MMP9 and glaucoma: In addition, our data provide the first quantification of tear MMP-9 in glaucoma patients, generally measured by semi-quantitative methods such as InflammaDry, which generates a positive result when tear the MMP-9 concentration is over 40 ng/mL [51,52], or by zymography, a technique that evaluates the activity of the collagenases in a sample [53].