How to Read a Prescription Scuba Mask

How to Read a Prescription Scuba Mask
While objects underwater do appear larger than they really are due to the refractive effects of water, those who need eyeglasses or contacts should still look into getting a prescription scuba mask if they intend to dive frequently. After all, the point of diving in the first place is to see things, and the best way to do that is by getting a prescription dive mask.

Instructions

Difficulty: Easy

Things You’ll Need:
  • Existing eyeglasses or contacts prescription
  • Existing eyeglasses or contacts prescription
Step 1
Look at your existing eyeglasses prescription and note the numbers for OD and OS. These are diopter measurements, with OD being for the right eye and OS for the left eye. Diopter refers to focal distance, with the number serving as the denominator of a fraction of a meter. So, for example, a diopter of -5 means a focal distance of 1/5 of a meter, while a diopter of -3 means 1/3 of a meter.
Step 2
Apply those numbers to shopping for a prescription scuba mask. Most manufacturers make standardized masks where the OD and OS are the same, ranging between -1 and -5, with a few manufacturers going -8.
Step 3
Compare those numbers and decide if they are right for your needs. Most people, for example, rarely have ODs and OSs that are the same, but the standardized masks are all made that way. If you want a mask with two different corrective lenses, you will need to get that specially made at the factory. Likewise, very specialized lenses, such as bifocals or those beyond -8, will need to be ordered from the factory.

Tips & Warnings

 
Keep in mind that water refraction makes everything underwater look bigger, and that even the clearest waters rarely exceed a visibility of 100 feet. Under circumstances like that, most eyeglass or contact wearers really only need a mask that approximates their prescription. It does not need to exactly match it. Water refraction also counters any and all problems with astigmatisms, so do not worry about that when reading a prescription dive mask.
 
Keep in mind that water refraction makes everything underwater look bigger, and that even the clearest waters rarely exceed a visibility of 100 feet. Under circumstances like that, most eyeglass or contact wearers really only need a mask that approximates their prescription. It does not need to exactly match it.
 
Water refraction also counters any and all problems with astigmatisms, so do not worry about that when reading a prescription dive mask.

Article Written By Edwin Thomas

Edwin Thomas has been writing since 1997. His work has appeared in various online publications, including The Black Table, Proboxing-Fans and others. A travel blogger, editor and writer, Thomas has traveled from Argentina to Vietnam in pursuit of stories. He holds a Master of Arts in international affairs from American University.

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