Author Topic: Relationship between Snellen Visual acuity and refractive state.  (Read 5768 times)

Offline OtisBrown

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #15 on: January 29, 2015, 06:54:55 PM »
Hi Hans,

Subject: What I care about, is always passing the  20/20 line, and making certain my refractive STATE is positive.

Hans> I do not say 20/10 is emmetropia. I do not care about the Snellen score.

Otis>  I always appreciate what you have to say, and think about your visual future.  We can all learn from your perspective.

Otis> If it were me, I would be interested in the following facts of science.

Otis> I know that in high school and college, the refractive state of all normal eyes goes down at a rate of -1/2 diopter per year.
People wearing a plus lens, DO NOT GO DOWN AT -1/2 DIOTPER PER YEAR.  In a relative sense, you are already down by
-1.5 diopters (by your own objective measurements).  Unless you are very lucky, you can expect to go down by about,
-3 diopters, (college and graduate school). You can add that to your current -1.5 diopters, for a total change of
-4.5 diopters.  At that point, you will be lucky to read the 20/200 line, with no glasses.  But since you
do not care about your visual acuity, that is no problem for you.

Otis>  I am an engineer, so I believe in science and facts - as presented here:

https://myopiafree.files.wordpress.com/2014/12/vis_6_17_p_pdf.pdf

Otis> For the wise, this is not a "scare tactic".  It is just the expected effect that long-term near
always has on the natural eye. 

Otis> If you want to use a different ''standard" for normal vision (20/20) and self-measured refractive states - that is of course
your business.

Otis> The ONLY difference, is what we call "zero" or measurement point.  I prefer the 20/20 line, you prefer the 20/10 line.  But we
have the same measurement goal.

Otis> But I do value my Snellen visual acuity.  I regret that you do not value your distant naked-eye vision - the way that I do, and
many other people do.

Otis> But then, I wonder what your interests are - if not to protect your distant vision for life.

Otis> I makes no difference to me, what you choose to do - because in the long-run, only you can care.

Hi Mr. Otis,

I do not say 20/10 is emmetropia. I do not care about the Snellen score. Emmetropia is - for me - that your edge of focus with +2 reading glasses is at 50 cm.

What the retina is able to do - that is another thing. And I do not say if you are nearsighted (-0.5 diopters and more) you have to wear glasses. Far-point measurements are very accurate to get your refractive state and not the 20/20 line.

The 20/20 line is a "guideline", but as I have said - with undercorrection, I can read further than 20/20. Do I have a positive refractive state? No, of course - I do not have. I can do better, but achieving this with a minus is DANGEROUS, while achieving it with naked eyes would be awesome.

Do you now understand what I mean?

Kind regards,
Hans
« Last Edit: January 29, 2015, 07:48:27 PM by OtisBrown »

Offline HansK

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #16 on: January 29, 2015, 08:01:44 PM »
Hi Mr. Otis,

you do not understand me. With my sentence "I do not care about the Snellen score", I meant the definition of emmetropia (physically). Of course - visual acuity is important. Additionally, I do not fight wearing a plus lens, where do you get that?

For instance: Mr. A's retina can resolve 20/15 and Mr. B's retina can resolve 20/10 (as someone is taller than another etc.).
-> 20/20 can be used as an average acuity, but saying that 20/20 is emmetropia is totally wrong.

Quote
If you want to use a different ''standard" for normal vision (20/20) and self-measured refractive states - that is of course your business.

Quote
The ONLY difference, is what we call "zero" or measurement point.  I prefer the 20/20 line, you prefer the 20/10 line.  But we have the same measurement goal.

I want to push the limits (not just in vision, but in other aspects, too: sports etc.), so I want to achieve "physical emmetropia". Being fully corrected, I can read 20/10 (other family members achieve that, too - but with their naked eyes).

Quote
I regret that you do not value your distant naked-eye vision - the way that I do, and many other people do.

Then I would not have stopped ortho-k, would I?

 I am honest - it is frustrating not wearing a minus lens (with my current visual acuity that fluctuates SIGNIFICANTLY). And if I have to (viewing graphs, reading on the blackboard etc.) and then looking around the room - we all know this feeling: "Why me?" and "Wow/Damn, I am missing the world/the details".

Kind regards,
Hans
« Last Edit: January 29, 2015, 08:11:55 PM by HansK »

Offline OtisBrown

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #17 on: January 29, 2015, 08:30:50 PM »
Hi Hans,

I do not think you understand me either, an my desire to have a personal measurement system, that makes sense to all of us.

I  understand this statement - PERFECTLY:

Hans> I am honest - it is frustrating not wearing a minus lens (with my current visual acuity that fluctuates SIGNIFICANTLY). And if I have to (viewing graphs, reading on the blackboard etc.) and then looking around the room - we all know this feeling: "Why me?" and "Wow/Damn, I am missing the world/the details".


Otis> That is exactly how I felt, when I found out that prevention was possible with a plus lens - worn almost all the time.

This is what "compels, the use of a strong minus lens.  The people who START wearing a strong minus, go down very rapidly.  It is like a drug, very addictive.  After some time - you can not stop wearing it.  When you go below 20/40, you will have no choice, but to wear it. 

Thus, when I state I have visual acuity of 20/20, I think you believe me.  When I state that I have a refractive STATE of
+1/2 diopter, then I measure RELATIVE to the 20/20 line. 

But you did not answer my questions about the statistics I posted.

If you wish to use some not-standard measuring system, then no one will object to what you are doing - as long
as you are clear about it.

In either measuring system, you must get a CHANGE of +1.5 diopters - I think we BOTH agree on that point.

I am also interest in how you judge that statistics I presented. 

1) Do you believe them?

2) Do you think your refraction is going to stay at -1.5 diopters (with 20/20) or do you think your refraction
will go down at a rate of -1/2 diopter per year.

3) Are you wearing a plus now - for all close work.


4) What other methods are you using, to get that +1.5 diopter change?

I am here to help you, not argue with you.  I think total commitment to wearing a
strong plus - though the school years, is indeed difficult - until you understand what
will happen to your refractive STATE, if you do not wear the plus intelligently.

But I am curious about how you judge these issues.

They will affect you, far more than they will ever affect me.



Hi Mr. Otis,

you do not understand me. With my sentence "I do not care about the Snellen score", I meant the definition of emmetropia (physically). Of course - visual acuity is important. Additionally, I do not fight wearing a plus lens, where do you get that?

For instance: Mr. A's retina can resolve 20/15 and Mr. B's retina can resolve 20/10 (as someone is taller than another etc.).
-> 20/20 can be used as an average acuity, but saying that 20/20 is emmetropia is totally wrong.

Quote
If you want to use a different ''standard" for normal vision (20/20) and self-measured refractive states - that is of course your business.

Quote
The ONLY difference, is what we call "zero" or measurement point.  I prefer the 20/20 line, you prefer the 20/10 line.  But we have the same measurement goal.

I want to push the limits (not just in vision, but in other aspects, too: sports etc.), so I want to achieve "physical emmetropia". Being fully corrected, I can read 20/10 (other family members achieve that, too - but with their naked eyes).

Quote
I regret that you do not value your distant naked-eye vision - the way that I do, and many other people do.

Then I would not have stopped ortho-k, would I?

 I am honest - it is frustrating not wearing a minus lens (with my current visual acuity that fluctuates SIGNIFICANTLY). And if I have to (viewing graphs, reading on the blackboard etc.) and then looking around the room - we all know this feeling: "Why me?" and "Wow/Damn, I am missing the world/the details".

Kind regards,
Hans
« Last Edit: January 29, 2015, 08:41:23 PM by OtisBrown »

Offline CapitalPrince

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #18 on: January 29, 2015, 09:53:20 PM »
Hi Hans,

for the classroom, either sit closer, or you can wear a minus that corrects your distance to perhaps 20/25-20/30, which may be a -0.25D or -0.5D.

This is why i suggest a bifocal, since having visual acuity less than 20/40 can be frustrating, and you feel like you are missing out.

20/20 is a good way to "define emmetropia" for this forum. If you really want "true emmetropic perfect vision". then you would have to read the 20/20 with a +1D. that would guarntee no blur whatsoever. And this is what the OD prescribes for.

vision fluctuates because you have no hyperopic reverse. I can feel my vision is worse in poor lighting and dim lighting also. if you can read the 20/20 with at least a +0.75D, that would mean non-fluctuating very sharp vision in all lighting

Offline HansK

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #19 on: January 29, 2015, 10:28:00 PM »
Hi Hans,

I do not think you understand me either, an my desire to have a personal measurement system, that makes sense to all of us.

I  understand this statement - PERFECTLY:

Hans> I am honest - it is frustrating not wearing a minus lens (with my current visual acuity that fluctuates SIGNIFICANTLY). And if I have to (viewing graphs, reading on the blackboard etc.) and then looking around the room - we all know this feeling: "Why me?" and "Wow/Damn, I am missing the world/the details".


Otis> That is exactly how I felt, when I found out that prevention was possible with a plus lens - worn almost all the time.

This is what "compels, the use of a strong minus lens.  The people who START wearing a strong minus, go down very rapidly.  It is like a drug, very addictive.  After some time - you can not stop wearing it.  When you go below 20/40, you will have no choice, but to wear it. 

Thus, when I state I have visual acuity of 20/20, I think you believe me.  When I state that I have a refractive STATE of
+1/2 diopter, then I measure RELATIVE to the 20/20 line. 

But you did not answer my questions about the statistics I posted.

If you wish to use some not-standard measuring system, then no one will object to what you are doing - as long
as you are clear about it.

In either measuring system, you must get a CHANGE of +1.5 diopters - I think we BOTH agree on that point.

I am also interest in how you judge that statistics I presented. 

1) Do you believe them?

2) Do you think your refraction is going to stay at -1.5 diopters (with 20/20) or do you think your refraction
will go down at a rate of -1/2 diopter per year.

3) Are you wearing a plus now - for all close work.


4) What other methods are you using, to get that +1.5 diopter change?

I am here to help you, not argue with you.  I think total commitment to wearing a
strong plus - though the school years, is indeed difficult - until you understand what
will happen to your refractive STATE, if you do not wear the plus intelligently.

But I am curious about how you judge these issues.

They will affect you, far more than they will ever affect me.



Hi Mr. Otis,

you do not understand me. With my sentence "I do not care about the Snellen score", I meant the definition of emmetropia (physically). Of course - visual acuity is important. Additionally, I do not fight wearing a plus lens, where do you get that?

For instance: Mr. A's retina can resolve 20/15 and Mr. B's retina can resolve 20/10 (as someone is taller than another etc.).
-> 20/20 can be used as an average acuity, but saying that 20/20 is emmetropia is totally wrong.

Quote
If you want to use a different ''standard" for normal vision (20/20) and self-measured refractive states - that is of course your business.

Quote
The ONLY difference, is what we call "zero" or measurement point.  I prefer the 20/20 line, you prefer the 20/10 line.  But we have the same measurement goal.

I want to push the limits (not just in vision, but in other aspects, too: sports etc.), so I want to achieve "physical emmetropia". Being fully corrected, I can read 20/10 (other family members achieve that, too - but with their naked eyes).

Quote
I regret that you do not value your distant naked-eye vision - the way that I do, and many other people do.

Then I would not have stopped ortho-k, would I?

 I am honest - it is frustrating not wearing a minus lens (with my current visual acuity that fluctuates SIGNIFICANTLY). And if I have to (viewing graphs, reading on the blackboard etc.) and then looking around the room - we all know this feeling: "Why me?" and "Wow/Damn, I am missing the world/the details".

Kind regards,
Hans

Hi Mr. Otis,

1) Yes, I do.
2) If I wear a (strong) minus lens (for close work), then yes (that is what I have experienced when I wore the strong minus for close work, too and after 4-6 weeks, my new prescription was about -1.50 diopters).
3) Yes, and I do the "print pushing" idea (edge of focus, with a slight blur). Sometimes, I can focus (no blur anymore) but when I blink, I lose the focus and the slight blur comes back.
4) I rarely wear a minus lens and try to handle with my (poor) acuity.

Kind regards,
Hans

Offline OtisBrown

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #20 on: January 30, 2015, 04:13:18 AM »

Hi Hans,

Hi Mr. Otis,

1) Yes, I do.
(Statistics, the eye that "does nothing" goes down at a rate of -1/2 diopter per year, for each year in school.  Plus group - does not go down.)

2) If I wear a (strong) minus lens (for close work), then yes (that is what I have experienced when I wore the strong minus for close work, too and after 4-6 weeks, my new prescription was about -1.50 diopters).
(Good. This is of course most difficult.  It proves my point about, "Over-prescription", of giving a person a -1.5 diopter lens, when they can read the 20/20 line.
This is why I ask a person to read their own bright Snellen, so they can avoid wearing a strong minus lens - when they objectively have 20/25 to 20/20 vision  The optometrist ASSUMES that you only "understand" a strong minus - so there is no discussion of self-checking and, with 20/20, avoiding the minus legally.)

3) Yes, and I do the "print pushing" idea (edge of focus, with a slight blur). Sometimes, I can focus (no blur anymore) but when I blink, I lose the focus and the slight blur comes back.
(For you, that means you probably can read through a +2.5 diopter, for all close work.  For people at 20/30, they can probably only wear a +1.5 D, initially.)

4) I rarely wear a minus lens and try to handle with my (poor) acuity.
(With respect, an interesting statement.  I personally confirm my vision at objective 20/20.  I do not consider this to be "poor acuity", since it is normal visual acuity.  But that is the basis of our discussion.

For myself,  I wish I had had all of the above information, when I was at 20/40, and -1 diopter.  I know that no OD will SUPPLY this information, because it takes so much intelligence to understand it.  The "plus" data does prove one point - that to retain or keep your distant vision though the school years.

It is very clear that no optometrist can help you with any of this - and I do not hold the OD as responsible.  With the above information, properly understood,
I hold myself responsible.

But prevention must be a choice, while you can still read the 20/40 line, and few people have that type of self-motivation.

Sincerely,




Offline HansK

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #21 on: January 30, 2015, 05:30:00 AM »
Hi Mr. Otis,

20/30 is not consistent - I rarely achieve it (when I check my Snellen in daylight), and if - it does not last that long.

I am between 20/50 to 20/40 consistently, sometimes 20/60 in poor conditions (in the evening, no brightly-lit Snellen).

Kind regards,
Hans

Offline OtisBrown

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #22 on: January 30, 2015, 06:34:38 AM »
Hi Hans,

Since you are in high school, and have accurately (judged) your visual acuity, consistently, you know what you are doing.

I also  hope you obtained some "test lenses" from Zennioptical, of -1 and -1.5 diopters, again for self checking of your refractive STATE.

It should be clear, from our conversations, that it is totally impossible for an optometrist to be of any help to you.  In other words, this
is not medicine, and prevention is not medical - at all.

(I previously thought you said that you had 20/20 vision - thanks for correcting me on that point.)

I now estimate your refraction (based on your visual acuity) to be about -1.0 diopters, relative to the 20/20 line.  This is why I
use my own trial-lens, to determine the amount of minus it takes to "just clear" the 20/20 line, under my personal control.

WITH RESPECT TO  THOSE STATISTICS.

https://myopiafree.files.wordpress.com/2014/12/vis_6_17_p_pdf.pdf

They do paint a "bleak" future, if you start wearing a strong minus, 24/7.  In fact, I will not go "against" these statistics,
and make claims of "recovery". 

You have gone "down" by about -1 diopters, in the last three years, based on your own measurements.

We know that "school living" and reading (with no plus) is responsible for this "change in refractive state".

I do not "sell" a plus, and the plus is not "medical".  No one medical can help you - but perhaps you can help yourself.

You are in a position, to "reverse" that refractive state - but we all admit to this truth -- IT IS A VERY SLOW PROCESS.

There are people who DEMAND that optometrists SOLVE THIS PROBLEM.  That is totally impossible, and I think
you understand why it is impossible.

I know that, unless specifically educated, most people will HATE wearing a plus - for the long-years you will be in school.

I do not have any "answer" fo that issue - except that science shows that there is little choice.  Neglect - which
most people will choose, simply means your vision keeps on going down - at that -1/2 diopter per year.

That is now the issue - for you.  I consider that people at 20/30, have an "either or " choice, given the final
statistics I posted.  I truly do not think people can "face"  those statistics, and take necessary preventive
measure - which means - long-term wearing of a plus for all "near" work.

I am not going to judge you, or the choice you will be making over the next six years (high school, college, Grad school),
but I think you understand a choice that you will be making (and none of us, here, will ever know your results).

That is how it should be (as fundamental science).

I do not know what "path in life" you will choose - and I can not "control that".

But you have a scientific education, and know that your choice - has consequences - that only you can control.


Hi Mr. Otis,

20/30 is not consistent - I rarely achieve it (when I check my Snellen in daylight), and if - it does not last that long.

I am between 20/50 to 20/40 consistently, sometimes 20/60 in poor conditions (in the evening, no brightly-lit Snellen).

Kind regards,
Hans
« Last Edit: January 30, 2015, 06:43:29 AM by OtisBrown »

Offline CapitalPrince

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Re: Relationship between Snellen Visual acuity and refractive state.
« Reply #23 on: January 30, 2015, 07:03:46 AM »
Hans,

get a -0.25D/+1.75D bifocal. you seem to be frustrated at having 20/40-20/50 vision

good luck.