For exact prescription lenses, it needs to consider several factors. There are two main pieces of information in a prescription:
- The main part is Sphere value (or Sph). They are negative for shortsighted eyes and positive for farsighted eyes.
2. The secondary part of the information is the Cylinder (or Cyl) value. It is to indicate your astigmatism.
Due to the flexibility of the swim goggle frame, it is not easy to include cylinder value into the consideration of lens power as Cylinder is related to a certain angle.
The main solution currently for prescription goggles is to have corrective lenses. They are all premade. The diopters or step diopters are used to determine varied lens power.
Why have corrective lens swimming goggles?
For most swimmers, the corrective lens swimming goggles will fit you well and let you see clearly in the water. It has provided a fast and economical way to have prescription goggles. In addition, it makes it possible to buy this kind of goggles or masks online without face-to-face checking.
If you want to have custom-made prescription goggles, it will normally take about one to two weeks to make. The price of premade corrective lens goggles or masks will be around AUD 40 to AUD 80. In comparison, the cost of custom-made prescription swimming goggles could be up to 10 times higher.
Due to the water blurry environment and reflection, corrective prescription goggles and diving masks are normally manufactured as -1.5, -2.0, -2.5, -3.0 and so on. Lenses are in increments of 0.5. There are no -1.25, -1.75, -2.25 etc. Because it will be hard to feel the difference for -0.25 diopter in the water environment. Premade lens powers are enough to meet your needs.
If you have zero astigmatisms, the swimming goggles with corrective lenses will be like your prescription glasses. If you have low astigmatism, say cylinder value is less than 2.00, the corrective lenses would still fit you well. If you have high astigmatism, we recommend you consult your optometrist or eye doctor first before purchasing. The corrective lens goggles may still be a solution but may not produce the best result as you wear prescription glasses. The reason to consider having a pair of this kind of goggles is its low cost. How much it will be helpful to you and whether it will meet your need to swim or dive can only be judged after you wear the goggles. Again, it will be wise to ask your optometrist or eye doctor’s opinions before purchasing.