 30% of patients with the disease, and the diagnosis is delayed for an average of almost 5 years,” he said. “This new blood test enables earlier diagnosis that will facilitate timely referral to appropriate specialists and discussion of disease-related risks.”

Dr. Tauber said he also had a favorable opinion of tear osmolarity testing (TearLab, TearLab Corp.), which improves the sensitivity and accuracy of dry eye diagnosis and identifies a treatable problem. The result is interpreted as “positive” if the tear osmolarity is >308 mOsms/L or if the inter-eye difference exceeds 8 mOsms/L.

Reviewing published studies investigating tear osmolarity testing, Dr. Tauber concluded that the evidence indicates it is a reliable metric for evaluating progression of disease and for monitoring treatment response.

An assay for matrix metalloproteinase-9 (MMP-9) (InflammaDry, Rapid Pathogen Screening) measures the level of that proteolytic enzyme in a tear film sample. The test reads “positive” if the MMP-9 concentration is ≥40 ng/mL.

Measurement of MMP-9 identifies risk and a treatable problem, i.e., inflammation. However, since MMP-9 is produced by epithelial cells in response to stress, its level in the tear film may be elevated in a variety of ocular surface diseases, and there is only limited evidence to indicate the tear film assay is a reliable metric for dry eye, he noted.

“Any benefit of this test in clinical practice is uncertain,” Dr. Tauber said. “There is no evidence that it differentiates between aqueous deficiency and evaporative dry eye, and perhaps its greatest value is when the result is negative, as that is an indication the patient is unlikely to have clinically significant dry eye.”

Discussing the use of an interferometer for analysis of the tear film lipid layer (LipiView, TearScience), Dr. Tauber said it provides clinically relevant information that seems to be fairly reproducible, although there are no published data evaluating its performance in that regard. The measurement takes about 20 seconds, and a numerical result is generated that is interpreted as follows: normal (>90); may warrant treatment (≤90); or 90% likelihood of having meibomian gland dysfunction with ≤4 expressible glands (≤60 nm). Perhaps even more useful, the device also reports the number of partial blinks during the measurement period.

“I am struck by how many patients have what I call ‘dysfunctional blink syndrome’ and are failing to fully spread lipid over the ocular surface because of partial blinks,” he said.

Another multifunction device is a corneal topographer that also provides meibography, quantifies the tear meniscus, grades ocular redness, and does an automated assessment of tear film breakup time and location (Keratograph 5M, Oculus). While the machine does not quantitate meibomian gland dropout, it does generate an image that allows the clinician to visualize the gland anatomy quite well, Dr. Tauber noted.

A device measuring tear film lactoferrin (TearScan, Advanced Tear Diagnostics) is being promoted as useful for identifying aqueous deficiency disease. Although results from studies conducted by the manufacturer indicate that it has reasonable sensitivity (83%) and high specificity (98%), those findings have not been replicated by others. Dr. Tauber suggested that more data are needed to establish the reliability of this test.

Joseph Tauber, MD

E: jt@taubereye.com

This article was adapted from Dr. Tauber’s presentation at Cornea Subspecialty Day during the 2014 meeting of the American Academy of Ophthalmology. Dr. Tauber has no financial interest in any of the products discussed. He has been an investigator in clinical trials and a member of the advisory board for several companies that market products for treatment and evaluation of dry eye disease.