Re: [Phys-L] cataract lens replacement

[Bill Norwood <bnorwood111@gmail.com>]

Kyle,
- William F. Bates (1860-1931) discovered, I guess in the 1920's or 1930's,
that some of our focusing comes from elongation and anti-elongation of the
eyeball.
- He was an eye surgeon.
- He was dismissed as a quack back then because he was teaching that
exercising the eyes could either rid one of the need for glasses, or arrest
the typical escalating of lens prescription as the decades roll by. Bad for
business.
- A Bates history,   http://www.visionsofjoy.org/AboutBates.htm
- Right now I am reading "How the Brain Heals Itself," and in that new book
Norman Doidge, MD tells of an intriguing professionalism on the part of
Bates. I was so surprised to find that information, since the ONLY info I
had seen on Bates had been from when I read his book, Better Eyesight
Without Glasses, several decades ago.
- It would be a revelation for me indeed if Bates' discovery could explain
modern day contact lens focusing.
Bill Norwood, Physics Dept, U of MD at College Park

On Thu, Dec 1, 2016 at 12:20 PM, Forinash III, Kyle <kforinas@ius.edu>
wrote:

> Does anyone know much about cataract lens replacements? (I was surprised I
> could not find anything in a search of Phys-L archives).
>
> I have one new lens at present (the other eye next week) and have two
> questions.
>
> 1. How can a single tiny lens have more than one focal length? My new lens
> allows me to see distance objects clearly and also objects close up (this
> was an added expense over and above the usual distance lens they typically
> use). I believe (based on the tech person who scheduled the surgery) it is
> a fresnel type lens but I don’t know much else. The angle I look at things
> doesn’t seem to matter (so I don’t think it is like a graduated bifocal
> lens).
>
> 2. Why would an insertion at a slight angle work to resolve astigmatism? I
> would have thought the lens would be circularly symmetric so the angle at
> which it was inserted should not matter but they tell me they were able to
> correct about half my mild astigmatism by inserting at 60 degrees (about 2
> o’clock when looking from the front). There are asthmatic lens replacements
> but I did not get that kind of lens.
>
> kyle
>
> -------------------------------
> "In science "fact" can only mean confirmed to such a degree that it would
> be perverse to withhold provisional assent."
>    - Steven J. Gould
>
>  kyle forinash
>   kforinas@ius.edu
> http://pages.iu.edu/~kforinas/
>
>
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