How do you prepare the lens blank for spherocylinder lenses?

• A. Mark the axis position before blocking the lens.
• B. Block first, then mark axis.
• C. Polish the backside.
• D. Apply protective film.

Answer: (A)

Marking the axis before blocking is essential because the axis defines the orientation of the cylindrical correction. The block fixes the lens in a precise position for grinding, so attaching the axis reference to the lens first ensures that the intended axis travels with the lens through blocking and edging. If you block first, the lens can shift or rotate relative to the axis mark during mounting or machine setup, risking an incorrect cylinder axis in the finished lens. By marking the axis upfront, you preserve the correct meridian alignment throughout the fabrication process. The other steps described don’t establish or preserve the axis orientation and are not about positioning the cylinder correctly during edging.