Abstract: Objective To investigate the dynamic changes of matrix metalloproteinase-9 (MMP-9) level in tear fluid within 12
months after laser in situ keratomileusis (LASIK). Methods Twenty-two myopic patients undergoing uneventful LASIK were
enrolled in this study. Tear fluid samples were collected from the patients for measurements of MMP-9 level using Western
blotting preoperatively, at 7 and 14 days, and at 1, 2, 3, 6, and 12 months after the surgery. Results MMP-9 concentrations in
the tear fluid of post-LASIK patients showed a time-dependent variation pattern. MMP-9 reached its peak level in the tear
fluid at 14 days postoperatively, which was 2.70 times the preoperative level; it gradually decreased thereafter but was still 1.38
times the preoperative level at 12 months after the surgery. Conclusions MMP-9 concentrations in the tear fluid of post-LASIK
patients show a time-dependent variation pattern and remains higher than the preoperative level even at 12 months after the
surgery, suggesting that corneal wound healing after LASIK lasts for more than 12 months.