The defocus curve, which quantifies visual performance under various defocus states to accurately evaluate the eye's ability to achieve clear vision across a continuous range of distances, is a vital tool for assessing visual quality. With the aging population and improved quality of life driving a significant increase in the demand for presbyopia correction, the application of the defocus curve has continually expanded in ophthalmic clinical practice, particularly in the perioperative period of presbyopia-correcting corneal refractive surgery and refractive cataract surgery, where it aids in personalized surgical planning and proves valuable for patient education and postoperative visual quality assessment. This article systematically reviews the examination methodology, influencing factors, analytical approaches, and recent clinical advancements of defocus curves, focusing on the potential impact of variables such as pupil diameter, contrast sensitivity, and chart selection on results; it further discusses current limitations including lack of standardization and insufficient assessment of dynamic visual performance, and proposes future research directions based on the latest literature. The aim is to provide valuable insights for researchers and clinicians, promote the standardized and normative application of defocus curves, and ultimately enhance the overall efficacy of presbyopia correction and patients' quality of visual life.