Question: how to calculate your eye power?
Answer: However, you have to do a little algebra to figure the total power needed for single-vision reading glasses. In the example above, it is -2.00 +1.75 = -0.25. So the prescription for reading glasses for the right eye would be -0.25 – 0.50 x 180. For the left eye, the calculation is +1.75 +1.00 = +2.75 D.S.