An intraocular lens (IOL) is an artificial lens that is implanted in the eye to replace the natural lens during cataract surgery or refractive lens exchange. It is designed to restore clear vision by focusing light onto the retina, and can be made of various materials such as silicone, acrylic, or polymethylmethacrylate (PMMA). IOLs come in different types, including monofocal, multifocal, and toric lenses, each designed to address specific vision needs.