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undidly
2010-Mar-26, 01:15 PM
I am becoming annoyed by what seems to me to be a stupid explanation for
short sightedness.
I think we all agree that the sighted image is in front of the retina instead
of ON the retina.
Some experts say this is because the eyeball is too long ,that is why the focus point is before the retina and show a cross section of an elliptical eyeball,elongated front to back.
How can such an eyeball turn in its socket?.

The fault is in the lens which is too curved ,caused by much viewing of close
things.The lens takes a shape suited to the most common use.
The word wide increase in short sightedness in children can be cured if they
wear reading glasses every time they read.The lens will not need to curve
beyond that needed for normal vision.

So ,how is the elliptical eye ball supported in a spherical socket?.
In an elliptical socket it cannot turn.

Strange
2010-Mar-26, 01:29 PM
I'm quite sure the eyeball is not perfectly spherical. I'm also sure that the diagrams you have seen greatly exaggerate the eccentricity. The eyball is quite "squishy" (technical term) so being slightly elliptical would not cause any rotation difficulties - it doesn't move that much anyway.

An interesting experiment could be to see if the degree of shortsightedness changes if you turn your eye as far as possible to the side (thus, potentially, increasing the pressure on it and changing the shape).

I don't know if there have been any studies of the amount of time spent reading and incidence of shortsightedness. Or, alternatively, the genetic component (it seems to run in families). I certainly spent nearly all my youth reading and never needed glasses until recently - and that is purely age-related - loss of flexibility in the lens.

Call me old fashioned, but I tend to go with the experts unless there is some convincing evidence to the contrary.

I also can't see kids being persuaded to wear "preventative" glasses just in case they become short sighted. As the biggest problem with shortsightedness is having to wear glasses, it doesn't seem that wearing glasses to prevent it is much of a benefit. ;)

Kaptain K
2010-Mar-26, 02:58 PM
I have worn glasses since I was 5 (before I could read)! So much for your theory that reading causes myopia.

NEOWatcher
2010-Mar-26, 04:08 PM
I consider myself to be nearsighted and not shortsighted. ;)

There must be some regional differences in what it's called.

rommel543
2010-Mar-26, 04:10 PM
The way that it was explained to me when I needed to get glasses 10 years ago was that it from repetitively straining your eyes in the same manner over and over again, like working on a computer. The eye, like Strange mentioned, is squishy and deforms when the muscles around your eye contract/relax to allow to to focus. Now just like a body builder, if you do the same exercises (or in this case same type of strain on your eye) the muscles become 'muscle bound' and can't fully contract o relax anymore. Because of this muscle bound state you eye is not deformed in that shape as well. So if you are constantly looking at a computer screen, or having to read small lettering close up, your eyes will get 'reformed' from the constant eye strain of looking at something that close to your face. Thats why it's suggested that you look around every so often when reading/doing computer work/video games/etc, so your eyes have the chance to 'stretch it's muscles' and avoid the eye strain and deforming.

DonM435
2010-Mar-26, 04:54 PM
Wouldn't the eyeball respond slightly to gravity, and hence get longer when you were looking straight up? Maybe that would explain why some people can discern double stars that seem to be too close for the alleged limits of human vision? Or would that make distant vision worse?

undidly
2010-Mar-27, 12:18 AM
The way that it was explained to me when I needed to get glasses 10 years ago was that it from repetitively straining your eyes in the same manner over and over again, like working on a computer. The eye, like Strange mentioned, is squishy and deforms when the muscles around your eye contract/relax to allow to to focus. Now just like a body builder, if you do the same exercises (or in this case same type of strain on your eye) the muscles become 'muscle bound' and can't fully contract o relax anymore. Because of this muscle bound state you eye is not deformed in that shape as well. So if you are constantly looking at a computer screen, or having to read small lettering close up, your eyes will get 'reformed' from the constant eye strain of looking at something that close to your face. Thats why it's suggested that you look around every so often when reading/doing computer work/video games/etc, so your eyes have the chance to 'stretch it's muscles' and avoid the eye strain and deforming.

That is what I said.
Wearing reading glasses for ALL close up work means that the lens never has to deform itself to the extreme so is unlikely to be permanently wrong for
long distance.
""is squishy and deforms when""
The eyeball is not squishy.It has its own internal pressure to ensure that it is ALWAYS spherical.
Focusing is done in the lens and not by distorting the entire eyeball.

Trebuchet
2010-Mar-27, 03:19 AM
I've had glasses for nearsightedness since I was about 14. I also heard that it was due to the amount I read (a lot) but never really believed it.

The interesting thing is that now that I'm older and presbyopia has set in, my unaided vision is better than it's been since I was 16 or so. I can see well out to around three feet away (used to be more like three inches) and routinely read without my glasses. I'd probably even dare to drive that way in an emergency.