Diagnosing dry eye: Assessing value of point-of-care tests Motivation for using any of the new technologies is to provide better patient care February 15, 2015By Cheryl Guttman Ophthalmologists should be proactive about identifying dry eye because 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 the diagnosis. Joseph Tauber, MD, described the various modalities and provided his perspectives on their utility."The reasons to implement point of care testing are to improve the accuracy of diagnosis, our 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."Dr. Tauber gave a "thumbs up" to the new blood test for Sjögren's syndrome (Sjö, Nicox). Easy to perform in the office, the test includes three additional autoantibodies compared to standard serological screening and has higher sensitivity and specificity."One in 10 dry eye patients 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 also had a favorable opinion of tear osmolarity testing (TearLab, TearLab Corporation), which he said 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 intereye 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.Dr. Tauber said 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 a reliable metric for dry eye."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), 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 their partial blinks," Dr. Tauber 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). Dr. Tauber noted that 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. 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
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