Myopia has become a critical global public health issue, driven by the increasing prevalence of pathological myopia, which poses significant risks to visual health and leads to potential economic productivity losses. The theory of peripheral defocus affecting the visual feedback mechanism in emmetropization may play a role in the prediction and management of myopia. However, progress has been hindered by challenges, including the ambiguous definition and classification of peripheral defocus, as well as inconsistencies in clinical research findings. This review offers a comprehensive examination of peripheral refraction, encompassing its definition, measurement methodologies, characteristics across different refractive states, clinical applications, and underlying mechanisms. Additionally, it addresses current research limitations, such as the need to differentiate between intrinsic and extrinsic peripheral defocus and the absence of high-resolution measurement tools suitable for large-scale clinical studies. By advancing the understanding of peripheral refraction, this review aims to inform future researchers and clinical practitioners, paving the way for more effective strategies to prevent and manage myopia in children.