Why do they vary? During cataract surgery, IOLs are implanted to correct the aphakic state after removal of the lens. Therefore, each surgeon should be aware of the optical role of the implanted IOL before implanting it. Otherwise, the IOL implantation may lead to a high degree of refractive error, thus defeating the purpose of the IOL implantation. For this reason, the calculation and selection of the IOL degree before the surgery becomes crucial, and through accurate biological measurement before the surgery and combined with the actual work and life needs of the patient, the appropriate degree of IOL can be selected so that the refractive state desired by the patient before the surgery can be achieved or approached after the surgery, and even the original refractive state before the surgery can be corrected by the IOL. According to the functional classification 1.Adjustable IOL: With the improvement of cataract surgery and the increase of people’s demand for high quality functional vision, improving the adjustment function of the post-cataract surgery eye has become a hot spot and a trend of current research. Physiologically based accommodation refers to the ability of the eye to clearly image objects at any distance in the retina by the contraction of the ciliary muscle. The design of AIOL adopts the principles of displacement adjustment and deformation adjustment, which are similar to the adjustment of human lens. The Tetraflex (Foley) adjustable IOL from Lenstec of the U.S., which is widely used in China, is a closed 5-degree four-touch loop that uses ciliary muscle contraction and vitreous body movement to accept different capsular bag size forces, resulting in an arch shape on the side of the lens and a certain deformation of the optical part to complete adjustment. In addition, good biocompatibility, no halo or glare, and pusher implantation are also advantages that this lens has. 2.Aspheric IOL: Aspheric IOL has the effect of reducing postoperative spherical aberration, which theoretically can bring better visual quality and visual function, thus gaining more and more attention. Different design concepts of aspheric IOLs are emerging. By implanting aspheric IOLs, relatively better contrast sensitivity can be obtained, avoiding the occurrence of adverse phenomena such as postoperative glare, halos and night vision loss, making the IOL eye closer to the physiological state and bringing better visual quality to patients. Among them, SOFTEC HD zero spherical aberration aspheric IOL, which is certified by FDA, is the most accurate aspheric IOL with a minimum increment of 0.25D. Not only that, its zero spherical aberration design is more universally applicable to the population and will not change the original aberration. 3.Multifocal IOLs: Multifocal IOLs are divided into refractive and diffractive types. The concept of refractive type is relatively simple, mostly biconvex lens, with 3-5 refractive areas of different diopters on the front surface, different areas are responsible for distant focus or near focus imaging, the imaging depends on the pupil size, and the imaging quality is greatly affected by the pupil size and artificial lens deviation. Such crystals are represented by AMO’s ReZoom. The diffractive type of optical surface adopts a stepped progressive diffraction technique, presenting a stepped design in 12 concentric circles with a height between 0.3-1.2 microns and a decreasing step width with the same regularity, while the peripheral area is the refractive zone. The stepped progressive diffraction structure blends with the peripheral refractive zone, making the distribution of light energy gradually favor the distant focus as the pupil increases. As a result of the redistribution of light energy, a decrease in visual quality and the occurrence of visual disturbances (glare, halos) are inevitable. A representative of this type of crystal is Alcon’s ReSTOR.