How to pick the right prescription

by Derek Fu on February 26, 2021

Lenses for our dive masks come in nearsighted (myopia), farsighted (hyperopia), and bifocal readers. Bifocal readers are clear on the top and have magnification on the bottom for reading. Nearsighted and farsighted lenses are single vision. Nearsighted lenses are generally from -1.0 to -10.0 (depending on mask model), Farsighted lenses are generally +1.0 to +5.0 (depending on mask model), and Bifocal readers are usually in the strength of +1.0 to +4.0.

Depending on your prescription information, we will adjust the RX for you. Nearsighted lenses are for people who have trouble seeing distance, and farsighted lenses are for people who have trouble seeing up close.  We strongly advise you follow your prescription or upload it and select “Will upload RX info” as the option. If you don’t know what the numbers mean, then uploading the RX info is highly recommended.

Here is a sample hypothetical prescription below, what we look for is the SPHERE number, that represents the power you need. Cylinder and Axis represent astigmatism values, which we cannot correct for. We however, take the cylinder number, divide it in half, and then add it to the sphere. In the case of a negative number in the sphere (nearsighted), we subtract.


Side  SPH (sphere) CYL (cylinder) AXIS
OD (right) -1.75 -0.50 060
OS (left) -2.25 -1.0 170


Right Side -0.5 / 2 = -0.25 - 1.75 = -2.0

Left side -1.0 / 2 = -0.5 - 2.25 = -2.75 (round down to nearest increment of 0.5 to get -2.5)

If all this is confusing to you, please don't hesitate to contact us via email ( and ask us about what prescription you should pick! Or when placing an order, make sure to upload your RX information so we can see clearly what your needs are. 


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