Tear Levels of Inflammatory Cytokines in Keratoconus: A Meta‐Analysis of Case‐Control and Cross‐Sectional Studies
Huan Zhang, Xiupeng Cao, Ying Liu, Peihong Wang, Xuan Li
Abstract
Purpose . To assess the tear levels of inflammatory cytokines in patients with keratoconus (KC). Design . Systemic review and meta‐analysis. Methods . The following electronic databases and search engine were searched: PubMed, EMBASE, Web of Science, and Google Scholar. A systematic search of all relevant studies published through January 2021 was conducted, and the standardized mean difference (SMD) and 95% confidence interval (CI) of cytokine levels were calculated to estimate the pooled effects. Sensitivity analysis, subgroup analysis, and metaregression were applied to explore the sources of heterogeneity. Results . A total of 7 studies with 374 participants (374 eyes) from clinical studies were included. The tear levels of interleukin‐1 beta (IL‐1 β ), interleukin‐6 (IL‐6), and tumor necrosis factor alpha (TNF‐ α ) were significantly increased in KC compared with normal controls. The SMD of IL‐1 β was 1.93 (95% CI 0.22 to 3.65, P = 0.03). The SMD of IL‐6 was 1.22 (95% CI 0.59 to 1.84, P < 0.001). The SMD of TNF‐ α was 1.75 (95% CI 0.66 to 2.83, P = 0.002). There was no significant difference between the two groups on interleukin‐4 (IL‐4) and interleukin‐10 (IL‐10). The SMD for IL‐4 was 2.36 (95% CI ‐0.28 to 5.00, P = 0.08) and for IL‐10 was 0.30 (95% CI ‐1.29 to 1.89, P = 0.71). Meta‐regression analysis indicated that the heterogeneity maybe significantly correlated with the method of detection, the different ages, and the source of population. Conclusions . Our meta‐analysis demonstrated that proinflammatory cytokines IL‐1 β , IL‐6, and TNF‐ α were increased, indicating that cytokine profile changed in KC tears and inflammation may play an important role in the pathogenesis and development of KC.