Changes in Tear Osmolarity and Matrix Metalloproteinase-9 Relative to Ocular Discomfort after Femtosecond Laser-Assisted Cataract Surgery

The aim of this study was to evaluate the changes in tear osmolarity and matrix metalloproteinase-9 (MMP-9) and their relationships with ocular discomfort in patients after femtosecond laser-assisted cataract surgery (FLACS). This retrospective observational case series reviewed medical records of 51 eyes of 51 patients who underwent FLACS. Tear osmolarity and MMP-9 were evaluated preoperatively and at 1 day, 1 week, and 1 month postoperatively. Tear osmolarity >= 310 mOsm/L and MMP-9 >= trace positive were defined as abnormal results. The ocular surface disease index (OSDI) was evaluated preoperatively and postoperatively at 1 month. Tear osmolarity level and the number of eyes with abnormal tear osmolarity results did not change significantly up to 1 month after surgery. MMP-9 level and the number of eyes with abnormal MMP-9 results increased at 1-day postoperatively and then decreased at 1-month postoperatively (all p < 0.001). Among the OSDI subscales, ocular discomfort was aggravated (p < 0.001) but the visual function score improved at 1 month postoperatively (p < 0.001). Ocular discomfort aggravated after FLACS without an increase in either tear osmolarity or MMP-9. Ocular discomfort which patients commonly experience after FLACS may be due to etiology other than development or aggravation of dry eye disease.