The utility of normal tear osmolarity results
Rule out dry eye, rule in the real diagnosis
The whole picture
In our study, my colleagues and I concluded symptoms are not the best feature by which to diagnose DED. They overlap too frequently with other anterior segment pathologies for this to be an accurate approach. Measuring tear osmolarity is a simple way to rule out DED so we can look for an alternate diagnosis.
In addition to tear osmolarity, other point-of-care diagnostics contribute to building a complete picture of DED severity and its subtypes, as well as to helping to rule in alternate ocular surface diagnoses. These include tear MMP-9 (InflammaDry, RPS), meibography and lipid layer thickness (LipiView, TearScience), tear IgE and lactoferrin (TearScan, Advanced Tear Diagnostics), and others.
We are now learning more about how to evaluate these tests by themselves and in combination as a basket of data. What if a patient with dry eye symptoms has normal osmolarity and a negative MMP-9 test, or normal osmolarity and elevated MMP-9?
At first glance, this might seem to add diagnostic complexity, but if you have faith in the results and follow a comprehensive diagnostic algorithm incorporating all the testing combinations, you will save time by knowing when to pause and look for alternative diagnoses.
1. The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007). Ocul Surf. 2007 Apr;5(2):75-92. PMID: 17508116
2. Brissette AR, Bohm KJ, Starr CE. The utility of a normal tear osmolarity test in symptomatic patients. Poster presented at: The 8th International Conference on the Tear Film & Ocular Surface: Basic Science and Clinical Relevance; 2016 Sept 7-10; Montpellier, France.