The effect of diabetes on corneal endothelium: a meta-analysis

Background: This research was conducted with the aim to determine the effect of diabetes mellitus on corneal endothelial cells. Methods: The terms: (diabetes mellitus or diabetes or diabetic) and (corneal endothelium or cornea or Corneas) searched in Pubmed, Embase, Cochrane, and Web of science until August 2019. The included types of studies contained observational studies. The standard mean difference (SMD) which was deemed as main size effects for continuous data was calculated by means and standard deviations. The data on corneal endothelial cell density (ECD), mean cell area (MCA), cell area variation coefficient (CV) and percentage of hexagonal cells (HEX) included in the study were collected and analyzed using stata15.1. Results: The final 16 cross-sectional studies and 2 case-control studies were included for the meta-analysis. Meta-analysis revealed that diabetes mellitus could reduce ECD (SMD = - 0.352, 95% CI -0.538, - 0.166) and the HEX (SMD = - 0.145, 95% CI -0.217, - 0.074), in addition to increasing CV (SMD = 0.195, 95% CI 0.123, 0.268). Nevertheless, there was no statistically significant differences observed when combining MCA (SMD = 0.078, 95% CI -0.022, 0.178). In subgroup analysis, Type 2 diabetes patients owned less corneal ECD (P < 0.05). Moreover the same results also found during the subgroup form Asia, Europe and American. The meta-regression revealed the type of diabetes mellitus might be contributing to heterogeneity. (P = 0.008). The results indicated a significant publication bias for studies, with combined CV (Begg's test, P = 0.006; Egger's test, P = 0.005) and merged combined HEX (Begg's test, P = 0.113; Egger's test, P = 0.024). Conclusions: As indicated by meta-analysis, diabetes mellitus could cause a detrimental effect on corneal endothelium health. Diabetes mellitus contributed to the instability of corneal endothelium during the analysis. Therefore, further research is considered necessary to confirm our research results.

Automated summary

The research revealed that diabetes mellitus has a negative impact on corneal endothelial cells, leading to a decrease in cell density and hexagonal percentage, as well as an increase in cell area variation coefficient. There were no significant differences in the mean cell area. Type 2 diabetes patients showed a lower corneal endothelial cell density compared to other groups. Additionally, publication bias was observed in the studies, especially in terms of combined variance and hexagonal cell percentage.