title: Correlation of Tear Film Osmolarity and 2 Different MMP-9 Tests With Common Dry Eye Tests in a Cohort of Non-Dry Eye Patients.
abstract: OBJECTIVE
  Given that early-stage dry eye is difficult to diagnose, the purpose of this study was to evaluate the performance of matrix metalloproteinase 9 (MMP-9) and tear film osmolarity (TFO) in a cohort of elderly patients with potential dry eye disease (DED).
  
  
  METHODS
  A group of 20 patients, aged 60 years and above, previously undiagnosed with DED were selected. The following DED tests were performed: tear osmolarity, MMP-9 (InflammaDry), Schirmer test, tear film break-up time, Ocular Surface Disease Index (OSDI) questionnaire, corneal fluorescein staining, and conjunctival lissamine green staining. MMP-9 concentrations in tears collected through Schirmer strips were analyzed by an MMP-9 enzyme-linked immunosorbent assay [ELISA]. Subjects were classified by symptoms (classification A: OSDI ≥10, n = 9), based on suspected mild dry eye (classification B: n = 14), TFO difference >8 mOsm/L between both eyes (classification C: n = 13), and TFO cutoff at 308 mOsm/L (classification D: >308 mOsm/L, n = 11).
  
  
  RESULTS
  Eleven percent (1/9) of the symptomatic and 14% (2/14) of the suspected mild dry eye were positive for MMP-9. InflammaDry MMP-9 tests were confirmed to be accurate through an ELISA. Sixty-seven percent (6/9) of the symptomatic and 64% (9/14) of the suspected mild dry eye were positive for tear osmolarity. None of the evaluated tear film parameters showed a significant correlation, although tear osmolarity and symptoms trended toward significance (r = 0.433, P = 0.06), whereas MMP-9 and corneal staining showed a positive association (r = 0.376, P = 0.10).
  
  
  CONCLUSIONS
  Similar to corneal staining, the MMP-9 is likely a late-stage sign that is rarely overexpressed in mild subjects, whereas tear osmolarity tends to be a more frequent early indicator of ocular surface disequilibrium within mild subjects.
authors.affiliation: *Department of Ophthalmology, Ruhr-University Hospital, Bochum, Germany; and †Experimental Eye Research Institute, Ruhr-University Eye Hospital, Bochum, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Schargus
authors.forename: Svetlana
authors.initials: S
authors.lastname: Ivanova
authors.forename: Vinodh
authors.initials: V
authors.lastname: Kakkassery
authors.forename: H Burkhard
authors.initials: HB
authors.lastname: Dick
authors.forename: Stephanie
authors.initials: S
authors.lastname: Joachim
mesh_terms: D000368:Aged; D015352:Dry Eye Syndromes / Q000175:diagnosis* / Q000201:enzymology; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D009994:Osmolar Concentration; D013194:Staining and Labeling; D011795:Surveys and Questionnaires; D013666:Tears / Q000737:chemistry* / Q000201:enzymology*
chemical_list: D005136:Eye Proteins; C042434:tear proteins; D020780:Matrix Metalloproteinase 9