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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


B. -9.00 .... 20/1000
I have no experience here other than my simulation. I did wear one +3.5 glasses over my -5 eye to simulate -8.5 and was seeing 16/800 which is basically 20/1000 and compenstating for magnification, its 20/1070 at -8.5 and a solid 20/30 BCVA. I tried again and came up with 20/1140 this time compenstating for magnification and all and 15/800 which I could see clear enough for 80-90% accuracy. I am just going to say I very highly doubt anyones gonna be seeing 20/800 with -9 and in fact its safe to say youd be perhaps 20/1200, definately no better than 20/1000! I am stopping here as its moot offering baseless explanations for higher than -9. You may see the 20/xxx for higher in my first post but its based only on my formula and I honestly dont know if the formula is this linear. You can clearly see the pattern where each 1.5x increase in myopia results in a .5x accuracy. This formula starts at 20/100 and keeps going on. Does it end somewhere before that? At 20/400? 20/600? 20/800? Whats the new formula after this, on what expotentional scale?
12/23/2005, 3:34 pm Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


The above post(about the -9) is a countinuation from the bottom post on page 3. I will be adding more case examples and my comments:

Case example 1: My eyesight is 20/400 -5.25 diopter with a slight astigmatism (pretty dadgum bad).

My comment: This just barely agrees with my diopter chart. However with the astigmastim factored in, he would need to perhaps be 20/15 BCVA to just barely pass 20/400 uncorrected with this pescription.


Case example 2: I made the 20/20 cut but by my NAMI physical in Pensacola the next year, I was at 20/30 (probably stressed a bit as well). Luckily the cut was then 20/30 correctable to 20/20. From 93 to about 00, my eyes slowly became worse until they bottomed out at 20/80 (-2.00 as I recall). I then had PRK in 03 and my eyes have been perfect sense. I've got 20/12.5 vision in both eyes

My comment: I would think hed be seeing closer to 20/60 if he could be corrected better than 20/20 with glasses and with PRK. I bet he must of had a little astigmastim or perhaps been closer to -2.5 but didnt exactly remember. However -2 and 20/80 does agree with my diopter chart for 20/20 BCVA


Case example 3: I have an issue with astigmatism -4.75 my vision is 20/50 both eyes.

My comment: That would be near -2.5 diopters spherical equivalent. I highly doubt someone with this much astigmastim can see 20/50 Perhaps his other eye is less astigmatic since he mentioned both eyes so the 20/50 is the better eye doing the work?

Case example 4: It's hard for me to believe that you can read the 20/40 line with an astigmatism or -4.00. you are correct in the fact that because my astigmatism is what it is my vision should be alot worse than what it is, this is the same reply that I have received from so many docters.

My comment: Again this is hard to believe. Thats a spherical equivalent of -2 myopia


Case example 5: Anyway, my eyes were 20/400 and -4.75 diopters in both eyes before the surgery.

My comment: Makes perfect sense. I am -4.5 in the right eye and can just barely see 20/400, the left at -5 cant.

Case example 6: I want to apply for SNA but my uncorrected vision is 20/400 and -4.75 diopters.

My comment: same as above. Another example.

Case example 7: I had it done in September, my vision was 20/400, (-4.5 diopters).

My comment: pretty much the same as the two above. I do believe he may have just barely been able to see 20/300 if there was a 20/300 line on the snellen chart he was being tested on.

Case example 8: I am not sure what the 20/xxx was before surgery, I just know that I was -7.25 and -6.5. I'm sure its somewhere around 20/600 or worse

My comment: This makes sense. Accroding to my diopter chart, he would have a hard time seeing 20/600 in the better eye and his worse eye would likley be closer to 20/800. Sucks being a high myope.

Case example 9: Diopters are now -4.00 and -3.25. About 20/200 uncorrected, but I correct to 20/20.

My comment: This sounds right for the -3.25 eye. I doubt his -4 eye is going to be able to see 20/200. With both eyes of course he can see 20/200 because the better eye will be doing the work.

Case example 10: +/- 8 is greater then 20/100... and i'm -3 and i'm WAY past 20/100 and got in.

My comment: This makes sense. Not too many people will see 20/100 at -3. This pescription is generally accepted to be closer to 20/200.


Case example 11: I had -1.75 with an astigmatism, that gave me around 20/45 vision, had PRK, now I see alittle better than 20/15

My comment: Since hes correctable to at least 20/15, his visual accuracy is in line with his pescription.


Case example 12: Ok I had a 1.25 diopter in left eye with 20/80 vision, and just under 1 diopter in right eye with 20/40. granted my eyes were not that bad i got the surgery with 20/15 results

My comment: He must of had some astigmastim as well, especially in the left eye. An extra 1/4 diopter myopia is NOT going to take you down to 20/80 from 20/40


Case example 13: Some more details for those interested: My refractive error was measured at MEPS as -4.00/-4.25 (left/right eye) and during my flight physical as -4.00/-4.00. My distant uncorrected vision was 20/400 (i.e., I couldn't read the 20/200 line). With glasses, I correct to 20/20.

My comment: If his eyechart had a 20/300 line he would definately see that. I am not supprised he cant see 20/200, but perhaps he could if he was correctable to 20/15

Case example 14: The astigmatism is now -1.00 in the L, and -1.50 in the right. I was
told as the AK's gradually settle further over the next several months I
can expect further minor improvement. ) Snellen acuity for L is 20/20-
(just short of 20/20, and I don't understand this), and the R is 20/25 and
is more likely to improve further.

My comment: With his mild astigmastim, it makes sense hes 20/25, the left being better obviously due to less astigmastim.

Case example 15: at -1.5 diopters
and 20/60, get to 20/20 by
looking through a negative lens

My comment: Makes perfect sense accroding to my diopter chart. This is right on!

Case example 16: I'm not familiar with prescriptions other than I have -6.00 (yup...20/500 over here).

My comment: This one also makes perfect sense. With this pescription, he would barely see 20/500. Since most eyecharts dont have a 20/500 line, he could be considered 20/600.

Case example 17: I'm no eye doc, but -3.50/-4.25 is WAY worse than 20/40. My contacts are -2.00 and my vision is ~20/100.

My comment: Thats correct. I would be considering him 20/200 to 20/300 with his pescription, the better eye being barely 20/200 and the worse eye at 20/300. As to the -2 contact lense guy, thats equal to -2.5 glasses unless hes being overcorrected with his contacts. This does correspond to 20/100 or therebouts.

Case example 18: My vision is approximately 20/75 My diopter measurements are -2.25

My comment: Not a bad acuracy for this diopters. Never seen a 20/75 line, so well say hes 20/70. Hes probably correctable to 20/15 in order to be 20/70 at -2.25

Case example 19: Ace, I looked at my last pair of prescription contacts and they read a -2.00 prescription. Does this make more sense regarding my 20/80 distance vision without glasses? I correct to 20/15

My comment: Due to vertex distance, he should be a -2.5 in glasses. His example concides perfectly with my diopter chart. 20/15 BCVA, 20/80 at -2.5(20/80 at -2 if 20/20 BCVA)

Case example 20: I requested to be left slightly myopic to keep me out of readers till my late 40s. My distant vision is 20/20 in normal lighting, but drops to about 20/30 in dim light. So I keep a pair of -0.75 specs in the car that I use only rarely during night driving

My comment: This concides perfectly with my diopter chart. The 20/20 is due to pinhole effect or correction at -.75 diopters.


Case example 21:
I have begun CRT about 1 week ago. Here is my data: Initial refraction -3.50-1.50x010 OD, -4.50-1.00x170 OS.
After 1 week overnight wear I am -0.25-0.50x180 OD, -0.25DS OD with
20/20 OD, 20/20 OS uncorrected.

My comment: -.25 diopters may make the 20/20 line a little blurry but this is so little "myopia" it should not cost any lines. One optometrist even stated that hes never had a patient lose a line with a -.25 refractive error.

Case example 22: I am a 28 years age and 10 years ago I underwent Ortho-K treatment.
Back then I had 20/60 vision in both eyes. My optometrist promised me
at least 20/20. I got it. However, 10 years later, I now have 20/160
with -2.25 in both eyes.

My comment: This is below the 20/100 he "should" see but perhaps he has a bit of astigmastim or isnt fully correctable to 20/20 but can see some of it.

Case example 23: Following cataract surgery in the OS, I have 20/40 vision in that eye
although it can be improved to 20/20 with a -1D lens.

My comment: makes perfect sense. -1 reduces his vision by half

Case example 24: Actually my prescription is -3.00 about in each eye. At twenty feet
the OD says I can only see 20/160, 20/200. After resting I could probably see about 20/100, or 20/70 or so.

My comment: A -3 refractive error does correlate to 20/150 on my diopter chart but some charts have 20/160 instead. Close enough I guess and I bet he could easily see 20/150 if not better with a little resting like he stated.

Case example 25: 2/27/98: I had my one month exam yesterday. My left eye is still
plano. My right eye has 1/2 diopter myopia with approximately 1/2
diopter astigmatism. My co-managing doctor told me I have 20/25
vision <grin>.

My comment: Makes sense. Half diopter reduces your BCVA by one line.


Ok thats it for 25 cases. I may update with more cases in a new post. Below presents my summary:









Last edited by Myope5, 1/5/2006, 3:56 am
12/24/2005, 7:30 am Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Countinued from post above


Ok thats it for 25 cases. I may update with more cases in a new post. Below presents my summary which is reprensative for nearly everyone correctable to 20/20.


diopters to 20/something

less than -1........20/20 to 20/30
-1........20/30 to 20/40
-1.5........20/40 to 20/70
-2........20/70 to 20/100
-2.5........20/100 to 20/150
-3........20/150 to 20/200
-4........20/200 to 20/300
-5........20/400


20/something to diopters

20/30........less than -1
20/40........-1 to -1.25
20/50........-1.25 to -1.5
20/70........-1.5 to -2
20/100........-2 to -2.5
20/150........-2.5 to -3.25
20/200........-3.25 to -4
20/300........-4 to -4.75
20/400........-4.75 to -5.5

20/something representating dioptric range extremes, this takes into account BCVA no worse than 20/25 and as good as 20/10 or even better!

20/25........plano to -1.75
20/30........-.25 to -2.25
20/40........-.5 to -2.5
20/50........-.75 to -3
20/70........-1 to -3.5
20/100........-1.5 to -4

I am not exactly sure on the upper end extremes because BCVA of 20/10 or even better is very, very rare(less than 2% get 20/10). I have heard claims of 20/20 with -1 a few times however. They were correctable better than 20/15 of course. Then theres the -2 diopter claims of 20/40 and I even heard one 20/30 claim!(he was correctable better than 20/10 is all thats known) Ive heard plenty of 20/100 claims with -3, all correctable better than 20/20 of course. Many were 20/15 I believe. I even heard one claim of 20/70 with -3, correctable to a full 20/10!

I will repeat(from a previous post here) what one optometrist said in a message board reguarding 20/something and diopters.

Optometrist: This is the UCVA our patients get with the following pescriptions

-1 20/30 to 20/40
-2 20/70 to 20/80
-3 20/100 to 20/200








Image
 
The amount of minification(or magnification) is 2% per diopter. My -5 glasses minify 10% which is enough to be noticable, everything I see is a little smaller than normal. Many things are too small for me to see without getting closer.

High myopes experience significent minification and can often result in costing them one or more lines as ive explained in my previous posts. Take an emmetrope and a -12.5 myope. The 20/25 line a -12.5 myope sees is minified 25%(2% per diopter) so therefore the 20/25 line for this -12.5 myope with glasses is minified so its equal to the size of the 20/20 line an emmetrope sees. Both have true 20/20 vision, the -12.5 myope has 20/25 BSCVA, however if he wears contacts, he would have 20/20 BCVA.

Image

Notice the 20/20 line and 20/25 line are the same size! With glasses the 20/25 line is the same size as the 20/20 line he sees with contacts!


Image

The eyechart an emmetrope sees or someone with a refractive error using contacts.

Image

Eyechart minified by 25%(to do the math, divide by 1.25 or multiply by .8) Notice that the 20/25 line is now the same size as the 20/20 line in the non-minified chart above!



Last edited by Myope5, 1/5/2006, 4:56 am
12/31/2005, 4:20 pm Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Hello everyone, post your dioptric pescription(how bad are your eyes), your UCVA(uncorrected) and BSCVA(corrected by glasses) Also if you know anyone's vision, post that too. I have done much research on the correlation of diopters and 20/xxx and have compiled several charts, formulae, tables and comments on the results obtained thus far. To test for this, do it in room light or dim light. Make sure the eyechart is well illuminated and your not squinting at all or recalling from memory or guessing. Blur preception is of course allowed.

I and most optometrists have found that -.25 diopters doesnt cost you a single line but makes the existing line blurry but still readable. Some say it costs half a line. Such as if you can see half of 20/15 with a -.25 lens, youll be a full 20/20 but wont be able to see better than that uncorrected. Another example is if your seeing all of 20/20, you may miss half of the 20/20 with -.25 diopters. Others have said it didnt affect their ability to read a line, just made it harder to do so.

Minus half diopter(-.5) is generally accepted as resulting in one full line loss. This means 20/15 becomes 20/20 and 20/20 becomes 20/25. If you can see half of 20/15 youll be seeing half of 20/20.

Minus one diopter(-1) generally gives you half visual accuracy. My friends who see 20/20 with glasses see 20/40 without their -1 glasses. Ditto for 20/15 with -1, 20/30 uncorrected. I was 20/50 corrected to 20/25 with a -1 lens years ago.

Higher dioptric values become harder to calculate and predict, especially when you get to -6 and up. Someone could be -4.5 another -5.25 and both see 20/400 UCVA. The -5.25 probably will see a much blurrier 20/400 than the -4.5 but generally, 20/400 represents a moderate of myopia around -5 diopters. One website said the range was -4 to -6 for 20/400 and your best corrected vision played a big factor. Someone whos 20/15 corrected needs more diopters to see the same blur as another with 20/30 corrected. For me, my left eye at -5 or so couldnt see 20/400 while my right eye at -4.5 or so just barely, barely saw 20/400. I know two people who passed V3 requirement which states you have to be 20/400 or better uncorrected and both were barely 20/400 with -5.5 pescriptions with 20/15 corrected. Those two guys said they dont know anyone else -5.5 or more who passed V3 which requires 20/400. They probably didnt have the great 20/15 corrected vision with glasses so for them, -5 was the limit(20/20 corrected) I am not correctable to 20/20 so my limit is even less.

Few eyecharts go beyond 20/400 so info is scarce past this. I have a solid grasp on dioptric values below -6(mild to moderate myopia), but for -6 and up which is high myopia I am less certain how this converts to diopters. I do know high myopes are worse than 20/400 but how bad exactly? Also theres much fewer high myopes than low and moderate myopes so much of my info is on low(er) myopes and their diopters to snellen accuracy.

One could stand closer but then accomodation needs to be taken into account. I can see the 20/200 E from 10 feet less blurry than the 20/400 E from 20 feet. At 5 feet I see the 20/70 line but im certainly worse than 20/280. I experienced .67 diopter accomodation from the 5 feet mark.

If any of you have charts and formulae, on what expotentional scale does this equal to? I know that going from -1 to -2 is only twice as bad(20/40 and 20/80), but going from -3 to -6 is definately more than twice as bad(20/150 and 20/500?), blurs much more than twice. Does this gap become even larger still at -6 to -12(20/500? and 20/????) where the number of times more blurry increases expotentionally?

Me and many others are curious about this and this topic has been posted before many years ago. Its also useful for some occupations such as pilot, soldier, law enforcement, etc where they have a requirement for both corrected(BCVA) and uncorrected(UCVA) vision and people ask all the time if their UCVA is good enough to make the cut.
1/10/2006, 6:13 am Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


My pre-op Rx and post-op results are:


           OS (left) OD (right)
Pre-op -9.00 sph +1.00 cyl -8.75 sph +1.75 cyl


2 weeks post-op -2.25 sph 0 cyl -1.75 sph 0 cyl


6 weeks post-op -3.25 sph 0 cyl -2.75 sph 0 cyl


The surgery only took about 10 minutes and was relatively painless. The
worst part was when they examine the cornea afterword with a VERY BRIGHT
light. You can't blink and the light is painfully bright, but it doesn't
last too long. The days and hours of anxious waiting before the surgery
is far worse than the actual procedure.


I had absolutely no post-op discomfort and haven't since, except for an
occasional dry burning sensation that goes away with eye drops. As you
can see from my results, I didn't get 20/20 vision on the first try. I
saw 20/70 the next day and have slowly regressed to about 20/100 or so.
Note to all you high myopes: 20/70 is damn good compared to whatever we
are at -9 or worse! Before, I couldn't read the big E on the eye chart.
Now, even with -3 d of nearsightness I can function without glasses,
which is something I could not do before, so it is a big improvement.

My comments: Hes giving the correlation between diopters and 20/xxx notice
hes seeing 20/70, presumbly with the better -1.75 eye. Also notice he regressed
to 20/100 then a little worse, perhaps 20/150 at -2.75
also notice at -9 theres no way he will see any snellen eyechart letters
not even the 20/800 E! -3 is a very, very big improvement when you used to be
a -9! Hes probably going to leave things well enough alone and not go for
a lasik enhancement due to his presbyopia and keeping his near vision intact.
Its not as much improvement for me where im a -4.5 and using a -1.5
trial lens gets me down to -3 but enough improvement to be noticable
but not quite enough to go "wow!" Give me a -3 trial lens and were talking
a significent improvement and I wish I were only -1.5 diopters! This
would be good enough to almost never need distance glasses, yet not need
reading glasses except for fine print.










Overall it was a good experience, but there was a complication with
epithelial depletion during the procedure causing extended healing time
and pain, and there seems to be 2.0 diopters of astigmatism caused by
the surgery in the right eye. I am a good 20/20 in the left eye, and a
bad, blurry 20/25 in the right eye, from my -7 to -8D pre-op
prescription.


My comments: -2 diopters of astigmastim is like -1 diopter spherical equivalent
It is somewhat supprising to still see any of 20/25 with this much astigmastim
or this much myopia unless your BCVA is better than 20/20







"The
vision was good, 20/25 unaided in that eye, correctable to 20/20 with
-.50"


My comments: aha! Diopters to 20/something revealed! This confirms that -.5 diopters
indeed does only cost one line of vision and is such a low refractive
error its not really myopia in the sense that its a problem, per see. I
consider low myopia -.75 to -2.75 and many agree with this.


When my post-op was -.25 and -.50 I was still 20/20.

My comments: I would not be supprised if a -.5 lens allowed him
to see at least some of the 20/15 line.



I just happened to be reading a book this morning, and came across
a table listing the relationship between refraction and acuity. (The book
is called The Laser Vision Breakthrough, and it said the table should only
be considered a rough guide. BTW - you'll learn alot about refractive eye
surgeries from the book, although my feeling is that it emphasizes the
positive aspects and sugar-coats the potential negatives)


The number to the left of the = sign is the spherical measurement.


No or minimal refractive error
    0.0 = 20/20(normal BCVA)
    -0.50 = 20/30(20/25)


Low myopia
    -1.0 = 20/50(20/40)
    -2.0 = 20/150(20/80)
    -3.0 = 20/250(20/150)
    -4.0 = 20/400(20/250)


Moderate myopia
    -5.0 = 20/500(20/400)
    -6.0 = 20/650(20/500)
    -7.0 = 20/800(close enough)


Extreme myopia
    -8.0 = 20/1000(20/800?)
    -9.0 = 20/1300(20/1000?)

Cant be really sure on the two above, but I am just going by my diopter chart formula but the formula may break down somewhere here.


My comments: I dont agree with some of them but for the higher pescriptions, the conversion doesnt seem too far off. Since few people are high myopes and since most eyecharts max out at 20/400 "E" its difficult and tricky to measure higher. I have extensive research on lower myopia. The pranthesis is my research results. They are somewhat too generous, especially in the lower myopia range.




I was close to your prescription. I had about 12 diopters (nearsightedness) in
each eye with an additional 3 diopters of astigmitism in each eye. My corrected
vision with contacts was no better that 20/25. I also needed reading glasses
(I'm 57).


My comments: Although not diopters to 20/20, this goes in agreement with my chart stating diopters to BCVA. 20/25 BCVA with contacts is not unusual for very high myopia. Extremely high myopes may have even worse BCVA






Your OD did a disservice by reccomending full time glasses wear. A low myope does NOT need glasses for close work, actually the opposite is true, he should NOT wear glasses for near, it will do nothing but cause eyestrain. Nearsighted means one can see great from near, so no glasses to be worn for near.

The ODs here already said not to worry about lazy eye.


You and your son can take measures to greatly slow the progression of myopia. Otis firmly believes in the plus lens theory to stop and even reverse the progression of myopia. An 8 year old probably doesnt want to bother with reading glasses when he sees fine from near. The next best thing to do is have him hold reading materials away from him and not 6 inches close like some people like to read at! Have him take frequent breaks looking off into the distance after doing prolonged near work. Keep him off the "evil" minus lens as long as possible and as long as he can see well without them. Once he can no longer see clearly without minus lens, wear glasses only for distance such as seeing the board in school or watching TV. Never wear glasses for near work.


"*If* there's anything you can do to slow the process, wean him from reading
and working very close ("nose in the book") and make sure he gets occasional
"far-vision" breaks while doing close work."


Good advice.


"After reading a bit in this group about Diopters vs. 20/xx I'm a bit
confused with the perscription I was given for my 8yr old ( see below )


R: -1.50 ( 20/100 vision uncorrected )
L: -0.75 ( 20/30 vision uncorrected )


To me it seems like a -0.75 is a very strong perscription for a child with
20/30 vision. I also had him try reading a snellen eye chart and came up
with more like ( R: 20/50 L: 20/30 )."


-.75 is right on the money to bring 20/30 back to 20/20. Weaker glasses wouldnt correct him to 20/20
There is no way he is 20/100 with only -1.5 diopters. Your testing him at 20/50 is more like it. Heck even I used to see 20/70 or 20/80 years back when I was -1.5 and I was only corrected to 20/25. Some optometrists dont know how to properly measure one's vision. I was proclaimed 20/20 before even though I guessed ONE letter right on the 20/20 line with correction.


"That's the problem trying to predict diopters from snellen acuity. Half the
time it's in the ballpark, the other half it's misleading."

actually, it should be in the ballpark all the time or something is wrong. Over 95% of people who post their pescription and UCVA fall in the ballpark. There is this one guy who was seeing only 20/60 with -.75 pescription, correctable to 20/20+ with glasses. He got lasik and is now -.5 after 6 months and sees 20/20. We went by the theory he was straining his eyes without glasses, resulting in tonic accomodation and hence increased blur. Glasses relaxed his eyes and tonic accomodation went away. I have done much research on the correlation of diopters to 20/xxx and for lower pescriptions, its much more predictable than for high pescriptions. Take a -1 for example, results typically in 20/40 UCVA. Take -4.5 or -5.5, both can still be 20/400 but the -5.5 would see a much blurrier 20/400.


"-0.75 isn't a "very strong perscription" no matter who has it."

Very weak pescription. Most people who get glasses for the first time are higher than -.75 and the vast majority of -1 and under rarely or never wear glasses.


"I was just trying to verify that 0.75 is not an
overcorrection for 20/30 vision"

If he corrects to 20/20, -.75 is right on the money.


"Wrong, ace, 20/30 is about right for -.75. If anything, I'd guess 20/30
is more like -1.00."


I am in agreement with this. I even have a thread on ***Diopters to 20/something conversion. The math and science behind this!***


Very interesting thread and I learned more about diopters to 20/xxx as well!!!!!!!! emoticon
1/17/2006, 3:49 am Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


The below is a repost in another thread but its fitting to be posted here too emoticon


Image


This is a similar example. The E is 20/400 then the W is probably 20/300(this one pictured doesnt have a 20/300 but some do) Next down is probably a 20/200 E. I believe theres 20/100, 20/70, 20/50, etc. Not sure if theres a 20/80, 20/150 but some projection charts have those too.


NOTE The exact example I saw when I got my eye exam is shown below! This is probably one of the more common ones. Notice the 20/400 E, the 20/300 W, the 20/200 E? Half the projector slides have this part. I have put the dioptric values. See my other thread to read all about it.
The following lines are as:

20/400(-5.25)
20/300(-4.50)
20/200(-3.50)
20/100(-2.25)
20/80(-2.00)
20/70(-1.75)
20/60(-1.50)
20/50(-1.25)
20/40(-1.00)
20/30(-.75)
20/25(-.50)
20/20(plano to -.25)
20/15(rare)
20/10(very rare)


There really should be a 20/150(or 20/160) line! There also should be a 20/13(or 20/12) line as well! I guess they dont consider it very important past 20/100 since your already seeing bad anyway and need correction at this point.

Image

Last edited by Myope5, 1/20/2006, 9:21 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


***My results with left eye***
plano to -.25...........20/30
-.50 diopters...........20/40
-.75 diopters...........20/50
-1.00 diopters..........20/60
-1.25 diopters..........20/70-80
-1.50 diopters..........20/100
-2.25 diopters..........20/150
-2.75 diopters..........20/200
-3.75 diopters..........20/300
-4.50 diopters..........20/400
-4.50 diopters, -.75a...20/500

*20/70 and 20/80 are nearly the same size making the difference insufficent



***My results with right eye***
plano to -.25...........20/40
-.50 diopters...........20/50
-.75 diopters...........20/60
-1.00 diopters..........20/70-80
-1.25 diopters..........20/100
-2.00 diopters..........20/150
-2.50 diopters..........20/200
-3.50 diopters..........20/300
-3.50 diopters, -1.5a...20/400

*20/70 and 20/80 are nearly the same size making the difference insufficent


Side by side comparsion(left)(rigt)
plano to -.25...........20/30 and 20/40
-.50 diopters...........20/40 and 20/50
-.75 diopters...........20/50 and 20/60
-1.00 diopters..........20/60 and 20/70
-1.25 diopters..........20/70 and 20/80

Side by side comparsion(left)(rigt)
The most important chart
20/40...........-.50 and -.25
20/50...........-.75 and -.50
20/60...........-1.00 and -.75
20/70...........-1.25 and -1.00*
20/80...........-1.25 and -1.00*
20/100..........-1.50 and -1.25
20/150..........-2.25 and -2.00
20/200..........-2.75 and -2.50
20/300..........-3.75 and -3.50
20/400..........-4.50 and -4.25

*20/70 or 20/80 is really almost the same. Sometimes I can see 20/70 at the same dioptric value as 20/80 depending how I interpret the blur and if I can get the eyes a little relaxed. There probably shouldnt even be a 20/70 line. On my dioptric chart in the first post, I put down -1.75 for 20/70 and -2 for 20/80. There is a difference but its slight and could go either way. A tired -1.75 may not bother focusing and see 20/80 while an alert -2 may strain to see 20/70.

Basically my right eye is about .25 diopters worse but not due to myopia, but irregular astigmastim which blurs as much as an additional .25 diopters in my left eye.



My right eye has a BCVA of one line worse so the same diopters gives me worse vision in the right eye. There is a big difference between BCVA and your UCVA with a given dioptric value. The reason for this is complex and irregular astigmastim as well as high order aberrations also factor in the blur. Uncorrected astigmastim of any kind costs lines. If I leave my -.75 astigmastim in the left eye uncorrected, it costs me one line. Irregular, complex astigmastim cant fully be corrected. You can approximate it in two ways, spherical equivalent and a "best fit" approximation using regular astigmatic lenses. See my previous posts for more explanations on BCVA, myopia and astigmastim.

I have about a diopter and a half of irregular astigmastim in the right eye. Spherical equivalent will get me to 20/40 with -4.5 diopters but letters are fuzzy and doubled. A -5 lens reduces more of the doubling but does nothing to improve the fuziness and also hurts my eye as its too strong. Using a -1.5 cylindar lens is much more accuate but since my astigmastim is assymetrical and irregular, it doesnt get corrected exactly, just approximated. Its like making an approximate sized round peg to fit in a square slot or vice versa.

I tried all combos and the best is -3.5 sphere and -1.5 cylindar. Optometrists generally like to go for spherical equivalent because its quick and easy. Mine always did that, especially in the right eye. The end result may be the same, but the quality of vision is NOT as good despite identical or one line less BCVA. I see 20/40 in the right eye with -4.5 sphere or -3.5 sphere+-1.5 cylindar but the quality of vision is better and theres none of the doubling that I see with the spherical equivalent. I would not reccomend spherical equivalent if more than -1 astigmastim when wearing contacts. I know this guy who sees 20/20 with glasses, 20/30 with contacts because his astigmastim may be like -2 diopters so they overcorrect him in one mederian by +1 diopters and undercorrect him in the other by -1. They cancel out, but results in blur. Hence his loss of two lines with contacts.

My snellen results are fairly accurate but some outside factors such as lighting and blur peception may slightly influence results. However the correlation follows a very close curve, generally within plus/minus a quarter diopter. I took the middle when reporting my results. My testing was done in a darkened kitchen with the hallway light illuminating the snellen chart and I look 20 feet down the hallway. This eliminates any pinhole effect due to constricted pupils. On the other end of the kitchen looking in the opposite hallway where the lights are brighter in addition to the bright lights in the dinning room, I can make out the same line with an additional ~half diopter more myopia. All diopter to 20/xx values are taken in room light which is fairly dim. Stay away from windows where the bright sun streams in or better yet do it at night like I did. Do make sure theres plenty of light illuminating the snellen chart but you dont want lots of light shining directly in your eyes!

Someone with a BCVA of 20/20 is of course going to see more lines with the same diopters as I will because I have astigmastim and high order aberrations contrubating to the blur. Some dont understand and think they should all see the same and that it doesnt matter. They couldnt be more wrong. Take my 20/40 BCVA in the right eye. I may have corrected myself to plano but I am still experiencing blur due to what glasses CANT correct. I can only correct all of my myopia and some of my astigmastims. Take another guy with 20/40 UCVA. If the reason he is 20/40 because of myopia, then glasses will improve his vision. If most of his 20/40 vision is due to astigmastim and high order aberrations, then only a small remainder is due to myopia. He may correct to 20/30 with a -.5 lens. The astigmastim and high order aberrations that dont get correct prevent him from seeing better than 20/30. There are a modest number of people that correct to 20/15, they have very few high order aberrations and better than normal optics. If a such person is seeing 20/40 UCVA, he may have -1.5 diopters of myopia. Instead of myopia, I have irregular astigmastims and high order aberrations.

We are just starting to develop technology to address those compound refractive issues. Defocus such as myopia and hyperopia is the easiest and was the first sort of correction to be invented some 700 years ago. Astigmastim is about 180 years old, having been invented in 1825! Check this article! Great read!!!!!!! We are now in the process of inventing wavefront glasses to further "fine tune" vision to beyond 20/20! High order aberrations is far more complex than your simple refractive error. Much is still being researched on this but imagine 20/10 being the new standard instead of 20/20! Two 20/40 guys may have different pescriptions, one could be -1.5 with few aberrations, the other -.5 with more aberrations!


Lastly, I posted this before but now that I have a trial lens kit for my testing purposes, I can much more accurately test my diopters to 20/xxx The results for each eye are with the astigmastim already compenstated for. This isolates myopia as the only varable. The values shown are with me undercorrecting myself in diopters and their corresponding visual accuracies I achieve. For example, a -.25 diopter undercorrection does not cost me a line but does make the existing BCVA line blurry but still visable. The bottom line of my results shows my visual accuracy without correction. I can barely see 20/400 UCVA in the less myopic right eye.

Why am I doing all this? Its fun and research and good record keeping to track my progress of vision improvement! Some people keep records of their weight loss, I keep records of my myopia loss emoticon

Last edited by Myope5, 1/27/2006, 9:44 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Bingo! I found a list of post-lasik patients, their pre-lasik diopters and UCVA and their post-lasik diopters and UCVA! Great for learning how diopters correlates to 20/xxx! I provided some links with my comments below the links!

http://la-sight.com/LS_commDetail.asp?index=142


Isnt this nice shes still 20/20 at -.5 and 20/25 at -.75? I wouldnt be supprised if she corrects slightly better than 20/20! I woulda thought she should definately see 20/200 UCVA, especially in her left eye!



http://la-sight.com/LS_commDetail.asp?index=141


Smart move correcting only one eye, the worse dormant one! His pre-lasik pescription does agree with the 20/400 UCVA, but might barely be 20/300 if he tried.



http://la-sight.com/LS_commDetail.asp?index=140


Sorry but her vision is NOT bad and NOT 20/200. He probably told her she was 20/200 otherwise she would never have gotten lasik. My friend is also -2 and was told hes 20/100 but actually tested out at 20/60! He corrects to 20/15 with glasses and this goes perfectly with my diopters to 20/xxx



http://la-sight.com/LS_commDetail.asp?index=138


20/30-(probably closer to 20/40) is not bad at all for being -1.25 diopters. Her -.25 eye is 20/20 and should be that way. Her results go in line with my diopter chart. I know -1.25 is generally 20/50 but she could correct to 20/20+ if plano. The evidence is shes still 20/20 at -.25!


http://la-sight.com/LS_commDetail.asp?index=137


Isnt this funny the same pescription as the lady above only gets 20/70? I bet they try to inflate results both ways, make your pre-lasik UCVA sound worse than it is then make your post-lasik vision sound better than it is! She should likley be 20/50 at -1.25 if she corrects to 20/20. By the way why didnt she laser only one eye or leave things alone? What a waste of lasik as she will be back in glasses, the reading type that is in a few short years!



http://la-sight.com/LS_commDetail.asp?index=136


Another diopter vs. 20/xx that doesnt match up. It would be in the ballpark for a 20/20 BCVA but since hes 20/15 he should be seeing better! Probably another example of inflating the results, make the pre-lasik UCVA as bad as possible


http://la-sight.com/LS_commDetail.asp?index=135


Concides fine with my diopter chart.



http://la-sight.com/LS_commDetail.asp?index=133


All her astigmastim must really blur things! She does have a spherical equivalent of -5.5 in the right eye, probably a little shy of 20/400. Wheres the 20/600 line? As for the -1 and 20/30, thats a darn good UCVA, probably slightly inflated by the surgeon to make it look good.


http://la-sight.com/LS_commDetail.asp?index=132


Very strange. Thats a rather good UCVA for the diopters and astigmastim. He got lasik and an enhancement for nothing, his UCVA was more than enough to function without glasses for near and distance. Lasik actually *increased* his dependancy in glasses, now he needs readers! I pity him! Yes 20/15+ is good but his pre-lasik 20/20- is more than functional to see great uncorrected.



http://la-sight.com/LS_commDetail.asp?index=130


-3.25 spherical equivalent, 20/15 after lasik. Should definately be 20/200 before lasik but I guess hes not good at interpretating astigmatic blur.



http://la-sight.com/LS_commDetail.asp?index=129


sees 20/25 with -.5 sphere and cylindar. Does go in line with my dioptric chart that -.5 diopters costs one line.



http://la-sight.com/LS_commDetail.asp?index=128


Goes in line for a 20/20 BCVA but should be seeing better than this.


http://la-sight.com/LS_commDetail.asp?index=126


His left eye is -.5 and plano in the right and has the same UCVA in both? I guess his BCVA in the left may be a little better than 20/20!



http://la-sight.com/LS_commDetail.asp?index=125


Ok this one makes perfect sense. -3.25 spherical equivalent for 20/200, corrected to 20/20



Read thru the rest. Isnt it funny almost everyone ends up with 20/20 and a third with 20/15? Many even have a tiny residual pescription such as -.25 or -.5 myopia and/or -.25 to -.75 astigmastim! Not enough to cost them a line. I dont know how they measure post-lasik vision but I bet theres lots of bias. Hey I was declared 20/20- when I went in for my lasik evaluation, the tech used the phororapter and "corrected" me to 20/20- If its like that for many people, then I know the truth! Most/many of them are a line(or two!) worse than they actually are! I even heard in a few centers, they cheat somewhat by moving the projector closer so every letter is like 20% larger. Suddenly your 20/20 is really only 20/24! Theres many other factors, see my thread here!


http://com5.runboard.com/bwelcometothevisionandeyeforums.flasereyesurgery.t42


Anyway to conclude diopters to 20/xxx half the results are right on the money, the other 25% are in the ballpark and the last 25% are way off! Perhaps some people are unwilling to make any effort to interpret the blur and just say "I cant see, I cant see!!!!!!!" or maybe they "miss" on purpose to gain symphathy. Or perhaps they are straining so hard, things instantly become alot blurrier. I have researched my own results and I can tell you right now that -2 is MUCH better than 20/200. I only correct to 20/30 in the better left eye and with a -2 undercorrection, 20/200 is not even an effort to see. Its a little blurry but no straining or interpretation needed, its clear enough to readily be seen. Even 20/150 is not much of a problem! Those who correct very nicely, such as a true 20/15 will see 20/60 or 20/50 to 20/70 with a -2 pescription! See my diopter chart in the previous posts, youll see!

The 50% of the results that are on the money concide with my diopter chart. Those people are seeing 20/200 in the -3 range and 20/400 in the mid -4 to -5 range! They see better than 20/200 with mild myopia of less than -3! One guy was 20/100 at -2.75, corrects to 20/15, another 20/80 at -2.25, a third still was 20/70 at -2! I stand by my diopter chart research, although I admit I am a bit uncertain about the correlation if you are a high myope(-6 or more) because I havent done extensive research on this. Read my earlier posts for further comments reguarding this.


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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Image


I found this image here! Note that if plano results in 20/15 for this particular person, he would be seeing 20/30 at -1, 20/60 at -2, and a little shy of 20/100 at -3. The simulated blur explains it all. My friend sees 20/60 at -2, 20/15 BCVA. See my diopter chart in the previous posts for details.


So how good do I consider the following visual accuracies?

20/2=eagle vision. I highly doubt any human will see this good naturally. It may be possible with bionic eyes, genetic engineering to produce a mutant or perhaps remove a part of your retina and replace it with one of much higher density rods/cones.

20/3=Probably the very, very best a human will ever see naturally. May be the world record. Youd need to be a freak of nature with 1000% perfect eyes.

20/4=half eagle vision. The smallest line my printed snellen chart goes down. Its believed this is the ultimate limit of vision experts believe a human can ever have, hence thats the smallest line the snellen chart I found on the web to print has. You could make and print your own as small as capable of your printer.

20/5=hawk vision. Probably one in a billion humans see this good. Some experts dont even think a human can be capable of vision this good.

20/6=near hawk vision. The limit to human vision agreed by most experts. Some will argue humans may be capable of even better!

20/8=godly human vision and near the limits of human vision. Probably one in 5000 humans see this good

20/10=exceptionally good vision. I read that one in 1000 humans see this good, but I take the optometrist word that he says less than 2% see this good, its about 1% accroding to him. Thats 1 in 100!

20/13=very very good vision. Probably 1 in 15 humans see this good.

20/15=very good vision. Id estimate 1 in 4 humans see this good.

20/20=standard for normal vision. about 2/3 of humans see this good with or without correction. The rest see worse and not many see better.
20/25=still normal vision, very near "perfect"
20/30=very good vision
20/40=legal to drive anywhere
20/50=good vision, very rarely need glasses
20/70=fair vision, occasional need for glasses
20/100=minimum one can go without glasses and still see well enough
20/150=inadequate vision
20/200=legally blind if BCVA
20/300=bad vision
20/400=very bad vision
20/worse=functionally blind. Highly dependant on glasses


Last edited by Myope5, 2/4/2006, 2:08 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


While not diopters to 20/xxx, its about diopters to BCVA. I have mentioned this in part in my previous posts. The excerpt below shows how bad very high myopia is in both terms of 20/xxx and BCVA!




"Luckily, I never did develop major retinal changes that we see in high myopes."

This is why very high myopes(-10 and up) sometimes(fairly commonly) cant correct to 20/20 with contacts and even worse with spectacles(due to minification) One optometrist who posts on google groups said he sees patients around -15 diopters(myopia in the teens) with only 20/40 to 20/50 BSCVA. Looking at my notes, this guy whos -18 diopters can only correct to 20/60 with glasses. I know several more around -10 with 20/30 in glasses. One guy was -14 and 20/30 BSCVA, 20/25 with contacts which dont minify. ***additional comments*** in my previous posts, I mentioned diopters to BCVA in terms of averages. The correlation isnt as close as is the correlation between diopters and 20/something. -8 for 20/25 -12 for 20/30, -18 for 20/40, -27 for 20/60 are four examples for BSCVA.



Hi, I'm 17. My perscription is -6.00 in 1 eye -6.50 in another, and -1.25
antagotism(sp) in 1 eye and 1.00 in the other. I believe I was 20/800


My comments: Hes correct about the 20/800 in the worse eye, were talking
a spherical equivalent of -7 or just over that. The better eye would
be -6.5 spherical equivalent and probably good enough to see a blurry 20/600



Thanks for the reply.
With glasses my vision is:-
PMT< -18.00/-2.00 DC X 170 -6/18 - NI
-17.00 DS - 6/18 - NI

Doctos have advised me to go for a LIO.I do not know what is it.Please tell me about it.Should I go for it or not.Is there any risks involved in it.And what is advisable.



My comments: Due to his pathalogic myopia, hes experiencing retina problems
including small holes and possible detachments. Spectacle minification
also plays a role in addition to his pathalogic myopia which results in 20/60 BSCVA



The nurse had my vision without my glasses on at 20/20 left eye, 20/15 minus three right eye,
and 20/15 minus 1 with both eyes. My prescription is -.50(right) and -.75(left)


My comments: I cant believe your optometrist pescribed you glasses and made you wear them even though you are 20/20 without them! Legal driving requirement is 20/40, you are well above that! Me thinks he just wanted to make a sale on glasses! I know of many cases like that, one guy was +.5 diopters and could see perfect from all distances(he was young too) and the optometrist still said he needs glasses. The parents took him to another optometrist who said dont even bother with glasses. I think you need another opinion. Wearing those glasses will just make your eyes worse than you wont be 20/20 without glasses anymore emoticon Man I am upset now, I cant believe some optometrists! emoticon emoticon emoticon


******************
Side by side comparsion(left)(rigt)
*The most important chart*
20/40...........-.50 and -.25
20/50...........-.75 and -.50
20/60...........-1.00 and -.75
20/70...........-1.25 and -1.00*
20/80...........-1.25 and -1.00*
20/100..........-1.50 and -1.25
20/150..........-2.25 and -2.00
20/200..........-2.75 and -2.50
20/300..........-3.75 and -3.50
20/400..........-4.50 and -4.25

*20/70 or 20/80 is really almost the same. Sometimes I can see 20/70 at the same dioptric value as 20/80 depending how I interpret the blur and if I can get the eyes a little relaxed.

Let me repeat this chart. As you can see, I am already 20/400 UCVA in the less myopic right eye and just shy of 20/400 in the left. Just .75 diopter additional improvement will get me 20/300 in the right eye. 1 to 1.25 diopter improvement will make the 20/300 considerabily easier to see. At the rate of my improvement, I should achieve another diopter improvement by the start of year 2007 and be 20/300 in at least one eye and possibily both! emoticon emoticon emoticon
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