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Please have a look at some of our help topics below. If you require additional help, please contact us directly and we’ll do our best to answer your questions.

Prescription Goggles Help

How do I choose the proper strength lens?

Choosing the proper strength lens can seem a little confusing, which is why we have provided you with a quick and easy way to determine what lens strength is right for you.

The selection of appropriate corrective lenses for the swimming goggles does require some understanding of your visual acuity requirements and your most recent prescription.

What do I need to do first?

Find out what your existing eyeglass prescription is! The person who tested your eyes or who dispensed your last pair of glasses will have this information and will give you the details. The prescription numbers will contain some uncommon terms, such as:

  • OD – Ocular Dexter (simply means your RIGHT eye)
  • OS – Ocular Sinister (your LEFT eye)
  • Sphere – This measures the degree of weakness in diopters and for nearsighted (myopic) people this is always a (-) negative number
  • Cylinder – This refers to the degree of astigmatism in the eye. In selecting step diopter lenses (which do not correct for cylinder) you must add one half (½) of this number (to a maximum of .50 diopter) to the sphere number to determine the correct step diopter lens!

CAUTION: Ophthalmologists often use a + (positive) number for cylinder and you then have to be careful with the + and – signs when doing the calculations!!

How do I calculate my lens strength?

Determining your correct lens strength can be done easily by using our calculator or manually by using the formula below.

Enter the Sphere and Cylinder values from your prescription to determine which diopter strength would best suit you. Be sure to select + or - for each and enter all four values.
*This measurement is only a suggestion. It is best to confirm your diopter strength with your optometrist.
SphereCylinderDiopter Strength
O.D. (right eye)  
O.S. (left eye)  


SPH____ + 1/2 Cyl ____ = _____


For example,

  • If the sphere (Sph) is -2.5 and the cylinder (Cyl) is -1, then -2.5 + (1/2 x -1) = -3 step diopter lens: Adding -2.5 and -0.5 together
  • If the sphere is -4.0 and the cylinder is +1, then -4.0 + (1/2 x +1] = -3.5 step diopter lens: Adding -4 and +0.5 together

*Note that we do not recommend moving more than 0.50 in either direction,.


In situations where the cylinder is 0, the same formula is still used.

For example,

  • If the sphere is -2.5 and the cylinder is 0, then -2.5 + (1/2 x 0) = -2.5 step diopter lens
  • If the sphere is -4.0 and the cylinder is 0, then -4.0 + (1/2 x 0) = -4 step diopter lens

See, simple! By plugging in the appropriate values into the formula above, you can determine what lens strength you need for your Aquagoggles prescription goggles!

Do not move more than a 0.50 diopter step in either direction from your sphere.
If you have any questions, don’t hesitate to contact us


There is also a great tool at Glasses Simulator

Special Considerations

In order to produce lenses for swimming goggles, and keep the price reasonable they are made in one-half (.5) dioptre increments. These lenses are not a full custom prescription and do not correct for cylinder or astigmatism. They are not intended for full time wear. Extended wear of step dioptre lenses will cause various degrees of eye strain but they are more than adequate for occasional wear especially if the cylinder is close to or less than 1.

Always move DOWN to the closest step dioptre! If calculation of your prescription shows that you should have a -2.75 (step dioptre lens) then you should choose a -2.5 lens for the swimming goggles. This causes less strain and you will be unlikely to notice any significant loss of acuity within a reasonable distance. There is also a slight magnifying effect when underwater.

Getting used to Step Dioptre Lenses

The corrective lenses in these swimming goggles do not have correction for cylinder and are not a direct match for your regular prescription but are more than adequate for temporary use.

A number of swimmers have told us that it takes a short while to adjust to their goggles. Wear them for a few minutes, your eyes will adjust and you will be more than satisfied with the results! Enjoy your swimming experiences and please drop us an email with your comments.

Fitting and Care Instructions

We appreciate your business and trust you have received your order in perfect condition. If there is a problem with your order, please contact us so that we may correct this issue as soon as possible.

Please note that the goggle lenses are of step diopter construction. This means that they will not exactly match your prescription and are not meant for prolonged use. Aquagoggles are recommend for recreational swimming and should not be used for diving or other high-impact water sports. Careless or inappropriate use can cause injury.

Fitting your goggles

Goggles come pre-assembled with the seal/strap combo already in place. All you have to do is adjust the head strap tension to suit your size and comfort. Remember, tighter is not necessarily better, as this may cause discomfort and markings around the eyes.

Goggles are also shipped with Small, Medium and Large sized nosepieces. The Medium nosepiece comes pre-installed. If the goggles do not fit right, stand in front of a mirror with the goggles held to your eyes and without the nose bridge installed. Find the most comfortable position. Select the nosepiece that best fits your comfort position (the space between the lenses) and clip the nosepiece in place.

Removing the nosepiece

Firmly grip the outside of an eyecup piece and the nosepiece. Carefully pull on the nosepiece until it pops out. A small twist and pull motion may be needed as the nosepiece fits quite snuggly.  For a demonstration, Aquagoggles Youtube!

Removing and replacing seal/strap

Removing the seal/strap is easy since the Silicone stretches. Carefully pull the seal, starting with the widest end, away from the lens. Pay close attention to how the seal is removed since you’ll be replacing it in the same position. It’s much easier to remove and install with the nosepiece removed. To install, start with the narrow end of the lens and insert it into the narrow end of the seal. There will be a slit in the middle of the seal for the lens to fit in. Push the lens as far down into the seal as possible (try to get it as close to centered as possible as well), then pull the seal forwards and push the other end into the top of the lens cup groove, then work the seal around the lens into the molded retaining groove. A rolling and pushing action with your thumb will help insure a full seal. You will faintly see the seal in the groove of the lens. This will ensure that the seal is on the lens properly.

Click here to watch a demonstration on Youtube.

Adjusting strap

When adjusting the straps for correct tension, DO NOT PULL on the ends of the straps BEFORE you have slid the end sideways out of the last retaining ring on the clip! This end half loop has an edge that can “nick” the silicone strap and then result in tearing. Note: Do not over tighten, silicone seals do not require much compression to seal properly.

Eyecup Seal

The eyecup seals are part of the strap assembly and fit tightly around the lens itself. If you do peel off this seal for any reason it can be replaced but you do have to stretch & push/roll the seal inwards to get a proper seal. This will take some time to accomplish!


These lenses have been coated with an anti-fog solution during manufacture. This coating will scratch easily and soap or other surfactants can damage the coating. Rinse and shake to dry ONLY. Using fingers, tissues or cloth will scratch the anti-fog coating inside the lenses.

Removal of Anti-fog coating

If you have scratched the coating inside the lens or damaged it by using detergents or other surfactants there is a solution! You can use isopropyl alcohol (rubbing alcohol) to remove all of the factory applied coating. Pour some alcohol inside the lens & let sit for a few minutes then use a finger tip to rub around the inside of the lens, removing the coating and then rinse under hot water. It is not necessary to remove the silicone seals or strap as alcohol will not affect the silicone. Now you have an untreated poly carbonate lens!

Additional instructions are included with your goggles (blue insert).

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