Quick Question on Prescription Scuba Mask

[Space Whale]

Hello, I'm going on my first dive for SDI certification after having pool training and so forth. I want to purchase a new snorkel mask with prescriptions lens. I did some research, and found out the way you calculate your diopter: 1/2 of the cylinder + sphere = diopter strength. You have to round it down to the nearest decimal divisible by .5.

I did this for OD (right eye) and OS (left eye) and here's what I get:

OD: (.5*-.75)+(-.75) = - 1.125 = (rounded down) -1.0
OS: (.5*-.75)+(-.50) = - 0.875 = (rounded down) -0.5

The issue is I can't find any affordable (<=$60) snorkel masks with a diopter of -0.5 for my left eye, the OS. I can only find a diopter with -1.0 strength.

I was thinking about why not try a -1.0, -1.0 then? Would this give improved vision without having to strain?

 

[John A Lewis]

Have to admit that I've never used the formula that you mention here. Always bought my masks from or sent them to one of the shops that specialized in placing prescriptions into masks. Never had any trouble with the end result, because instead of guessing myself, I had optical professionals do it for me from the prescriptions sent them.

 

[Damselfish]

I'm not remotely an expert on this, but that's not a strong prescription and water has it's own optical effects. You might try whatever mask you've used in the pool for your OW dives and see. You might decide you don't really need correction (which could open up more choices in in affordable dive masks.) Or that you at least don't need it on the .5 side and a plain lens might be better.

If you're looking at masks online and purely focusing on getting something inexpensive with the prescription you think you need, are you ignoring fit? I'd be careful of buying a mask online that you don't know fits you properly. Note that for basic snorkeling you might be able to get away with a less than perfect fit, but the leakage could drive you really nuts when diving.

 

[edwants2dive]

I'm not remotely an expert on this, but that's not a strong prescription and water has it's own optical effects. You might try whatever mask you've used in the pool for your OW dives and see.

I am no expert either but have worn corrective lenses since the 6th grade ( I am now approaching 50 so that's a long time). My normal script is a -4.0 in both Eyes and I would say if you are less than -2 you will be spending money you don't need to. Underwater things will be magnified enough that I would bet you will see fine, topside might be a little blurry but you should be good enough to get to a boat or the shore. Just my opinion.

 

[mswatson]

I am no expert either but have worn corrective lenses since the 6th grade ( I am now approaching 50 so that's a long time). My normal script is a -4.0 in both Eyes and I would say if you are less than -2 you will be spending money you don't need to. Underwater things will be magnified enough that I would bet you will see fine, topside might be a little blurry but you should be good enough to get to a boat or the shore. Just my opinion.

Hi! May I ask if your dive mask has the same prescription as your glasses or - 0.5 lesser than usual? I'm looking for prescription lens for the mask but not sure which is the best for - 4.25 and - 2.75. Some dive stores suggested - 3.5 / - 4.0 or - 2.5/-2.0.