+1.75 or +3.00?

[ChrisTull]

My eyes need some assistance to read the gauges. My current prescription, which didn't change since my previous exam four years ago, is OD: +1.75 and OS: +0.75 with a slight astigmatism, and ADD of +2.50 for both eyes. I am 67 years old.

I was considering buying some off-the-shelf bifocals with these values for my Mares X-Vision mask. But when I tried on some inexpensive reading glasses in Walmart I could easily read my watch at close range only with +3.00 glasses. +1.75 glasses were no good at all.

Does that mean I should order mask lenses with +3.00?

 

[Storker]

Rule of thumb: If you want to "correct" astigmatism with spherical correction, halve the cylinder prescription. Also, you'll have to add the distance (spherical) correction to the close range correction. If you're +1.75(L)/+0.75(R) hyperopic and have an additional +2.50 presbyopic correction, the sum for close range correction is +4.25 for your right eye and +3.25 for your left eye, and +1.75 right and +0.75 left for distance.

With +3.0 on both eyes, you'll have decent close-range vision with your left eye, and you'll be about +1 hyperopic at close range (but -0.75 myopic at distance, i.e. workable but not ideal) on your right eye. Not considering your astigmatism. Personally, I'd go for different correction for left and right eye, and consider reading bifocal lenses for being able to read the computer.

 

[NAM001]

Chris
I have always been told that water is about a +1 or better correction in its self. So if you need 3.0 in glasses Then a 1.5-2.0 would go in your mask to add to the +1 of the water. When you have lenses put in your mask you give them your glasses script and they do the adjustment for the water factor. I need a 2.5 also and NEED nothing n hte mask. to dive however i have a mask that has corrective lenses in them and they work fine also. I am sassuming that the +2.5 needed is changed to a 1.5 after water correction and my eyes are probably straining to adjust enough for my mind to do the rest. I also have a mask with a 1.5 in lower portion of them and it looks works good for gage reading. I am far sighted. The masks that work the best for me is the ones with the unchanged front pane and another pane in the lower with gain for gage reading. The lower comes factory with +1.5 gain in it. PLUS i use a predator/petrel so it has a large screen to boot.

 

[ChrisTull]

Rule of thumb: If you want to "correct" astigmatism with spherical correction, halve the cylinder prescription. Also, you'll have to add the distance (spherical) correction to the close range correction. If you're +1.75(L)/+0.75(R) hyperopic and have an additional +2.50 presbyopic correction, the sum for close range correction is +4.25 for your right eye and +3.25 for your left eye, and +1.75 right and +0.75 left for distance.

With +3.0 on both eyes, you'll have decent close-range vision with your left eye, and you'll be about +1 hyperopic at close range (but -0.75 myopic at distance, i.e. workable but not ideal) on your right eye. Not considering your astigmatism. Personally, I'd go for different correction for left and right eye, and consider reading bifocal lenses for being able to read the computer.

Thank you for a detailed answer. It's a bit of an overkill for me, and you've mixed up my eyes. I have +1.75 in OD, which is Right.

Let me put it simply: I bought a +3.00 cheap reading glasses and brought them home. When I put on my mask and look through its plain lenses AND the +3.00 reading glasses placed on top of mask lens (touching it), my vision is perfect! I can read my wrist computer/watch at close range better than with my prescription glasses.

My reasoning is. If instead of my "experimental lens" I will have bifocal Mares lens - I will see my gauges perfectly. Right now, LeasurePro has Mares Bi-Focal Corrective Lens for X-Vision/Liquid-Skin Mask for a very reasonable price.
Also, it's important that I never use any glasses except when I read or work on computer. I drive, walk and live all day long without glasses, and I don't feel any need for them because my distance vision is nearly perfect (95%).
Since you are so specific about all the optical info, my full prescription is:
OD SPH +1.75; CYL -1.00; AXIS 075; ADD +2.50
OS SPH +0.75; CYL -0.25; AXIS 037; ADD +2.50

---------- Post added August 2nd, 2014 at 05:15 PM ----------

Chris
I have always been told that water is about a +1 or better correction in its self. So if you need 3.0 in glasses Then a 1.5-2.0 would go in your mask to add to the +1 of the water. When you have lenses put in your mask you give them your glasses script and they do the adjustment for the water factor.

I am ONLY interested in optical magnification in the bottom part of my mask lenses - to read the numbers for safety and to select settings for photography. I can see the underwater world in the distance PERFECTLY without any correction lenses.
Water magnification in my opinion and from what I saw does little to improve clarity. All I could see was a larger image of my blurry Suunto Vyper's screen.

 

[musicalmike]

There are two products available that will work for you. Dive Optx and Aqua Optics. Both can be added to the bottom portion of your mask and act as bi-focals. They are available in positive diopters from 1.0 to 3.0 in .250 increments. The difference between them is how they are affixed to your mask and the material they are made of. Dive optx are a soft flexible clear vinyl with a slight concave shape. They are applied with water and pressed firmly into place. Once the water has evaporated the lens is secure. The Aqua Optics are a optical quality flat glass. Uses a water soluble glue for adhesion. Both are removable and cost is comparable @ around $30. Unfortunately they are only sold in pairs with the same magnification for each eye. In my experience it really doesn't matter what your correction #s are. The purpose is to magnify the objects in question. Therefore you may find that the more magnification you have the better you can see. They are distributed by Trident and can be ordered through your local dive store.

 

[Doc]

Whatever your experimentation, it will differ once u/w.

You can test such things in a bath tub.

I have produced happy results for friends by using reader glasses from the Dollar Store. Remove the lens, of cut them apart. Test them, if you like the result, they can easily be long-term mounted (yet quite removable) from the faceplate by securing them with a dab of Goop brand adhesive. (On the edges!)

Or or you can spend $30 on one at a dive shop.

 

[ChrisTull]

Both ideas are good. Will proceed with Doc's first since i got several pairs of cheap reading glasses. One question, lenses are slightly curved, and when attached with Goop with dabs on edges will leave air between the mask faceplate and them. Problem?

 

[Storker]

Thank you for a detailed answer. It's a bit of an overkill for me, and you've mixed up my eyes.

Yup, sorry for that.

Let me put it simply: I bought a +3.00 cheap reading glasses and brought them home. When I put on my mask and look through its plain lenses AND the +3.00 reading glasses placed on top of mask lens (touching it), my vision is perfect! I can read my wrist computer/watch at close range better than with my prescription glasses.

[...] Also, it's important that I never use any glasses except when I read or work on computer. I drive, walk and live all day long without glasses, and I don't feel any need for them because my distance vision is nearly perfect (95%).

Figures. See below.

Since you are so specific about all the optical info, my full prescription is:
OD SPH +1.75; CYL -1.00; AXIS 075; ADD +2.50
OS SPH +0.75; CYL -0.25; AXIS 037; ADD +2.50

Let's do the math. Semi-correction of a cylinder Rx is about 50% in spherical (at least that's what my optician recommended when I couldn't get contacts with the correct cylinder Rx for my right eye).
OD distance: +1.75 +0.5*(-1.00) = +1.25
OS distance: +1.25 + negligible = +1.25
+1.25 ain't much. A slight hyperopia may not be a huge problem at distance. Myopia, OTOH...

OD close: +1.75 +0.5*(-1.00) + 2.50 = +3.75
OS close: +1.25 + negligible + 2.50 = +3.75

IOW, +3.00 on both eyes will correct your near vision pretty well, but you'll be myopic at distance. I don't know if you're using a wrist computer with small numbers on it, like a Suunto D4, or a console-mounted computer with larger numbers, often read at a little more than normal book reading distance. If the latter, +0.75 at "reading" distance shouldn't be a problem at somewhat longer distances. I'm somewhat presbyopic myself (Add +2.00), and my correct desktop computer Rx is Add +1.00.

I am ONLY interested in optical magnification in the bottom part of my mask lenses - to read the numbers for safety and to select settings for photography. I can see the underwater world in the distance PERFECTLY without any correction lenses.

I have problems believing "perfectly". "Good enough", I can believe. Again, a slight hyperopia may not be a huge problem at distance.

I'm considering those add-on bifocal type lenses myself. Currently, I'm using progressive contacts, and although they work decently in many situations, I sometimes have problems keeping my camera screen in focus.

 

[ChrisTull]

+3.00 Mares lenses for X-Vision mask is what I purchased online. Will let you know the results. Thank you all for your help.

 

[diver 85]

"Does that mean I should order mask lenses with +3.00?"......If I understand you correctly Chris, you're considering ordering a +3.00 for each eye??........(Since we're all dry labbing this problem--ie hyperopic presbyopia, I'll throw my 2.5 cents in)--.....You'll might have a problem, due to the anisometropia(unequal prescriptions between the 2 eyes)----but, if you're only considering OTC stuff, I'd try a +2.50 for each...You'll be a little over powered in the right eye(by .75 diopters) & about 2 diopters over powered in the left eye....The right will see "OK" @ a distance(underwater) & the left eye will see fairly well @ near(underwater)..So--effectively you've monovisioned yourself-----with (basically) glasses ie the mask will have a vertex distance of ?maybe 15 to 20 mm & glasses usually have a vertex distance of about 11 to 12 mm(vertex distance is the distance between the front of the eye & the back of a lens)....Most of the time we monovision people with contact lenses(zero vertex distance)----but, you'll be getting what you paid for........

---------- Post added August 4th, 2014 at 08:40 AM ----------

+3.00 Mares lenses for X-Vision mask is what I purchased online. Will let you know the results. Thank you all for your help.

Can you order a 2nd pair(ie +2.50) & return the 'worse of the 2'???.........See my 'theory' above....good luck & let us know how things work out...interesting with the anisometropia coming into play......