Ophthalmologists write astigmatism prescriptions with positive (+) cylinders. Most eyeglass labs, including ours, cut lenses in the negative (-), and require that any positive (+) cylinder prescriptions be converted into the negative (-) equivalent. Rest assured this conversion does not alter the type or quality of the vision correction that your doctor prescribed you. The conversion will affect (change) the SPH, CYL, and AX parameters in your prescription, but will result in the exact same vision correction you were fit for by your doctor.
We automatically perform this conversion if the prescription you enter is written with a positive (+) cylinder, but if you would like to get the conversion of your positive cylinder prescription, you can do so by using the Positive Cylinder Conversion tool below.
Still have questions? Call us at 1-888-248-5367 to speak to one of our trained Customer Service Representatives.
The positive equivalent is shown above.