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Dale
09-18-2007, 11:44
I'm farsighted with correction from infinity down.

Here is the question. I have a Mares ESA Six mask and have the proper close up correction in the lower lenses.

But, I'm a bit curious as to what I want to use for the distance in the main lenses.

I'm doubtful that I need the correction appropriate for infinity for two reasons. First, things appear close, so infinity is likely to require a bit more correction than it would in air. Right/Wront?

In air, correction at infinity is about +2.0.

Second, other than Florida springs, when does infinity mean anything as far as vision is concerned underwater.

So, second question, at what distance would one want to correct? My guess is that over ten feet is worthless.

Five feet? If anyone has answers, I'm about to order some lenses.

BTW, http://newportglass.com/aquidx.htm will make the lenses and ship them to you for you to install, up to bifocal lenses which are made by gluing the additional correction onto the main lens.

CompuDude
09-18-2007, 15:49
If you ever find yourself in good viz, that 200' vision might be worth having.

I'd give a call to www.prescriptiondivemasks.com and ask the optometrist who runs the place. They know everything you'll need to know, from both a diving perspective and a real optometry perspective.

RonFrank
09-18-2007, 16:49
These questions need to be answered by your doctor, and your lens manufacture.

Asking here may get you some answers, but since we are not optometrists, or lens manufactures, why would you want the opinion of folks who are not qualified, and worst, may GUESS and present things as fact! :smiley11:

The way this works is you get your prescription from the DOCTOR, and then you give that to the lens manufacture along with your mask specs. That is how it's been done by our fathers, and our forefathers throughout time. :smiley16:

emtmommy
09-19-2007, 09:02
Does anyone dive with the laser eye surgery?? Does it bother your eyes at a deep depth?

Dale
09-19-2007, 09:29
I suspect non-diving opticians and opthalmologists haven't a clue, which is why I asked here. I also suspect that near versus far focus is subjective and was hoping someone might know.

Lasik and Radial Keratotomy is done on extremely soft tissue with no blood supply. I'm no doctor nor an eye professional, so take with a grain of salt. I'm also an amateur astronomer and understand optics better than most.

Laser eye surgery has one side effect that can be annoying, that being diffraction spikes in an image. If you've ever seen pictures taken with a telescope that has the crossed spikes, it's caused by objects inside the telescope shaped similar to the spikes. Sports photos with donuts are from lenses with a small mirror in the middle of the front lens.

Likely not a problem underwater.

The cornea gets its O2 from the air around it, so diving should increase the O2 levels. It should diffuse quickly into and out of the cornea. I cannot imagine that Nitrogen levels would be a problem.

My purely amateur off the cuff opinion is that it should be a non-issue. Verify with a professional, though.

I don't do it because of two things. I require multiple prescriptions per eye and the diffraction spikes would diminish the enjoyment of astronomy.

CompuDude
09-19-2007, 12:25
I suspect non-diving opticians and opthalmologists haven't a clue, which is why I asked here.

That's why I referred you to the link I did. That company has lots of experience with the subject, from a diving and a medical point of view. They're very friendly on the phone, as well.

Dale
09-21-2007, 10:42
True enough, and I will call them. However, it's always good to hear from non-professionals with some hands on experience. In my diving experience in South Carolina, infinity was at about 2 1/2 feet :)

Some of my question isn't about the optics so much as it is about if you had to pick an area in clear water diving to see clearly, with everything else increasingly blurry the closer or further it gets, what is the most import point of focus for you?

I was hoping to find multiple points of view and reasons.

In a way, it is a bit like the question of "What is the best computer for me?" You can go talk to the computer nerds, but until you get a bunch of non-nerds to tell you what they like about theirs and why, you rally don't know whether you'd rather have 1920x1200 32 bit graphics or a 7.2 surround system.

CompuDude
09-21-2007, 12:49
Granted. It's true that the most important zone in diving vision is probably a 10-20' radius around you. But in areas with better vis, if you can't see well beyond that bubble, you can miss some really cool stuff... like spotting a bat ray feeding in the sand 40' away, and knowing to slow down and approach carefully so you can get an extended view, instead of not noticing it until you're right on top of it and scaring it off almost immediately... if you ever see it in the first place!

Dale
09-21-2007, 13:09
Harumph! It's not like as blind as a bat (ray) LOL!

I have been diving without correction and can see well enough to see what everyghing is. I'm probably just over borderline to drive sans glasses. Crystal Lens have really been looking good, but it's $5,000.

I guess that is part of the confusion. I've been using progressive lenses, so there is an area that I can always put into focus, everything else is just a little blurred.

For the lower lenses, I actually went to a drug store and held things about 18" away and found something that worked well. I can see gauges perfectly. No matter what diopter value I get between about +1.75 and +2.5, something is going to be sharp as a tack, the rest just a bit blurred.

Last time I went to get a prescription, I wanted special glasses for the computer. She asked me to hod something at the distance the screen was and we found something that worked. I can do the same thing at the drug store, if only I knew how far away, and it is such a subjective answer, I'm not sure anyone can know.


Granted. It's true that the most important zone in diving vision is probably a 10-20' radius around you. But in areas with better vis, if you can't see well beyond that bubble, you can miss some really cool stuff... like spotting a bat ray feeding in the sand 40' away, and knowing to slow down and approach carefully so you can get an extended view, instead of not noticing it until you're right on top of it and scaring it off almost immediately... if you ever see it in the first place!

Vercingetorix
09-21-2007, 13:33
I use bi-focals on land. In order to read my gages and SPG, I've installed a 3.0+ diopter lense in the lower part of my right dive lens. A pair costs $30 at ScubaToys. The lens is not "glued in". Rather, you get the dive mask lens wet and put the correction lens in. It sticks with water adhesion.

When I purchased a new mask, I filled the dive mask with water and the correction lens popped right off (with a fingernail) without damage to either the mask or lens.

Dale
09-21-2007, 14:38
Cool. This place will grind you a replacement lens for your mask and send it to you:

http://newportglass.com/aquidx.htm

BTW, I love the kid with the screwdriver. I think it might be a picture of me in first grade :)