Step 1: Know your prescription and measurements Prescription Your prescription may include a SPH, CYL, Axis, ADD and Pupillary Distance (PD). If your prescription does not include one of these it means that you do not require that corrective power. OD Right eye parameters OS Left eye parameters SPH Sphere indicates the amount of lens power prescribed for nearsightedness or farsightedness CYL & AXIS A Cylinder (CYL) and Axis is required to correct Astigmatism. Both parameters will be required together ADD This provides magnifying power for reading, progressive and bifocal lenses PD The distance between the centres of the pupils...