When correcting astigmatism, what type of lens is typically used?

Astigmatism is a common refractive error caused by an irregular shape of the cornea or lens, leading to blurred or distorted vision. To correct astigmatism, cylindrical lenses are used, which can be a type of aspheric lens. Aspheric lenses have a more complex surface profile than traditional spherical lenses, allowing them to provide better focus by accommodating the varying degrees of curvature needed to correct astigmatism. They can reduce aberrations and improve the overall quality of vision for individuals with this condition.

While spherical lenses can correct simple refractive errors (like myopia and hyperopia), they are not effective for the specific irregularities presented by astigmatism. Concave lenses primarily address myopia and are not suitable for astigmatism correction. Bifocal lenses are designed to assist with presbyopia, allowing for vision at multiple distances, and do not specifically target the issues of astigmatism. Thus, aspheric lenses are the optimal choice for effectively addressing astigmatism by providing the necessary cylindrical correction.