Heritability of glaucoma and glaucoma-related endophenotypes: systematic review and meta-analysis protocol

INTRODUCTION: Glaucoma is the second leading cause of age-related vision loss worldwide; it is an umbrella term that is used to describe a set of complex ocular disorders with a multifactorial aetiology. Both genetic and lifestyle risk factors for glaucoma are well established. Thus far, however, systematic reviews on the heritability of glaucoma have focused on the heritability of primary open-angle glaucoma only. No systematic review has comprehensively reviewed or meta-analysed the heritability of other types of glaucoma, including glaucoma-related endophenotypes. The aim of this study will be to identify relevant scientific literature regarding the heritability of both glaucoma and related endophenotypes and summarise the evidence by performing a systematic review and meta-analysis. METHODS AND ANALYSIS: This systematic review will follow the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols 2015 checklist, which provides a standardised approach for carrying out systematic reviews. To capture as much literature as possible, a comprehensive step-by-step systematic search will be undertaken in MEDLINE (PubMed), EMBASE, Web of Science and ScienceDirect, and studies published until 31 December 2017 will be included. Two reviewers will independently search the articles for eligibility according to predefined selection criteria. A database will be used for screening of eligible articles. The quality of the included studies will be rated independently by two reviewers, using the National Health Institute Quality Assessment tool for Observational Cohort and Cross-Sectional Studies. A random-effects model will be used for the meta-analysis. This systematic review is registered with the International Prospective Register of Systematic Reviews with a registration number: CRD42017064504. ETHICS AND DISSEMINATION: We will use secondary data from peer-reviewed published articles, and hence there is no requirement for ethics approval. The results of this systematic review will be disseminated through publication in a peer-reviewed scientific journal.