In terms of lens design, what defines a toric lens?

A toric lens is defined by its design that incorporates both spherical and cylindrical curves. This combination allows the lens to correct for astigmatism, which is an optical condition resulting from an irregularly shaped cornea or lens in the eye.

The spherical curves help in correcting myopia (nearsightedness) or hyperopia (farsightedness), while the cylindrical curves specifically address the asymmetry in the curvature of the eye that causes astigmatism. This dual design distinguishes toric lenses from other types of lenses.

While other options mention variations of curvature, they do not accurately describe the essential feature of a toric lens, which is the integration of both spherical and cylindrical curves to provide optimal vision for individuals with astigmatism.