Obstructive Sleep Apnea and Keratoconus: A Systematic Review and Meta-analysis.

BACKGROUND: Despite the increasing number of studies focused on the association between obstructive sleep apnea (OSA) and keratoconus (KC), to date, no comprehensive meta-analysis or systematic review was published. OBJECTIVE: The objective of this study was to evaluate the association between OSA and KC. DATA SOURCES: Sources of data were PubMed, Scopus, and Web of Science databases. STUDY ELIGIBILITY CRITERIA: The criteria for study eligibility were case-control studies and cohort studies reporting data on the association of OSA with KC with risk ratio, odds ratio, or hazard ratio with 95% confidence intervals or sufficient raw data for calculation. STUDY APPRAISAL AND SYNTHESIS METHODS: Meta-analysis was conducted with a random-effects model using odds ratio with 95% confidence interval as the effect size. Heterogeneity was evaluated using the Q and I tests. Sensitivity analysis and assessment of publication bias were performed. RESULTS: Five studies (four case-control studies and one cohort study) published between 2012 and 2016 and involving 33,844 subjects (16,922 patients with KC, 16,922 controls) were included in this meta-analysis. A significant association between OSA and KC has been shown (pooled odds ratio, 1.841; 95% confidence interval, 1.163 to 2.914; P = .009). A significant heterogeneity was observed (Q = 15.8, I = 74.6%). There was no evidence of significant publication bias (P = .07). The sensitivity analyses indicated the stability of results. LIMITATIONS: Heterogeneity across the studies was observed. Data from four hospital-based case-control studies and one large population-based cohort study were combined. Most of the included studies ascertained OSA by the Berlin Questionnaire, which is a screening tool. CONCLUSIONS: This meta-analysis provides significant evidence that OSA is associated with KC. Therefore, a proper screening for OSA is warned for KC patients for the prevention of various cardiovascular comorbidities. Further prospective studies are warranted to explore more in-depth the casual relationship between the two conditions.