Cataract Implants

My dad is going to have cataract surgery two day from now. I understood that he is going to need implants after. Why is that? And what are those implants for cataract?

When the cataract, the cloudy lens, is removed, the haze is eliminated, but the focus of the eye must be restored. The lens implants can be folded to permit placement inside the eye through the tiny incision already made for cataract removal and the power of the lens implant is calculated to give the best distance vision possible without glasses. I know that there are intraocular lens implants, made of a type of plastic or silicone, also Bifocals may be necessary to sharpen vision for fine near tasks. And there are new lens implant, the Array lens, has multiple focus points so the needs for glasses are lessened.