Evaluation of point-of-care test for elevated tear matrix metalloproteinase 9 in post-LASIK dry eyes

Aim To evaluate the performance of a point-of-care test for detection of matrix metalloproteinase 9 (MMP-9) levels in post-laser-assisted in situ keratomileusis (LASIK) dry eyes. Methods A comparative study between patients with mild to moderate post-LASIK dry eyes and age-matched normal subjects was conducted. Ocular surface disease index (OSDI), tear break-up time (TBUT), and tear film MMP-9 and total protein levels were compared between the two groups. A point-of-care test device (RPS InflammaDry, Sarasota, Florida, USA) was utilised to confirm elevated MMP-9 levels in tear film. Results Fourteen post-LASIK dry eyes and 34 normal eyes were included. There was no significant difference in age and gender between both groups (p>0.175). The OSDI was significantly higher (25.57.7 vs 7.4 +/- 2.5; p<0.001) and TBUT levels were significantly lower (5.4 +/- 0.9 vs 13.5 +/- 2.3; p<0.001) in patients with dry eye compared with normal subjects. The tear film MMP-9 levels were 52.7 +/- 32.5ng/mL in dry eyes and 4.1 +/- 2.1ng/mL in normal eyes (p<0.001). MMP-9 levels were >40ng/mL in 7/14 (50.0%) post-LASIK dry eyes. The InflammaDry was positive in 8/14 (57.1%) post-LASIK eyes. All positive cases had tear film MMP-9 levels 38.03ng/mL. Agreement between InflammaDry and MMP-9 was excellent with Cohen value of 0.857 in post-LASIK dry eyes. Conclusions Only half of post-LASIK dry eyes were found to have significant inflammation associated with elevated MMP-9. The OSDI is useful to non-specifically identify patients with symptomatic dry eye while the InflammaDry determined which patients with dry eye were associated with significant inflammation that may guide therapeutic management decisions.