Differential methylation in rare ophthalmic disorders: a systematic review protocol.

backgroundRare ophthalmic conditions often cause degenerative vision loss which leads to loss of independence, ability to work and ultimately quality life. Differential methylation is an epigenomic marker that is a feature of several diseases, including eye conditions. This review will aim to elucidate the extent to which differential methylation has been identified in rare ophthalmic conditions.

methodsA systematic review will be conducted of articles found in the electronic databases MEDLINE, EMBASE, PubMed and Cochrane Library of Systematic Reviews. Grey literature databases GreyLit and OpenGrey will be searched for relevant unpublished sources. Reference lists of articles which meet eligibility criteria will also be screened for forward and reverse citations. Eligibility criteria will include quantitative articles published, before July 2018, written in English and featuring analysis of differential methylation in rare ophthalmic disorders. Studies will be screened firstly by title, abstract and keywords and then by full text for any remaining sources, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data extraction of key characteristics will be completed using customised forms. Methodological rigour will be assessed using customised forms modelled on the Joanna Briggs Institute critical appraisal forms. DISCUSSION: This systematic review will enable us to identify if differential methylation can be used to characterise rare ophthalmic disease, which could have crucial implications for improving the accuracy and speed of diagnosis, identifying novel therapeutic targets to reduce or prevent vision loss and overall improving understanding of rare ophthalmic disease. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018094231.