Comparison of tear index and tear film function between type 2 diabetic patients and normal subjects

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Objective To compare the tear related indexes of patients with type-2 diabetes and the healthy subjects, analyze the functions of tear film of these two groups and provide significant theoretical evidences for the causes of the increased prevalence of dry eye in patients with type-2 diabetes and their pathogenesis. Methods A case-control study was designed.During the epidemiological investigation of dry eye in communities, 79 patients with diabetes and 74 normal healthy subjects were randomly selected as participants in this case-contol study.Dry eye tests including tear film break-up time (BUT), SchirmerⅠtest (SⅠt) and corneal fluorescein staining were performed.The tears were collected to detect mucoprotein-5AC (MUC-5AC), matrix metalloproteinase 9 (MMP-9), receptor of advanced glycation endproducts (RAGEs) and the content of insulin.The diagnosis standard referred to Experts Consensus on Clinical Diagnosis and Treatment of Dry Eye published in 2013.The study was followed the Declaration of Helsinki.This study protocol was approved by Medical Ethics Committee of the Shanghai General Hospital, Shanghai Jiaotong University(No.2016KY005), and written informed consent was obtained from all subjects. Results There were significant differences between 79 diabetes patients and 74 normal healthy subjects in the value of BUT, SⅠt and corneal fluorescein staining (all at P<0.05). The value of BUT and SⅠt in patients with diabetes were lower than those in the control group, while the corneal fluorescein staining scores of patients were higher than those of normal healthy subjects, with significant differences (P<0.05). In addition, compared with normal healthy subjects, the diabetic patients were higher in the value of MMP-9 and RAGEs, but lower in the content of insulin and MUC-5AC, with significant differences (P<0.05). There were significant differences in gender, diabetes duration, MMP-9, and MUC-5AC between the dry and non-dry eyes in the diabetic group (P<0.05). Women were more likely to develop dry eyes with a significant difference (t=4.35, P=0.04). The duration of diabetes in dry eye group was higher than that in non-dry eye group, with a significant difference (t=2.56, P=0.01); the value of MMP-9 in dry eye group was (1 052.37±157.68)pg/ml, which was significantly higher than that in non-dry eye group ([459.11±258.67]pg/ml)(t=11.92, P<0.01); the value of MUC-5AC in dry eye group was (867.83±121.82)pg/ml, which was significantly lower than in non-dry eye group ([972.93±153.52] pg/ml)(t=-3.30, P<0.01). There was no statistical difference in age and insulin between the two groups.Pearson correlation analysis showed that MMP-9 was negatively correlated with BUT (r=-0.349, P<0.01), and positively correlated with corneal fluorescein staining (r=0.181, P=0.026). MUC-5AC was positively correlated with SⅠt (r=0.367, P<0.01). Conclusions Dry eye prevalence is significantly related with the decrease in MUC-5AC and the increase in MMP-9 in community-based diabetic patients. Key words: Diabetes mellitus; Tear index detection; Tear film function; Dry eye