Let say, there is a prescription:

SPH: +6.25 D CYL: - 2.50 D

The lens will process in lab from Plastic (PLS), Single Vision (SV), Hi-Index (1.6)

QUERY:

  1. How to calculate (formula) of Blank Lens (Semi-Finish) Diopter to make the above powers?
  2. How to calculate (formula) for Tool Index?
  3. Base Curve - BC (formula)?
  4. Cylender Curve - CC (formula)?
Thanks in advance

Rizwan ul Haque