How to Choose the Correct Optical Lens

Snorkel-Mart offers pre-ground step diopter optical lenses for people requiring snorkeling and dive masks with optical correction. The lenses we offer are known as "Step Diopter" lenses, which basically means stock or pre-fabricated lenses. Our stock prescription lenses provide what most optometrists will refer to as a "spherical equivalent". The calculation that we use(half the CYL value added to the SPH value) has worked really well for our thousands of satisfied customers to correct vision under the water. These optical lenses are in stock and ready to be installed into the prescription masks made by Deep Blue Gear.

Use Our Rx Optical Lens Calculator to Calculate Your Recommended Prescription

Enter the Sphere (SPH) and Cylinder (CYL) values from your prescription into the Optical Lens Calculator below and click the Calculate button to determine which of our rx lenses would best suit your needs. *Note: If your Cylinder value is greater than +2.5 or less than -2.5, please contact us at (888) 597-8445 to learn about obtaining custom ground lenses.

  • Eye
    +/- Sphere
    +/- Cylinder
  • ${calculator.title}
    ${ calculateLens(calculators[index]) }

*Note: In addition to selecting the dropdown choice for positive (+) or negative (-) lenses, please remember to insert decimal points. Sometimes doctors get in a rush and do not put the decimal point in the actual prescription, but most sphere and cylinder values have decimal points. Example: -075 is the same as -0.75 or +550 is the same as +5.50.


Learn More about How To Choose an Optical Lens

Please watch the video below if you would like to see an overview of how to use the optical lens calculator on our website.