What measurement is associated with the "AXIS" in contact lens prescriptions?

The measurement associated with the "AXIS" in contact lens prescriptions refers to the degree of astigmatism correction. In optics, astigmatism is a condition where the cornea or lens is irregularly shaped, leading to blurred or distorted vision. To correct this, the axis indicates the orientation of the cylindrical power needed to correct the astigmatism.

The axis is measured in degrees and typically ranges from 1 to 180. It specifies the specific meridian along which the cylindrical correction is applied, ensuring that the lens effectively compensates for the unequal curvature of the eye's surface. This targeted correction is essential for achieving clear vision for individuals with astigmatism.

The other options don't relate to the axis measurement. The size of the lens in millimeters pertains to the overall diameter of the lens, while the curvature of the lens refers to its physical shape and how it conforms to the eye's surface, neither of which directly addresses the astigmatism correction. Wearing time in hours focuses on how long the lenses should be used but does not provide any information about the prescription itself.