Which meridian refers to the lens portion with the least power in a spherocylinder lens?

In a spherocylinder lens, the lens is characterized by its combination of spherical and cylindrical components, which create different powers along different meridians. The axis meridian specifically refers to the orientation of the cylinder within the lens, where there is no additional cylindrical power applied. This means that the axis meridian has the least power in comparison to the other meridians defined by the cylindrical component of the lens.

In practical terms, when an optician measures the various powers required to correct a patient's vision, they identify the axis meridian as the point where the lens has no cylindrical correction. This is typically the reference point from which other powers are calculated, making it essential for accurate fitting and prescription of lenses. Understanding the axis meridian helps opticians effectively manage the correction of astigmatism, ensuring that patients receive optimal visual clarity.