Which rotation direction is associated with adding to the spectacle axis?

Which rotation direction is associated with adding to the spectacle axis?

• A. Right or CCW
• B. Neither
• C. Left or CW
• D. Both

Answer: (C)

In toric corrections, rotating the lens changes where the cylindrical power is directed relative to the spectacle axis. The axis on a spectacle prescription is the line with zero cylinder, and the power is oriented perpendicular to it. When the lens is rotated in a direction that moves the cylinder’s orientation toward the spectacle axis, more cylinder power is projected along that axis—i.e., it effectively adds to the spectacle axis. That direction is leftward or clockwise when viewed from the front. Rotating in this way brings the cylinder power onto the axis line, increasing the corrective effect along that axis. Rotating the opposite way would move the cylinder away from the axis and reduce the power along it.

In toric corrections, rotating the lens changes where the cylindrical power is directed relative to the spectacle axis. The axis on a spectacle prescription is the line with zero cylinder, and the power is oriented perpendicular to it. When the lens is rotated in a direction that moves the cylinder’s orientation toward the spectacle axis, more cylinder power is projected along that axis—i.e., it effectively adds to the spectacle axis.

That direction is leftward or clockwise when viewed from the front. Rotating in this way brings the cylinder power onto the axis line, increasing the corrective effect along that axis. Rotating the opposite way would move the cylinder away from the axis and reduce the power along it.