The lens inside in the eye focuses light so the eye gets a clear image whether viewing in the distance or up close. Once the lens is removed, it can no longer focus light inside the eye. There are several methods to restore focusing ability of the eye:
1) a permanent IOL is placed inside the eye
2) a contact lens can be placed on the surface of the eye (contact lenses have to be removed and cleaned regularly)
3) glasses can be used to focus the light rays.
Glasses once the cataract is removed are often very thick and cause magnification, so they are generally not a good option when only one eye is affected. They can also limit the visual field of the affected eye