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

[DavBuc]

The first 3.8 million of our evolution we lacked UV absorbing glasses and corrective lenses. I think I wil avoid bursting into flames if left in direct sunlight.

Well, no, you won't burst into flames if left in direct sunlight, and neither did our ancestors, however we have a lot more knowledge than they did, which gives us the power to improve our lives and protect our health. It's been proven that sunlight causes cataracts and sometimes irreversible retinal degeneration, so avoiding direct sunlight can and in many cases does avoid vision loss. I think I'd rather burst into flames at age 60 than live to age 80 but be blind the last 20 years of my life. Your mileage may vary.

 

[tarponchik]

You may not "see" a difference but for the vast majority of the population, over the counter magnifiers are not nearly as effective as rx reading glasses.

Here's the reasons

1- most people do not have exactly the same refraction between their two eyes, so for maximal visual efficiency the lenses in their eyeglasses need to be 2 different strengths. Try it yourself, look at a distant object. Cover- not close- one eye, then the other. Feel free to repeat. Are the objects in exactly the same focus? If so you're one of the lucky few, if not, perhaps you see my point.

2- Many people have astigmatism, which is an "out of roundness" of the cornea, and/or a tilt of the intraocular lens, either of which add a component to a real eyeglass Rx that is not present in OTC magnifiers and enhances the vision.

3- Optics in OTC mags are not of the same quality as Rx Nvs which can cause further vision degradation and distortion.

4- The eyeglass frames are of cheap material and cannot be adjusted properly.

5- Any sort of reading glasses whether it's an OTC magnifier or RX reading glass is not going to give the depth of focus that a progressive multifocal can provide, which becomes more important as we age and our intraocular lens loses flexibility, and after cataract surgery when the intraocular lens has been replace with a rigid silicon lens- although there have been advances in technology and focusable intraocular lens replacements are now available.

I do have astigmatism, actually. But still I can't tell (I guess, "tell" is a better word than "see" here) the difference. Probably, because I got used to. It is the difference between 99% and 97%. And since the comp screen or a book page are flat, I do not need any depth of field when I have these glasses on. Think of it as Rolex vs. Timex. I am sure there are multiple reasons why the former's price is $1,500 while the latter is worth around $50, but both would tell me it is 1:44 pm now. So I won't be able to tell the difference.

 

[gcarter]

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

When I cannot read a menu due to some combination of low light and small print, or if I am wanting to read the small print on something while shopping, I take a picture with my cellphone and zoom in. Works like a charm

 

[DavBuc]

I do have astigmatism, actually. But still I can't tell (I guess, "tell" is a better word than "see" here) the difference. Probably, because I got used to. It is the difference between 99% and 97%. And since the comp screen or a book page are flat, I do not need any depth of field when I have these glasses on. Think of it as Rolex vs. Timex. I am sure there are multiple reasons why the former's price is $1,500 while the latter is worth around $50, but both would tell me it is 1:44 pm now. So I won't be able to tell the difference.

Loss of depth of field and focus as we age due to presbyopia (increasing rigidity of the intraocular lens) doesn't have all that much to do with whether you hold a book flat or tilted- it does make "some" difference but where it really matters is when you spend a lot of time doing visual tasks at distances that vary by, say 6" to 2'. The obvious example being sitting at a desk where you've got reading material at 16-18" but the computer monitor is 20-24" away.

 

[tarponchik]

Loss of depth of field and focus as we age due to presbyopia (increasing rigidity of the intraocular lens) doesn't have all that much to do with whether you hold a book flat or tilted- it does make "some" difference but where it really matters is when you spend a lot of time doing visual tasks at distances that vary by, say 6" to 2'. The obvious example being sitting at a desk where you've got reading material at 16-18" but the computer monitor is 20-24" away.

I know, but I replied to your different point, that cheap reading glasses do not provide depth of field. The best way to preserve you vision is to perform tasks that involve alternating focusing at things that are close and far, like driving a car, of course, but we have to spend some time reading etc.

 

[DavBuc]

I know, but I replied to your different point, that cheap reading glasses do not provide depth of field. The best way to preserve you vision is to perform tasks that involve alternating focusing at things that are close and far, like driving a car, of course, but we have to spend some time reading etc.

What I said was cheap reading glasses and rx reading glasses do not provide the depth of field available with multifocals.

Performing tasks that involve alternate focusing on things that are close and far do NOT "preserve vision". The loss of focusing ability as we age, known as presbyopia, is due to the increasing rigidity of the eye's crystalline lens and there is no way to prevent this process nor slow it down.

 

[CT-Rich]

Glasses don’t affect depth of field. The lens on your glasses provide a focal distance to correct for what lens in your eye cannot do on their own. Multi focal lenses have areas of the lens that correct your eyes at different distances.

Cheap reading glasses will do the job. It’s in the details that you see a difference. Dime store glasses will cause eye strain, because they make your eyes work harder than they would with glasses custom made for you.

 

[DavBuc]

The lens on your glasses provide a focal distance to correct for what lens in your eye cannot do on its own.

Most of your post is correct, I'll only comment on the error.

The lens only provides a small percentage of the refractive power of the human eyeball.

Most of it is due to the cornea.

 

[Texasguy]

My god, I just checked in, what have you done with my beautiful thread?!?

 

[DavBuc]

My god, I just checked in, what have you done with my beautiful thread?!?

We debunked it.