What does the axis measurement indicate in relation to astigmatism?

The axis measurement in relation to astigmatism specifically indicates the degree of angle at which the cylindrical portion of the lens is oriented. In astigmatism, the eye has an irregular shape, causing light to focus on multiple points rather than a single point on the retina; this irregularity is corrected with cylindrical lenses that have a specific orientation.

The axis measurement is defined in degrees, ranging from 0 to 180, and it denotes the meridian of the eye that is most and least affected by astigmatism. This alignment ensures that the cylindrical lens is correctly positioned to counteract the uneven curvature of the cornea or lens.

Understanding the axis is crucial for effective vision correction, as using the correct orientation minimizes visual distortions and provides clearer vision for individuals with astigmatism.