Cataract surgery involves replacing the natural opaque lens with a transparent intraocular lens (IOL). Classical IOLs correct myopia, hyperopia, but not astigmatism.
To put it simply, eyes that do not have astigmatism have a cornea whose curvature is close to that of a sphere with a fixed focusing power on its surface. Astigmatic eyes have a cornea that is oval in shape with varying strength on each meridian.
Conventional IOLs do not correct astigmatism. Toric implants can correct corneal astigmatism and thus help target perfect refraction postoperatively. These implants also exist in a multifocal form.
These lenses neutralize astigmatism in the eye. The toric IOL insertion procedure is the same as for conventional cataract surgery. The toric implant should be positioned along an axis measured preoperatively.