Indexed on: 25 Apr '15Published on: 25 Apr '15Published in: Cornea
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).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).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).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.