We artificially divide cataracts into four stages: the incipient, immature, mature and overripe stages. In the incipient stage, the clouding of the lens is not easily detected because it is often in the peripheral part and does not affect vision much, and is only detected during dilated pupil examination. In the immature stage, special attention should be paid to patients with underlying factors of closed-angle glaucoma, as the swelling of the crystal causes an acute attack of glaucoma. In the mature and overripe stages, vision is severely reduced and life is often unmanageable, and in the overripe stage it can also cause some serious complications such as: lens protein allergic uveitis, lens lysis glaucoma and crystal pendulous ligament rupture. Therefore, it is not recommended that cataract patients must wait until their vision reaches the stage of complete invisibility, i.e., the mature stage or the overmaturity stage, before surgery is performed.