Can’t I just get “off the shelf” lenses from my dive-shop?
Certain mask manufacturers offer a limited range of replacement ‘corrective’ lenses, which actually fill the entire lens aperture. However, as these come in a limited range of prescriptions, go in half dioptre, as opposed to quarter dioptre, increments and make no correction for astigmatism ( the Cyl. Part of a prescription ), they are only suitable for a small percentage of people.
It’s a bit like buying ‘off the peg’ clothes… If you are lucky enough to have a prescription of, for example, +2.50 right eye sphere and -1.00 left eye sphere, there will be dive-shop lenses that ‘fit’ you perfectly.
However, if your right prescription contains figures like -2.25 Sph. with -1.25 Cyl. an Axis of 135 and a +2.25 add, you are going to need precise ‘made to measure’ lenses. Moreover, as sight4sport is run by a qualified optometrist, you can be confident that Dive-Vision will give you the best advice and that the prescription is correct and the lenses are set to your optical centres (inter-Pupilliary Distance ), an important factor in giving you optimum underwater vision. We are also able to advise and cater for very high corrections ( above +/-10.00 Sphere and 4.00 Cyl ) and to allow for prism, where applicable.
Why not just wear contact lenses?
No reason whatsoever… except, of course, for a little protozoa, called Acanthamoeba. This lives in both salt and freshwater and can cause Acanthamoeba Keratitis, which is an infection of the cornea - the front part of the eye. This is a painful, sometimes permanently damaging condition which can result in a corneal graft… or even the loss of an eye! A contaminated contact lens greatly increases this risk.
Secondly, if your mask floods, there is the risk of a contact lens being displaced… which is inconvenient to say the very least. But this can have an even more serious outcome… The higher osmolarity of seawater, or lower osmolarity of freshwater, when compared to tears, can cause soft contact lenses to adhere to the eyes. To ‘unstick’ them will require irrigation with isotonic saline, something that is not readily available on most beaches or dive sites!
Soft contact lenses can also absorb proprietary ‘de-fogging’ solutions, which can cause eye irritation. Another good reason not to wear them.
Last but not least, some divers who wear hard or gas-permeable contact lenses, can experience blurred vision after diving. This is because gas is under pressure in the mask, causing the tears to absorb nitrogen. When the diver surfaces at a normal rate, the tears and cornea are unable to eliminate the inert gas as quickly as they would without the contact lenses in place, causing bubbles to form between the lenses and cornea, which will affect the surface of the cornea, causing the blurring.
Does being under the water alter the prescription?
Can you recommend a mask?
Are all masks suitable for all prescriptions?
Can you do varifocal lenses?
Sorry, there are no varifocal lenses available for dive masks, not from us or anyone else. Again, this is simply because there are no flat-fronted, lens blanks made that would enable us to do this.
However, we can supply bifocals… in fact, they probably account for some 50% of all the orders we receive. These look like one single piece of glass, with a small, virtually indiscernible, 28mm reading segment at the bottom. This segment is well out of line of sight when you are swimming ahead, but positioned to be exactly in line of sight when you want to read your computer or gauges, check camera settings or look at anything up close. ( To see what these look like, Click here )
We carefully set the height of the top of the segment depending on the make and model of mask. However, we can vary this for specific applications, such as photography, where we can, for example, provide a much larger read area if required.
How are the prescription lenses attached?
Will you be replacing the complete lenses?
If there were, the edge thickness of higher correction minus lenses and the centre thickness of plus lenses, would make the lenses very heavy.
We endeavour to make the lenses as thin and light as we possibly can, for any given prescription.
Some mask manufacturers do supply replacement, corrective lenses, "off the shelf". These are often for minus corrections only, they make no correction for astigmatism ( Cyl.) and are only available in half, as opposed to quarter dioptre increments. As specialists in 'precise prescription' glazing... exactly the same as the prescription in your everyday glasses or contact lenses, we do not supply 'off the shelf' lenses. Moreover, many masks do not have removable lenses.
What if I recommend a friend?
Can I get a discount on a second mask?
What if my prescription changes?
No problem. When we heat the lenses in an oven to extreme temperatures they can be removed and new lenses put into the mask.
There is a charge for the new lens and fitting.
Can I use defogger on my dive mask & lenses?
Have you ever had a lens come off a mask?
We guarantee them for life.
What happens if I break a lens or the face plate?
Can you put any prescription in any mask?
Some powers are Standard Range, others fall in to High Prescription (HP) but we have glazed powers from + 20.00 to – 15.00.
Where in the mask do you place the lenses?
From experience we know the best position in all of the popular masks on the market.
1) Bifocal height is set ergonomically to suit the head position when diving.
2) Photographers need a high bifocal to read details from the camera.
3) We have to match the centres of the lenses to the distance between your pupils, for the best vision, to prevent visual discomfort and to produce the most suitable lens thickness. High powered lenses may need higher volume masks.
4) Call us if you want to send us your own mask and we’ll go through the process with you.
What do you need to know about my prescription to put it into a mask?
2) The distance between your pupils. This helps us set up the lenses to give you the best vision and prevent any unwanted effects on the power.
3) If you have any particular special needs when diving e.g. Photography, interest in small marine life etc. We can make adjustments to the prescription.
4) If you are over 45 you may need a reading only segment or bifocals to clearly see your gauges or computer, as the muscles in your eyes make near vision more difficult………`your arms aren`t long enough!
I have Astigmatism
What if I need a specialist prescription like bifocals?
Can I get my precise prescription in any mask?
Or you can even send us your own dive mask and we’ll put your prescription in it although this will take a little longer because of having to post your mask to us.