Ge YJ, Ou YN, Qu Y, et al. - Through systematically searching PubMed, EMBASE, Scopus, and Web of Science from inception to January 2021, researchers sought to localize candidate retinal biomarkers in Alzheimer disease (AD), mild cognitive impairment (MCI), and preclinical AD. There were 126 articles eligible for inclusion out of the 19,727 citations found. The thickness of the peripapillary retinal nerve fiber layer (pRNFL), total macular, and subfoveal choroid were significantly reduced in AD patients compared with healthy controls. In addition, patients with MCI had lower thickness of pRNFL, total macular, and subfoveal choroid compared with healthy controls. Optic nerve head morphology, retinal amyloid deposition, microvascular morphology and densities, blood flow, and electrophysiological markers were among the other candidate biomarkers. According to this systematic review and meta-analysis, retinal structural, vascular, and electrophysiological biomarkers have enormous potential for use in the diagnosis, prognosis, and risk assessment of AD and MCI.