RESUMO
<p><b>OBJECTIVE</b>To investigate the dynamic changes of matrix metalloproteinase-9 (MMP-9) level in tear fluid within 12 months after laser in situ keratomileusis (LASIK).</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>