HELPING YOU CHOOSE THE CORRECT POWER FOR YOUR READY MADE SWIMMING GOGGLES / DIVE MASKS.

A spectacle prescription is usually written in the following form:
Sphere Cylinder Axis
R -3.00 / -0.50 x 180
L -3.50 / -1.00 x 180

In order to calculate the power you need to take into account the two aspects of your prescription.

• The sphere (or sph) is the main part of your prescription and will be ‘–’ for short-sightedness (myopia) and ‘+’ for long-sightedness (hypermetropia).
• The cylinder (or cyl) is the secondary part of your prescription and refers to the amount of astigmatism you have.

You should base the power you order primarily on the amount of short or long sightedness you have. If you also have a moderate degree of astigmatism (up to 2.00), incorporate up to half of this to choose the most appropriate power. Most swimming goggles come in 0.50 steps so you may have to select the nearest power. You need to know the power and sign (+ or -) of both parts of the prescription.

Here are some examples:

-4.00/-1.00 x90 - the best power would be -4.50 (-4.00 plus half of -1.00 so -4.00 plus -0.50)
-2.00/+1.00 x90 - the best power would be -1.50 (-2.00 plus half of +1.00 so -2.00 plus +0.50)
+5.00/-1.00 x90 - the best power would be +4.50 (+5.00 plus half of -1.00 so +5.00 plus -0.50)
+3.00/+1.00 x90 - the best power would be +3.50 (+3.00 plus half of +1.00 so +3.00 plus +0.50

The best Sphere should always be rounded down to the nearest power available never rounded up.

If at any stage you are unsure about the choice of power, just give us a call on 01494 778 200 or email us [email protected]