Role of optical coherence tomography in depression detection: a protocol of systematic review and meta-analysis

IntroductionOptical coherence tomography (OCT) is a non-invasive approach for detecting changes in the retinal layers, which may also reflect changes in brain structure and function. As one of the leading causes of disability worldwide, depression has been associated with alteration of brain neuroplasticity. However, the role of OCT measurements in detecting depression remains unknown. This study aims to employ a systematic review and meta-analysis approach to explore ocular biomarkers measured by OCT for detecting depression. Methods and analysisWe will search studies describing the relationship between OCT and depression across seven electronic databases, and retrieve articles published from database inception to date. We will also manually search grey literature and reference lists included in the retrieved studies. Two independent reviewers will screen studies, extract data and assess risk of bias. Target outcomes will include peripapillary retinal nerve fibre layer thickness, macular ganglion cell complex thickness and macular volume, as well as other related indicators. Next, we will conduct subgroup analysis and meta-regression to explore study heterogeneity, then perform sensitivity analysis to investigate the robustness of the synthesised results. Meta-analysis will be performed using Review Manager (V.5.4.1) and STATA (V.12.0), and the certainty of evidence will be graded according to the Grading of Recommendations Assessment, Development and Evaluation system. Ethics and disseminationEthics approval is not necessary because the data used in this systematic review and meta-analysis will be extracted from published studies. Study results will be disseminated by publishing our findings in a peer-reviewed journal.