Author Topic: how the eyes adapt  (Read 3011 times)

Offline RynEyes

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how the eyes adapt
« on: March 14, 2015, 07:41:02 PM »
By what mechanism does the eye eventually adapt to be able to focus on something further beyond the focal point of a given plus lens?  For instance, a +1.5 lens has a focal point of 0.66 meters.  What happens in the eye that allows you to focus on things farther and farther from that distance?

Offline jimboston

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Re: how the eyes adapt
« Reply #1 on: March 17, 2015, 05:15:44 AM »
You asked the million dollar question. Conventional ophthalmologists don't believe refractive errors can be improved. Rehabilitation is controversial and there are good reasons to be skeptical.

Offline rtdfgdfgdfgdfg

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Re: how the eyes adapt
« Reply #2 on: March 17, 2015, 06:08:10 AM »
Let's say you have perfect eyesight.

You are prescribed, wrongly, glasses for -2 in each eye.

Will the eye change and adapt to the glasses to produce 20/20 vision ?

and can the eye adapt to a plus lens ?
« Last Edit: March 17, 2015, 06:14:09 AM by rtdfgdfgdfgdfg »

Offline OtisBrown

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Re: how the eyes adapt
« Reply #3 on: March 17, 2015, 08:30:23 AM »
Hi Rtd....,

ISSUE:  That was indeed, *my* question of a long time ago.  But you must define precisely what you mean by "perfect, normal eye".

I will define it as an eye with a refractive STATE of exactly zero, (both eyes).  The method of measurement is to put
up a Snellen chart, and test to see if a "plus or minus", "just blurs vision."

So your scientific question is this -- will the natural eye change its refractive state by -1.0 diopters, in say nine months, of full time wear?
(As a qualifying, scientific test - that will satisfy your scientific interest for an objective scientific test?)

Do you want the scientific answer, as established by objective testing?  Or do you want the optometrist's answer, he will give you in his office?

(I KNOW the optometrist answer - maybe you can guess what they will tell you.)

I certainly agree that the correct, objective SCIENTIFIC answer, will not be an answer you will "like" or enjoy.  This has nothing to do
with cure, or any "search for a cure".

Please let me emphasize that asking, and answering, correctly, is never a medical issue.

This is this tough scientific question, and implies no dis-respect to anyone who is medical.


Let's say you have perfect eyesight.

You are prescribed, wrongly, glasses for -2 in each eye.

Will the eye change and adapt to the glasses to produce 20/20 vision ?

and can the eye adapt to a plus lens ?
« Last Edit: March 17, 2015, 04:04:41 PM by OtisBrown »

Offline Alex_Myopic

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Offline rtdfgdfgdfgdfg

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Re: how the eyes adapt
« Reply #5 on: March 17, 2015, 04:14:18 PM »
to clarify

I would like the  scientific answer, as established by objective testing

of whether the eye adjusts to the lens

Offline OtisBrown

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Re: how the eyes adapt
« Reply #6 on: March 17, 2015, 07:21:47 PM »
Hi Rtd....,

The answer depends on who you think did the scientific test, and that you define exactly what you are looking for in a
pure scientific test.

I personally look for the natural eye to change its objective refractive STATE in BOTH DIRECTIONS.  You will find the
scientific results, under "Graphics". 

 If the natural eye did not always do this, under controlled objective testing,'
and this were not a REPEATABLE scientific test, I simply would not post here.


https://myopiafree.wordpress.com/graphics/

But if you want a "medical" explanation, then this is not an objective medical test - according to the medical community.

You have a right to be informed of this science.  You also have the right  to totally ignore it, and follow the
advice of your optometrist.

to clarify

I would like the  scientific answer, as established by objective testing

of whether the eye adjusts to the lens
« Last Edit: March 18, 2015, 03:33:21 AM by OtisBrown »

Offline RynEyes

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Re: how the eyes adapt
« Reply #7 on: March 18, 2015, 06:20:55 AM »
So lets say one begins to use a plus lens for reading.  Initially the lens power is chosen such that the text appears slightly blurred.

My understanding is that as the light bounces off the reading material, it passes through the plus lens, then the lens of the eye, and then focuses somewhere near the back of the retina. If the light rays focus directly on the retina, the image is crystal clear, otherwise, it is blurred; a plus lens focuses the light in front of the retina, and a minus behind.  Is this an accurate understanding?

After some time of using the plus lens, say several  months, the image is now crystal clear at that distance.  Is the current theory that this occurred as a result of the eye adapting (in essence shortening so that the back of the retina has been brought forward such that it is now at the focal point of the light)?

Offline jimboston

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Re: how the eyes adapt
« Reply #8 on: March 18, 2015, 08:30:06 AM »
RynEyes,

You can check my post history for debates on the topic, but so far no one has been able to prove scientifically that the retina adapts to slight blur by moving in a particular direction. The keyword you are looking for is axial length (AL). Increased AL is the main reason for myopia, and 1h and 1-day studies on myopic defocus on humans have failed to show that AL can be permanently changed.

Those studies showed that AL does get shorter after an hour or more of using plus lenses, however, the effects were very small and were completely erased after sleep. The rehab community operates on the assumption that consistent, prolonged use of myopic defocus can eventually lead to a permanent AL change. Since none of those who claimed improvement tried or wanted to take AL measures before and after their rehabilitation, their claims that AL has permanently changed have been so far unsubstantiated.

Unfortuntely, my personal experiments as well as those of a few others who have recently posted on this forum state zero improvement after 6 months of slight blur. This means:

a) there is a mysterious trick none of us is able to replicate, or
b) the process is very, very slow even with hours of edge of blur work, or
c) the method simply doesn't work

You can check warnbd's journey as well. He claims he had a several diopter improvement with these techniques. He hasn't taken AL measurements, however.
« Last Edit: March 18, 2015, 08:34:46 AM by jimboston »

Offline rtdfgdfgdfgdfg

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Re: how the eyes adapt
« Reply #9 on: March 18, 2015, 08:47:42 AM »
https://myopiafree.wordpress.com/graphics/



[/quote]

Thank you.

But I must admit, those graphics are very hard to understand.

What was the eyesight before ?
What was it after ?
Were they a plus lens ?
Or a minus lens ?

Maybe I am just inept at reading charts

Off topic - why do people with multiple personality disorder need glasses, but another personality doesn't ?

Personally, print pushing did not work for me.
« Last Edit: March 18, 2015, 08:55:14 AM by rtdfgdfgdfgdfg »