The increase of power in the correction of astigmatism is measured in what unit?

The measurement of power in the correction of astigmatism is expressed in diopters. Diopters are a unit of measurement that quantifies the optical power of a lens, which indicates how much the lens can bend light to correct vision. In the case of astigmatism, which arises from an irregular shape of the cornea or lens, the optical correction varies depending on the direction of the light rays being focused.

The power required to correct astigmatism is typically indicated in positive or negative diopters, depending on whether the lens is convex or concave. The higher the diopter value, the greater the lens' ability to converge or diverge light, thereby correcting the refractive error. Understanding this measurement is crucial for optometric technicians when assessing and fitting lenses for patients with astigmatism.

Other units mentioned, such as degrees, millimeters, and centimeters, do not measure optical power. Degrees might be used for measuring angles, millimeters and centimeters are linear measurements, but none relate directly to the optical power needed for lens correction. Therefore, diopters is the correct and relevant unit for this context.