Meta-analysis and review on the changes of tear function and corneal sensitivity in diabetic patients

To perform a comprehensive evaluation and comparison of tear function in diabetic and non-diabetic patients. Research related to tear function in diabetic and non-diabetic patients was gathered using PubMed, EBSCO, OVID. Two reviewers independently conducted the literature search. The quality assessment and the data extraction were performed in accordance with exclusion criteria and cross-checking. RevMan 5.1.7 software was used for the meta-analysis. The tear film break-up time was studied in eight articles with a total of 1449 samples. Through a random-effects model analysis, the combined weighted mean difference (WMD) was -4.44 [-5.87, -3.01]. The time in diabetic patients was shorter than that in the non-diabetic group (p < 0.00001). The basal tear secretion test was studied in seven articles with a total of 949 samples. The combined WMD was -3.96 [-5.70, -2.23], and the difference between the diabetic group and control group was statistically significant (p < 0.00001). The total tear secretion test was studied in five articles with a total of 921 samples. The combined WMD was -3.96 [-7.43, -0.50]. The difference between the diabetic and control groups was statistically significant (p = 0.03). The corneal sensitivity was compared in eight studies with a total of 976 samples. Through a random-effects model analysis, the standardized mean difference (SMD) was -5.14 [-6.99, -3.29]. The corneal sensitivity was lower in diabetic patients than the control group (p < 0.00001). Our study suggests that the tear functions are worse in diabetic patients compared with the control group. Moreover, patients with PDR are more predisposed to impaired tear functions.