Cataract surgery techniques and IOL implantation have evolved very significantly over the past few years. Although most patients with monofocal IOLs have been able to achieve excellent vision, they still need glasses for near vision. Implantation of multifocal IOLs can solve this problem to some extent. Multifocal IOLs are revolutionarily designed to create a series of almost spaceless focal points in the eye, which can improve near vision without significant adverse effects on distance vision, thus significantly reducing the dependence of patients on glasses after cataract surgery. First of all, we need to understand the working mechanism of multifocal IOLs. A prerequisite for proper IOL implantation is an understanding of its design concept and function. Let’s take the AcrySof ReSTOR multifocal IOL as an example. It is a progressive diffraction type multifocal IOL, an IOL for presbyopia, and this step progressive diffraction optical surface is designed to progressively fuse the diffraction area with the refraction area, making it easier for the eye to adapt to the transition between focal points at different distances, which can reduce visual interference and improve imaging quality. The central 3.6mm of the optical section is a stepped progressive diffraction area that produces an additional +4.00D, equivalent to an additional +3.20D in the plane of the eyeglasses, and this design allows the optimal near point to be located approximately 31cm in front of the patient’s eyes. As the light passes through the center of the IOL’s optical section, the diffraction stripe produces light waves that focus to form both the near and far focal points. The retina receives both near and far images simultaneously, and the brain then decides which one to accept. Surrounding the diffractive region is a refractive region that produces a far focus. In dim light environments, when the pupil is dilated, there is more light converging on the far focus, thus effectively reducing visual interference.