Tear fluid plasmin activity of dry eye patients with Sjögren's syndrome

Thirty-two eyes of 16 patients with verified Sjögren's syndrome were examined for clinical signs of dry eye. Tear fluid samples were collected for plasmin assay. Ophthalmologic examinations included estimation of conjunctival or corneal discharge, filament formation and presence of conjunctival or corneal epithelial defects, assessment of tear meniscus height and measurement of tear fluid break-up time, Schirmer test, and fluorescein and Rose-Bengal staining graded by the van Bijsterveld score. Tear fluid plasmin activity (IU/l) was determined by a fluorometric assay and tear fluid flow (microl/min) was measured for calculation of tear fluid plasmin activity release (microIU/min). All patients had relatively dry eyes; the mean Schirmer test value was 5.7 +/- 0.5 mm/5 min. The mean tear fluid break-up time was also low, 7.7 +/- 0.5 s. The mean Bijsterveld score value was 2.5 +/- 0.5. Because collection of tear fluid by microcapillaries for the plasmin assay was difficult due to the low tear fluid flow rate, it was necessary to drop 20 microl of balanced salt solution topically on the cornea to aspirate a tear fluid sample. Despite this, the mean tear fluid plasmin activity was higher than in control individuals (7.75 +/- 1.51 IU/l vs. 0.73, range 0.64-0.80 IU/l). On the basis of these findings we conclude that elevated tear fluid proteolytic activity may play a role in the pathology of dry eye/ocular surface disease.