What is axis in glasses?

In glasses, the axis refers to a measurement that indicates the orientation of the cylindrical power in a lens. The axis is defined in degrees, ranging from 1 to 180, with 90 representing the vertical meridian of the eye and 180 representing the horizontal meridian.

The axis measurement is important in correcting astigmatism, a common refractive error where the cornea or lens of the eye has an irregular shape, causing blurred vision at all distances. The cylindrical power in a lens is used to correct this astigmatism, and the axis indicates the direction in which the cylindrical power must be oriented in the lens.

When prescribing glasses for astigmatism, eye care professionals will also specify the axis along with the spherical and cylindrical power of the lens to ensure that the correction is accurate and effective. Proper alignment of the axis is crucial to providing clear and comfortable vision for individuals with astigmatism.