Use this formula for each eye separately: .

If SPH is +1.00 and ADD is +1.75 , your reading power is +2.75 .

Your eyes turn inward when reading, so your "Near PD" is typically 2-3 mm narrower than your "Distance PD".

If your prescription has Cylinder (CYL) and Axis numbers, copy them exactly; they do not change for reading glasses. 2. Adjust Your Pupillary Distance (PD) PD is the distance between your pupils in millimeters.

To buy reading glasses using a prescription, you must use your distance and Addition (ADD) values to calculate the correct lens power . 1. Calculate Your Reading Power

If SPH is -2.00 and ADD is +2.25 , your reading power is +0.25 .