Traditionally, Schirmer’s Test and Tear Break Up Test – have been the standard dry eye measures. More recently, new devices and instruments have been introduced to test for tear parameters that are indicative of dry eyes. Knowing how dry your eyes are can help gauge your recovery, providing an objective measurement rather than subjective.
Two devices that are commonly used to conduct objective dry eye testing in many eye doctor’s offices:
1. Tear Lab Osmolarity System (TearLab, San Diego, CA) – measures the osmolarity of a 50-nL tear sample.
2. InflammaDry, Rapid Pathogen Screening test (Rapid Pathogen Screening, Inc, Sarasota, FL). This is a new device which uses a disposable single-use assay that analyzes the matrix metalloproteinase 9 (MMP-9) qualitatively in tears. MMP-9 is considered to be a marker for inflammation, usually associated with dry eye. Enzyme-linked immunosorbent assay [ELISA] test was also used to determine and confirm the concentrations of MMP-9 in tears collected via Schirmer strips.
This research focuses on a study to evaluate the MMP-9 in tears and tear film osmolarity in a group of elderly patients (n=20; age = 72.0±6.1yrs) with previously un-diagnosed dry eye. Dry eye symptoms (Ocular Surface Disease Index questionnaire) and signs (tear break-up time, Schirmer test, ocular surface staining) were also evaluated in these patients.
Patients were classified into four groups: symptoms (classification A: OSDI ≥10), suspected mild dry eye (classification B), osmolarity difference > 8 mOsm/L between both eyes (classification C), and osmolarity cutoff at 308 mOsm/L (classification D: >308 mOsm/L).
Eleven percent (11%) of the symptomatic group and 14% of the suspected mild dry eye were positive for MMP-9. ELISA tests confirmed that the InflammaDry MMP-9 tests were accurate. Sixty-seven percent (67%) of the symptomatic and 64% of the suspected mild dry eye were positive for tear osmolarity.
Tear film osmolarity showed a trend toward correlation with symptoms, whereas the quantitative MMP-9 values showed a trend toward correlation with corneal staining. The research concludes that MMP-9 is possibly a late-stage sign that is hardly overexpressed in mild dry eye, whereas tear osmolarity tends to be a more frequent early indicator of ocular surface instability within mild dry eye patients. A limitation of this study is the small sample size.
Abstract is from –
1. Schargus M, Ivanova S, Kakkassery V, Dick HB, Joachim S. Correlation of Tear Film Osmolarity and 2 Different MMP-9 Tests with Common Dry Eye Tests in a Cohort of Non-Dry Eye Patients. Cornea. Apr 23 2015.