Point-of-Care Tests: What Are You Measuring?
Measuring lipid thickness.
Lipid layer thickness is marketed as a measure to help decide whether to proceed with LipiFlow (designed to treat meibomian gland dysfunction), with the idea that a thin central lipid thickness is “bad” and a thick layer is “good.” But some clinicians have found that central lipid thickness is of limited value in diagnosis or predicting therapy.
Measuring tear osmolarity
This is “a very useful measure, but what you want to know is stability over time, given that the hallmark of dry eye is instability,” Dr. Galor said. Unfortunately, each test chip costs $15 and you can’t check osmolarity 3 times in a row in a single visit. One measure of tear osmolarity isn’t as useful—not because osmolarity is a bad metric, but because you don’t get a good enough picture of homeostasis.
Measuring inflammation
InflammaDry measures the inflammatory marker MMP-9. While the test is qualitative (>40 mg/mL is positive), Dr. Galor estimates the degree of inflammation by the intensity of the pink line in the test’s results window and grades it as faint (minimal), light pink (mild), pink (moderate), or fuchsia (severe inflammation). She considers a pink or fuchsia line an indication that inflammation is an important contributor to the disease process.
Measuring Tear Protein Changes
Tears from patients with early dry eye have a significant reduction in tear protein content as a whole, associated with a decrease in proteins with antibacterial and protective functions. A decrease in proteins with lipid binding properties and an increase in inflammatory-related proteins were also shown. Changes in the abundance of a panel of tear proteins with divergent functions was found to better diagnose early DE than did conventional clinical tests.
