Tilt and decentration of an intraocular lens (IOL) within the capsular bag may induce higher-order aberrations, glare, reduced contrast sensitivity, and monocular diplopia; presbyopia-correcting and toric IOL are particularly sensitive to misalignment. Accurately evaluating the spatial positions of the natural crystalline lens before surgery and IOL after surgery is of great significance for the selection of functional IOL, the formulation of surgical plans, and the interpretation of postoperative visual quality. CASIA2 combines swept-source optical coherence tomography (OCT) with anterior segment three-dimensional reconstruction technology, enabling simultaneous identification of the anterior and posterior surfaces of the cornea, iris, lens, or IOL, and calculating the tilt, decentration, and orientation using built-in algorithms. CASIA2 swept-source anterior segment OCT uses the corneal topographic axis as a reference and enables three-dimensional quantification of crystalline lens and IOL position without pharmacologic dilation. The relationship between preoperative crystalline lens position and postoperative IOL position, as well as the value of combining preoperative CASIA2 measurements with ocular biometry for risk stratification of postoperative IOL malposition and individualized IOL selection, remains unclear. The clinical relevance of IOL tilt and decentration, the measurement principles and technical advantages of CASIA2, the positional characteristics of the crystalline lens and postoperative IOL, and associated factors including ocular biometry, high myopia, previous vitrectomy, and IOL design were summarized. The predictive value of preoperative crystalline lens position was also discussed.