Under normal circumstances, the lens is suspended on the ciliary body by the suspensory ligament, and its center is almost consistent with the visual axis. Due to congenital, traumatic or pathological reasons, the suspensory ligament of the lens is partially or completely defective or disconnected, causing imbalance or loss of the suspension force on the lens, which may cause the lens to leave its normal physiological position, which is called ectopia lentis. According to the degree of suspensory ligament defect or disconnection (partial or complete), ectopia lentis is divided into subluxation and luxation/dislocation; according to the cause, ectopia lentis is divided into congenital, spontaneous and traumatic.