At Oceans Optics, the goal is simple: clear, comfortable vision in a diving mask with prescription lenses. Choosing the right power for your prescription snorkel mask or prescription scuba mask starts with understanding how light behaves underwater and how to read your glasses prescription.
Start with your prescription (SPH only)
Use the Sphere (SPH) value for each eye.
Negative (−) SPH = nearsighted (myopia)
Positive (+) SPH = farsighted (hyperopia)
*Stock mask lenses are spherical, so ignore Cylinder/Axis (astigmatism) for off-the-shelf options.
Why underwater needs a slightly weaker lens
Water + mask create a virtual image that looks ~25–33% closer/larger. To match this underwater magnification—and avoid over-correction—use a slightly weaker power than your glasses.
Simple adjustment we recommend:
Reduce your glasses SPH by 0.50 to 0.75 diopters (toward zero), then choose the nearest 0.50 step we stock.
Quick examples (nearsighted)
OD (Right): SPH −3.00 → Choose −2.50 (−0.50) or −2.25/−2.00 if you prefer a softer, long-day feel—pick the nearest step available.
OS (Left): SPH −2.75 → Choose −2.25 (−0.50) or −2.00 (−0.75); select the closest stocked step (−2.50 or −2.00) if 0.25 steps aren’t offered.
Rule of thumb: pick −0.75 for longer sessions to reduce eye strain; pick −0.50 for shorter swims or extra-crisp distance (gauges, photos).
Final checks
Choose each eye individually (L/R powers can differ).
Prioritize a good mask fit (S/M vs M/L, soft silicone skirt, tempered glass) so your chosen power performs as intended.
Have significant astigmatism or special requirements? Consider custom lenses or speak with your eye care professional.
Swim into clarity with Oceans Optics prescription lenses—built for relaxed, sharp underwater vision on every trip.
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