Blurry vision underwater is due to pupil dilation, which can be controlled to see as if wearing mask

[CT-Rich]

I'm not saying that it can't be done. You can mess with lots of your stuff if you practice for years:
Most people won't have the patience to watch that vid for more than 30 sec. Nobody is going to practice for years when a stupidly simple fix exists.

Wow, when my cat does this, it usually follows that I am wiping up cat food or a hair ball with paper towels...

 

[lowviz]

But they have been practicing for countless years...

 

[DavBuc]

The video is completely bogus for a number of reasons.

The human iris cannot be trained to control miosis.

Even if it could the pinhole effect will not do anything for the blur due to the water/cornea interface, if anything it will further detract from the vision because of the loss of light.

My favorite part of the BS video was when they show everything coming into clear focus without any loss of brightness. Those kids aren't seeing any better than we would without a mask, they just "adapt to the blur" and use other methods to find their way around, just like the typical vision care patient who has vision loss but learns to cope with it.

As one gets closer to cataract surgery (outpatient and trivial procedure), the pinhole effect will be increasingly effective.

Wrong. As the lens within the eye gets cloudy, the person needs more light not less. The pinhole effect will only assist with blur due to refractive error not vision loss due to the cl

The eye has the cornea for the front lens and behind that whatever they call the lens that is replaced in cataract surgery. Behind that is the iris which controls the size of the pupil

You need an eye anatomy lesson.

I am now farsighted, and need blended trifocals to read easily.

There is no such thing as "blended trifocal lenses"

 

[CT-Rich]

Okay guys, this is about the weirdest thread I have ever seen on ScubaBoard. First, you cannot see more clearly with pupil dilation, because (as mentioned above) the depth-of-field is very shallow. You have more light-gathering ability, but reduced focus depth.

Second, while with a great amount of training, you may be able to dialate the pupils, why would you want to. It is precisely because this is reflexive, and not dependent on the mind's control, that we can seamlessly go from very dim light to bright light. But try to reverse that, and you'll find that it takes about 15 minutes to become fully dark adapted. This is because we have both rod and cone cells in our eyes for light perception. The rods are for night vision, and provide very good vision, once adapted, to the night. Cones are color-perception get cells, and function optimally in bright light.
Cone cell - Wikipedia

Third, there is this thing about our eyes being adapted to seeing in air, but not in water, due to the different refractive indexes of the two mediums. The only way that the human eye can see well underwater is to put an air barrier onto the eye; this means a mask or goggles must npbe used. If any other method was available, it would already have been invented. In my high school days, I undertook life guarding training. We learned how to see clearly without a mask or goggles when we had to float almost motionless for 15 minutes. Boredom overtook use, and we learned to use our hands to capture an air bubble around our eye socket/cupped hands and see clearly with our heads underwater. But again, in order for this to work, we needed an eye/air interface.

The idea that controlling eye dilitation can somehow overcome the physics of the eye/water refractive index change is bogus. Dilitation doesn't change this index, only makes the eye even less adapted to water by reducing the depth-of-field focus problems the eye experiences in the water. (The wider the pupil dialates, the narrower the depth of field; but the refractive index of the eye/water interface remains the same.)

The only way possible for the human eye to adapt is not to dialate the pupil, but to distort the eyeball itself; however I think the differences are such that such a distortion to change the focal distance would be rather painful and not something any of us would wish to do. Appropriate contact lenses have been developed and use daily underwater, but then you have the other problem of seeing out of the water.

SeaRat
John C. Ratliff, MSPH

This is the weirdest? I would say you just haven’t been paying attention.

The pinhole concept negates the need for a lens. The light entering the comes through a portion of the lens so small it is effectively flat. Your brain fixes a lot of the problems you have with light levels so things SEEM okay. My guess is that these kids see pretty well but would have trouble with specific tasks like color identification and things that have low contrast.

If you ever forget your glasses at a restaurant and want to read the menu, make your thumb and index finger into a tight opening and hold it to your eye. You will be amazed at text that would otherwise be unreadable.

Here is a video from a guy with way to much time on his hands explaining it

 

[DavBuc]

I attribute the fact that I have used the UV adjustable coating on all my glasses since that was an option for the fact that I still have my original, biological lenses in my eyes at this age.

SeaRat

Ok that's definitely a new one. "UV" adjustable coating. That one needs explaining, unless of course you mean photochromatic lenses that lighten and darken with exposure to varying levels of UV radiation.

And I stand by [some bogus video I found online]

Some people stand by the notion that the earth is flat. Your point?

Wow I didn't know that pupil dilation can be voluntarily controlled. That would help my dark-adapted vision after I got my eyes lazed.

LASIK vision correction does not, in ANY way affect dark adaption, it may however result in issues in low light conditions for various reasons including but not limited to residual corneal haze, epithelial defects, and dry eye symptoms which are usually worse at the end of the day.

Okay guys, this is about the weirdest thread I have ever seen on ScubaBoard. First, you cannot see more clearly with pupil dilation, because (as mentioned above) the depth-of-field is very shallow. You have more light-gathering ability, but reduced focus depth.

You make a lot of excellent points except for the fact that you use the word "dilation" when you should be using "contraction" or "constriction".

 

[Storker]

Digital and Photoshop killed the magic forever...

 

[lowviz]

...//... Wrong. As the lens within the eye gets cloudy, the person needs more light not less. The pinhole effect will only assist with blur due to refractive error ...//...

You have half the story with cloudiness, the ageing lens also distorts.

One can use a pinhole to search for a 'sweet spot'.

 

[DavBuc]

I'm now seeing 30/20, near and far..

Impossible.

 

[tursiops]

Impossible.

Why do you say that? I had an eye exam last week and that was the report I was given. Would you be more comfortable with 20/30? Maybe my eye lady is dyslexic. My point is, I am not wearing glasses near or far, but if I did, things would improve only a tiny bit.

 

[DavBuc]

You have half the story with cloudiness, the ageing lens also distorts.

One can use a pinhole to search for a 'sweet spot'.

Go ahead and read a few eye anatomy books, including some with pictures.

In order to get reasonably good vision, the light must be focused on the fovea, which is in the center of the macula, which is in the center of the retina. This entire structure only comprises a few degrees of central vision. The lens sits directly in front of, and in line with the fovea, so you cannot "find a sweet spot" that would make any difference unless it was DIRECTLY in line with the optical axis of the eyeball, and if that sweet spot WAS directly inline with the eyeball the vision would be as good as it would get without introducing a light decreasing device in front of the eye.