Choosing Prescription Lens for swimming goggles

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

First Step: 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:

Terms:

OD	Ocular Dexter (simply means your RIGHT eye)
OS	Ocular Sinister (your LEFT eye)
Sphere	This measures the degree of weakness in dioptres 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 dioptre lenses (which do not correct for cylinder) you must add one half (½) of this number (to a maximum of .75 diopter) to the sphere number to determine the correct step dioptre 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!!
Examples	Sphere is -2.5 and cylinder is -1, [-2.5 + 1/2 of -1] = -3 step dioptre lens Sphere is -4.0 and cylinder is +2, [-4.0 + 1/2 of +2] = -3 step dioptre lens In both of these examples a -3 dioptre aquagoggle lens would be best. Examples if you have "0" cylinder Sphere is -2.5 and cylinder is 0, [-2.5 + 1/2 of 0] = -2.5 step dioptre lens Sphere is -4.0 and cylinder is 0, [-4.0 + 1/2 of 0] = -4 step dioptre lens.

	Sphere	Cylinder	Step Dioptre Calculation
Right Eye (OD)	__________	__________	____ +½____ =______ Right Eye
Left eye (OS)	__________	__________	____ +½____ =______ Left Eye

Step Dioptre Lens - 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.

Fitting your prescription swimming goggles

The use of high quality silicone seals means that less pressure is required to form a good leak proof seal and this also helps in fitting a wide range of facial shapes and sizes.

Getting a good seal is only possible if you choose the correct nose bridge size. This is really the only adjustment possible except for the head strap tightness. It is also important for minimizing eye strain to set the goggles distance between eyes. That's why we supply four different bridges when most companies give you one. We recommend fitting the nose bridges and checking for a good seal before fastening the head strap.

Silicone seals are basically "suction devices", if properly positioned over the eye you can gently push in on the lens and the seal should form a small vacuum under the cup when you release the pressure. In order to properly position each cup you must adjust the nose bridge S, M or L or use the adjustable silicone covered band, so that both eye cups seal properly.

The strap should be adjusted so that it is just tight enough to seal properly. These silicone seals require lower pressure than cheaper PVC seals.

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.