Allergic rhinitis and keratoconus: a systematic review and meta-analysis

Background The relationship between keratoconus and various allergic diseases has been a subject of controversy. Objective In the present study, a systematic review and meta-analysis was conducted to investigate the association between allergic rhinitis (AR) and keratoconus. Methods Relevant and eligible studies from PubMed, Web of Science, and Cochrane Library were systematically reviewed to evaluate the association between AR and keratoconus. Observational studies containing the number of patients with and without keratoconus and the number of patients with keratoconus diagnosed with or without AR were included. Two reviewers independently screened for eligible studies and extracted data from the included studies. A bivariate meta-analysis was conducted to compare the odds of keratoconus occurrence in patients with and without AR. The main outcome was the odds ratio of keratoconus occurrence in patients with AR. A sensitivity test was performed using the adjusted odds ratio reported in the included studies to validate the findings. Results Seven studies involving 775,574 participants were included in this meta-analysis. Among them, 29,082 patients had keratoconus. The pooled odds ratio of keratoconus occurrence in patients with AR was 1.71 (95% confidence interval [CI]: 1.36–2.15; P < 0.001; I2 = 96%), and the pooled adjusted odds ratio was 1.72 (95% CI: 1.23–2.40; P = 0.001; I2 = 97%). Conclusion Patients with AR showed significantly higher odds of keratoconus occurrence than those without AR. Future studies are warranted to investigate the causal relationship and evaluate the cost-effectiveness of early screening using methods such as corneal topography and referral for keratoconus in patients with AR.