What kind of lens characteristic is specifically used to correct astigmatism?

Cylinder power is specifically used to correct astigmatism because astigmatism is a refractive error caused by an irregular shape of the cornea or lens, resulting in blurred or distorted vision. This condition occurs when light rays do not focus evenly on the retina, leading to images being out of focus in one direction (horizontal or vertical).

To correct this, a cylindrical lens with a specific cylinder power is prescribed, which has different refractive powers along different axes. The cylinder power helps to compensate for the uneven curvature of the cornea, ensuring that light rays are focused appropriately on the retina. Consequently, the lens is designed to correct one meridian while leaving another meridian untouched, thus addressing the unique visual needs of individuals with astigmatism.

In contrast, sphere power pertains to spherical lenses and is used to correct myopia or hyperopia, while prism power is used to address alignment issues or strabismus. Base power is not a commonly recognized characteristic in standard vision correction terminology. Therefore, cylinder power is imperative for appropriately addressing astigmatism.