Abstract
The tear matrix metalloproteinase-9 (MMP-9) immunoassay (Inflammadry) exhibits variable results in dry eye (DE) patients. We investigated if the tear volume in DE patients affects the results of MMP-9 immunoassay in clinical and in vitro settings. This cross-sectional study enrolled 188 eyes of 188 DE patients. The clinical symptoms and signs of DE were assessed using the Ocular Surface Disease Index and visual analog scale, strip meniscometry, tear break-up time, and tear meniscus height (TMH), area (TMA), and depth (TMD) using swept-source optical coherence tomography and corneal and conjunctival staining scores. For quantitative evaluation, the bands produced by the InflammaDry test were analyzed with ImageJ. DE subjects were grouped according to MMP-9 positivity and TMH. The InflammaDry-positive group showed greater TMH, TMA, and TMD than the MMP-9-negative group (p < 0.05). InflammaDry test band density in the high TMH group was significantly greater than that in the low and normal TMH groups (p < 0.05). InflammaDry test band density correlated positively with TMH, TMA, and TMD (all p < 0.05). InflammaDry test results were influenced by tear volume. Low tear volume in aqueous tear-deficient DE may induce false-negative results, and reflex tearing during the test may induce false-positive results.
Highlights
Dry eye (DE) is a multifactorial disease caused by changes in the quality and/or quantity of the precorneal tear film [1]
Current diagnosis of DE is based on a combination of clinical signs, such as those determined by the Schirmer test, tear break-up time, and staining scores, as well as symptoms, which are determined by formalized questionnaires
Positive matrix metalloproteinase-9 (MMP-9) tests were confirmed in 120 patients, and negative results were noted in 68 patients
Summary
Dry eye (DE) is a multifactorial disease caused by changes in the quality and/or quantity of the precorneal tear film [1]. Current diagnosis of DE is based on a combination of clinical signs, such as those determined by the Schirmer test, tear break-up time (tBUT), and staining scores, as well as symptoms, which are determined by formalized questionnaires. The Schirmer test results, tBUT, and corneal staining scores have long been used as the main indicators of DE, these tests lack objectivity and show low reproducibility due to user-dependent errors [2,3]. Efforts are being made to develop new objective methods for DE diagnosis, such as tear osmolarity tests and the tear matrix metalloproteinase (MMP)-9 immunoassay [4,5].
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