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Mrs Zip needs some.
Have seen stick on lenses are they any good or should we go for ready made ones?
Obviously she knows that her current goggles fit which might be a problem with new goggles.
They will only be used for snorkelling.
You mean a mask? The go to always used to be Tusa masks as they sell off the shelf +/- lenses which fit many of their masks - eg. https://www.mikesdivestore.com/collections/tusa-prescription-masks
Remember the air/glass/water interface magnifies things a bit so the prescription you need for diving isn't quite the same as your normal one.
Bought some of the off-the-shelf ones with +/- lenses similar to above for the wife. They've been great. Recommended. No idea about stick-ons but these weren't expensive and they work well so seems better to me as long as the mask fits
Does she actually need lenses? I wear specs but can see fine under water and have never felt the need for lenses on my masks (although I'm usually 30-40m down which might make a difference).
Remember the air/glass/water interface magnifies things a bit so the prescription you need for diving isn’t quite the same as your normal one.
Optician here:
That’s not correct as the front surface of the lens is Plano, the sight test is carried out in air and the rx of the lens is worked on the back surface of the lens, also effectively in air.
The link you have posted looks good though, the individual lens are sometimes better than the insert type, as pressure increases the insert can be pressed towards the eyes which can be a little uncomfortable, for snorkelling this is unlikely to cause a problem.
Have a good one
(although I’m usually 30-40m down which might make a difference).
I would suggest you revisit the more important parts of diving physics if you are diving to 40m and think that may make a difference to the light refraction.
Well given the pressure at depth pushes the glass of the mask closer to your face, so the refraction happens closer to your eyes, I'm going to say, yes, it probably does. However, given on the few occasions I have stayed at snorkel depth, I still have had better visual acuity then when on land without specs, I'll also go with might/might not need lenses.
All purely based on experience, not on any optical physics expertise
Lots of options,
- Tusa do pre-made lenses which are excellent (I happen to like their masks too)
- Theres companies like axis optical who will bond a prescription lens into your existing mask
- You can wear contacts under your mask, as long as you're not dumb enough to attempt a mask clear with your eyes open.
Personally I like the Tusa option, although for free diving I use a teeny tiny super ochio low profile mask, so that one works best with contacts. Those quick/easy stick on's also stick off with similar ease....
/Z
I have lenses stuck to my make and they're fine, want I could get the mask I wanted. However it does mean I need to take my glasses on the boat (and it's a ball ache on the rib) or go blind for the ride out which tends to make me feel a bit queasy.
Prior to that I used contacts with no real issues.
depth pushes the glass of the mask closer to your face
Does it?
How does that work?
All purely based on experience, not on any optical physics expertise
Refractive index of water is 1.333 (air is 1) so everything will appear 33% bigger and 25% closer.
I would suggest you revisit the more important parts of diving physics if you are diving to 40m and think that may make a difference to the light refraction
It will make a difference as you don't get all the wavelengths down there, but whether you can actually see it, I have no idea.
I'd suggest the difference at depth is that 1)your pupil is wide open as there's less light 2) reduced visibility means you're focusing on nearer objects 3)unless you've got a squirt of He in there you'll be feeling some mild effect of nitrogen narcosis so the world will be a better place all round. (and 4, despite being schooled on the prescription thing by someone who actually knows what he's talking about there is still a magnifying effect from the refraction unless you've got a polycarb lens)
If the mask is appreciably closer to your face I hate to think what's happening to your eardrums...
As you dive the water pressure pushes the mask in but you breathe out through your nose which equalises the pressure and moves it back to the right place
I bought a prescription IST Corona M55 diving mask from http://www.prescription-swimming-goggles.co.uk/ and they were really good for the price and more than adequate for snorkelling in the Maldives.
Would recommend quite happily especially as only £58
What is the prescription, some are off the shelf, some are custom made. I use some close to my Rx, and they are excellent, glass lenses so hard to scratch and flat front surface so no compensation needed for the refraction at the water.