How to Read a Prescription Scuba Mask

Both fresh water and sea water make objects appear larger, though some scuba divers insist on submersible corrective vision. These special lenses can either be mounted inside existing lenses or custom made to replace the stock lenses. Reading a prescription scuba mask is a lot like reading a prescription for eyeglasses. The only difference is these lenses are made to withstand additional atmospheric pressures under water and they are scratch resistant.

Things You'll Need

  • Scuba mask
  • Prescription lenses
  • Lens prescription
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Instructions

  1. Reading the Sphere

    • 1

      Obtain a copy of the lens prescription. A lens prescription will list information for both the right and left eyes.

    • 2

      Find values for the oculus dextrus (OD), the right eye, and oculus sinister (OS), the left eye. Though rare, the prescription could show oculus utro (OU), both eyes are affected the same.

    • 3

      Understand the OD and OS values. Both numbers are expressed in diopters, which describes the power of lens needed to correct vision to 20/20. Negative values indicate nearsightedness, while the positive values indicate farsightedness. An OD of -1.00 and an OS of -1.25 would indicate relatively mild nearsightedness. A diopter value of -4.75 is more than four times the values given in the example and would require thicker lenses to correct.

    Reading Additional Information for Astigmatisms

    • 4

      Locate the OD and OS values for C. The value for C describes the cylinder, which is the degree of astigmatism in each eye. This number is reported in diopters, the same as for the sphere. Just like for the sphere, this number can also be positive or negative.

    • 5

      Read the axis. This describes the orientation of the astigmatism. While no units are given, the measurement is in degrees. The reported value will range between 0 and 180 degrees.

    • 6

      Combine all the information. For prescriptions with astigmatisms, the information is reported in the order of sphere, cylinder, and axis. So, a prescription of -2.25 by +1.50 by 45 indicates 2.25 diopters of nearsightedness, 1.50 diopters of astigmatism, with an axis of 45 degrees.