A prescription may only have a sphere power (sph), the powers of the mask usually increase in 0.50 dioptre intervals . Always order the power just smaller than your prescription, for example;Prescription
SPH
If R eye -3.75 then Order -3.50 & if L eye -4.25 then Order -4.00
If you have astigmatism your prescription will look like this.
Prescription:
SPH CYL AXIS
R eye -3.75 / -1.00 x 100
(Add half of the CYL to the Sphere; ie -3.75 + (-0.50) = -4.25)
Order the power smaller than yours if it isn't on the list.
In other words,for the example used Order -4.00
SPH CYL AXIS
L eye -4.25 / -2.00 x 25
(Add half of the CYL to the Sphere; -4.25 + (-1.00) = -5.25)
Order the power smaller than yours if it isn't on the list.
In other words, for the example used Order -5.00
