METHODS: A cross-sectional study was conducted among type 2 DM patients. The patients were divided into three groups: no DR, non-proliferative DR (NPDR) and proliferative DR (PDR). Tears samples were collected using Schirmer strips for measurement of catalase, GPx and MDA.
RESULTS: A total of 171 patients were recruited in this study (no DR, 58 patients; NPDR, 57 patients; PDR, 56 patients). There was significant difference in the mean level of GPx in tears between the three groups (no DR, 658.08 ± 115.70 U/L; NPDR, 653.78 ± 87.90 U/L; PDR, 605.31 ± 107.47 U/L, respectively) before and after adjustment for covariates (p = 0.013 and p = 0.001, respectively). Bonferroni post-hoc analysis showed PDR group had significantly lower mean GPx level than in no DR (p=0.001) and NPDR (p=0.037) after adjustment for covariates. There was no significant difference of mean catalase and MDA in the tears between the three groups before and after adjustment for covariates.
CONCLUSION: This study demonstrated that diabetic patient with DR is associated with low level of GPx in tears, suggesting that this antioxidant enzyme is a potential biomarker for predicting the presence of DR.