Microglial activation is one of the main pathogenic factors to cause retinal neuroinflammation. Recently, with the advancement of retinal imaging technologies, hyperreflective foci(HRF), as a novel biomarker in optical coherence tomography(OCT)imaging, have received more attention in retinal neuroinflammation. Current research demonstrated that HRF are the aggregates mainly derived from the activated microglia in retina or mononuclear phagocyte-macrophage from the blood. HRF were defined as

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... rete and well-circumscribed hyperreflective dot-shaped lesions with the maximum diameter between 20-50μm in retina and choroid imaged with OCT. Under pathological conditions, the number of HRF increases significantly. Under pathological condations, the number of HRF was obviously increased, which might be related to the severity of some retinal diseases. However, the research on the source and function of HRF is still in its infancy. This review is aimed to describe the basic characteristics of HRF and their roles in both retinal inflammatory diseases and neurodegenerative diseases of the central nervous system. HRF are expected to be a potential and novel biomarker of inflammation for early diagnosis and prognosis of neuroinflammation in both retinal and central nervous system diseases.