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


Ok, so my prescription is -1.25L and -0.5R. I can still see 20/20 but I need the prescription to see my original 20/10. Guess it makes sense.

But I don't feel like bothering with numbers. In the end, all that matters is that you see what you need to see and you don't feel uncomfortable emoticon
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Yea you dont care what diopters you have as long as they improve and you become 20/20 or better without glasses at all times emoticon
Diopters are a measurement of how much defocus your eyes have. A phororaptor uses lenses and you say which is better, one or two to arrive at what diopters you have for BCVA. There are many factors and my diopter chart is more of an estimate than a hard tell at exactly what diopters you have. There are other factors in the eye that contribute to blurring besides diopters. I use the near test because its a relation to the diopters you have. Someone whos -4 is going to see best at 1/4 meter, it does not have to be 100% clear due to other factors such as astigmastim. Different people with -4 diopters may see 1/4 meter clearer than others but one thing in common is everyone will see 1/4 meter clearer than closer or further.


What is a Diopter?
A diopter is a unit of measurement of the refractive error. It may be a negative number (myopia, nearsightedness), or a positive number (hyperopia, farsightedness). A -1.00 diopter myope is able to see objects at 1 meter clearly. A -2.00 diopter myope is able to see objects at a ½ meter clearly. The greater the myopia, the strength of the lens in diopters needed to correct the refractive error, and the closer an object must be to be viewed clearly.
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


There is a huge difference between near and distance vision. You see differently at all distances. So you "need" a different pair of glasses for seeing at 10 feet, at 11 feet, etc. Of course a few feet wouldn't make such a difference, but 20 feet would. That's why vision is measured at 20 feet.
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


yup! actually they measure near vision of those who are farsighted and far vision for the nearsighted emoticon
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


http://www.mattmcmahon.com/eyeknowwhy/threat.htm


See link above, scroll down near bottom of page. This goes closely in agreement with my diopter chart.

-.75 equals 20/30
-1 equals 20/40
-1.5 equals 20/60


They got undercorrected after lasik. The lower myopes were seeing 20/20 clearly with glasses while the higher ones 20/25(due to minification)




Last edited by Myope5, 9/8/2005, 11:04 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


 My vision was -.50, -1.25, 95 in my right
and -1.00, -1.25, 85 in my left, mild myopic with astigmatism.
Most of the haze is gone from both and my vision in my right
eye is sharp 20/25, however I'm noticing a bit of ghosting which
is really annoying and no ghosting in my left eye but it's not as
sharp as my right, 20/40. Will my left eye get sharper? To be
honest, I'd rather have the 20/40 with no ghosting.


yet another example! Since he has astigmastim whereas my diopter chart numbers are just for myopia, hes correctable to at least 20/15. Someone correctable to 20/20 at -.5 and -1 would be 20/25 and 20/40. He has this much myopia *with* -1.25 astigmastim so unless hes correctable to better than 20/20 he will not be seeing 20/25 and 20/40
9/15/2005, 1:48 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!


Youve seen diopter charts and some explanations, well heres more!


-.5 diopters is so little its not considered myopia in the real sense. It can be measured as such but still within emmetropia norm. No action needs to be done in this case. If your BCVA is 20/20, youll probably be 20/25 then. Whatever else your BCVA is, expect a one line loss. Most people dont even notice this unless they flip a -.5 lense rapidly. This is little more than threshold where they can see any difference at all. My example is 20/30 BCVA, 20/40 with -.5 undercorrection

-1 diopters is a small amount of myopia which results in a small blur. It results in the loss of 3 lines or about half vision from your BCVA. If your correctable to 20/20 you should still be legal to drive at 20/40. Many people with just a diopter dont wear glasses. Others are very picky with even a small amount of blur and wear glasses sometimes. If your worse than 20/20 BCVA you still wont need glasses except for driving. My example is 20/30 BCVA, 20/60 with -1 undercorrection

-1.5 diopters will result in the loss of 5 lines. This may sound alot but its really not nearly as bad as one may think. Youd have about a third BCVA but one shouldnt feel limited without their glasses unless they are trying to read the board or projector from back of class or drive at night. 20/20 becomes 20/60. My example is 20/30 BCVA, 20/90 with -1.5 undercorrection

-2 diopters will result in about fourth to fifth vision. If your BCVA is not very good then your resulting loss will be less. a 20/20 will be reduced to 20/80 to 20/100, my 20/30 becomes 20/120. a 20/70 may become 20/200 to 20/250.

-3 diopters results in eigth to tenth vision. This begins the realm of moderate myopia. One with three diopters would be dependant on glasses more time or even full time. Few people with this myopia see 20/100 unless your BCVA is like 20/10 maybe 20/12. 20/150 to 20/200 is a common range. If your BCVA is less like 20/30 to 20/50 you may be seeing 20/300 then.



If 20/15 BCVA


-.5 20/20(-1 line)
-1 20/30(-3 line 1/2 vision)
-1.5 20/50(-5 line 1/3 vision)
-2 20/70(1/5 vision)
-3 20/150(1/10 vision)


If 20/20 BCVA


-.5 20/25(-1 line)
-1 20/40(-3 line 1/2 vision)
-1.5 20/60(-5 line 1/3 vision)
-2 20/100(1/5 vision)
-3 20/200(1/10 vision)


If 20/25 BCVA


-.5 20/30(-1 line)
-1 20/50(-3 line 1/2 vision)
-1.5 20/70(-5 line 1/3 vision)
-2 20/120(1/5 vision)
-3 20/250(1/10 vision)


If 20/30 BCVA


-.5 20/40(-1 line)
-1 20/60(-3 line 1/2 vision)
-1.5 20/100(-5 line 1/3 vision)
-2 20/150(1/5 vision)
-3 20/300(1/10 vision)


This summarizes it up. A bit of rounding may be used as theres no 20/75 nor 20/90 line unless you make your own custom snellen emoticon



Last edited by Myope5, 9/19/2005, 3:28 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Comments about the first diopter chart. I read it again and noticed a contridiction! Look at the -18 for example. One with such extremely severe myopia on average has a 20/40 BCVA with glasses. Even compenstating for minification, the myope would see 20/29.4 meaning the 20/40 letters to that myope would be as small as 20/29.4 to an emetrope or one with contacts, intacts, IOLs, lasik, etc which doesnt minify. Therefore this unfortunate myope would see *worse* than 20/3200.

The 20/whatever values are for 20/20 BCVA compenstating for minification. It becomes rare for this to be the case in extremely severe myopia. Therefore the actual values are somewhat worse, but for simplicity, all values listed apply for 20/20 BCVA. Just adjust accroding to actual BCVA. BSCVA is a useful term when signficent minification is involved. This generally starts at more than 10% minification. Less than that and any BCVA is more or less the same. With high pescriptions, BSCVA is usually less than BCVA which can be achieved if the myope wears contacts as corrective lenses.

Lets do the math. Glasses have a vertex distance of 20 milimeters. Contacts sit on the eyeball so their vertex distance is the thickness of the contacts. Lets take a worst case scinerio: 2 milimeter thick RGP contacts with -30d correction which is as high as they go. Since the vertex distance is 10%, the minification is a tenth as much. Therefore theres only 6% minification. This is like standing 21.2 feet instead of 20 feet from an eyechart. Soft contacts max out at about half the pescription so therefore half the thickness and minification in worst case.



diopter/snellen/inch(feet)/centimeter/comments



-0.7 20/30 .51/1,32 near perfect vision. The lucky minimal myope would and should not find correction neccessary except in rare, extreme situations such as sharp shooting, sightseeing and flying air vechiles.




-1.05 20/40 .68/1.76 driving legal, forget glasses. All but the most strict myope would be content going around uncorrected for normal daily activities. There is very little blur involved.



-1.58 20/60 1.02/2.64 might need driving glasses. This depends on the state and country you reside in. Dependancy on glasses is very low with this mild refractive error. This myope may find glasses not neccessary in familar surroundings such as in his own home.



-2.37 20/100 1.7/4.4 need glasses part time. This refractive error is bad enough to have some dependancy on glasses. However glasses should not be worn for close range, including computer usage.


 
-3.55 20/200 3.4/8.8 need glasses more time.
This is a moderate amount of myopia and the myope may find the blur unacceptable for many activities. However the near point would be about a foot making reading, eating and other close works possible without correction. Minification is only 7% making the 20/20 line 20/18.7 so its fairly insignficent.


 
-5.33 20/400 6.8/17.6 need glasses full time
This poor myope, although still in the (higher)moderate range is legally blind without correction. Reading is possible without correction but the article would need to be moved quite close to your face. A reduced pescription or bifocal glasses may be used for reading and using the computer.
Minification is 10.7% making the 20/20 line 20/18.1 resulting in some trouble reading the 20/20 line. Many with this pescription are 20/25 BSCVA

 
-8 20/800 13.6/35.2 can count fingers from 5 feet. This poor person has severe myopia and is reduced to CF count finger vision. Minification is 16% making the 20/20 line 20/17.2 making most with this pescription 20/25 BSCVA. Its quite unusual to have 20/20 BSCVA with this amount of myopia and minification. Some dont even have 20/20 BCVA either!



-12 20/1600 27.2/70.4 can barely see and count own fingers. This myope would see blurry fingers when holding hand away from face. BSCVA of 20/20 is rare due to 24% minification rendering it 20/16.1 BCVA of 20/20 is unusual as well due to very severe myopia.


-18 20/3200 54.4(4.5)/140.8 20/40 with glasses. 20/20 with glasses becomes 20/14.7 due to 36% minification. Even the 20/25 line becomes 20/18.4! Your typical extremely severe myope sees 20/40 with glasses which becomes 20/29.4 without minification. 20/30 is then possible with -14.5 contacts, however its almost impossible to find soft contacts that go this high. Many either wear RGP contacts or -12 contacts and thin -3 glasses. The latter has the advantage in that the myope can remove glasses and see clear from near which is useful for reading and eating.


 
-27 20/6400 108.8 (9.1)/281.6 20/70 with glasses. If this myope chooses RGP contacts, his BCVA will improve to 20/45.5 due to avoiding the 54% minification of glasses. I know one -24 guy whos 20/40 BCVA(which is fairly unusual), thats 20/27 without minification. He does achieve 20/25 with RGP! Considering a UCVA of about 20/6000, thats a 240x improvement in BCVA! Talk about a BIG difference correction makes!



-40.5 20/12800 217.6(18.1)/563.2 20/150 with glasses. The strongest RGP, -30 would undercorrect the person by -3 diopters in glasses. Not that any complaints should be forthcomming from such a large partial correction of myopia without significent minification. Even if full correction was achieved with very thick RGP, were talking a BCVA of 20/82.9!


-60.75 20/25600 435.2(36.3)/1126.4 legally blind with glasses. Its extremely rare for someone to become this myopic! Most become completely blind from retina detachments and other maladies, usually well before reaching this pescription! BSCVA is worse than 20/200 and in many cases, 20/400 or worse! The minification is so great being 121.5% his world is literally less than half size! No contacts come near this pescription.



http://www.iwant2020.com/ewc-testimonials.htm#da

Heres some diopter results vs. 20/something. I disagree with some of them, they are either too low or too high. The ones that are too high are as follow below:

RX: -5.00-50x4
Visual Acuity: 20/250

Original RX: -8.25-.50x104
Visual Acuity: 20/400


The -5 guy would be no better than 20/400!
The -8.25 would be 20/1000 or so! Both probably squinted or guessed!

Those following are too low:

Original RX: -1.50-1.25x92
Visual Acuity: 20/200

Original RX: -3.00-0.75x20
Visual Acuity: 20/400

Original RX: -2.75-.50x161
Visual Acuity: 20/400

-1.5 diopters with low astig should be 20/100
The -3 guy should be 20/200
Ditto to the -2.75 guy.

Those following sound spot on:


Original RX: -4.25-1.00x170
Visual Acuity: 20/400
My comments: Might be a blurry 20/300 though


-3.75-0.75x180 L
20/200 Left
My comments: Was probably 20/15 BCVA pre-lasik

Original RX: -1.75 R
-1.50-0.50x15 L
Visual Acuity: 20/70
My comments: Thats spot on accroding to my diopter chart.

-0.75-2.00x81 L
Visual Acuity: 20/100 Left
My comments: Very low myopia, but moderate astigmastim. Would be about as blurry as -1.75 diopters myopia equivalent.


Original RX: -3.50-.50x9
Visual Acuity: 20/200
My comments: Blurry 20/200 UCVA. Ended up 20/20 UCVA post lasik. In agreement with my diopter chart.


Original RX: -5.50-0.25x151
Visual Acuity: 20/500
My comments: Not quite clear enough to see 20/400 unless 20/15 BCVA. Got 20/20 UCVA post lasik.









Last edited by Myope5, 9/28/2005, 5:46 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I also disagree with "hand motions" We are talking 20/2000 at HM 20' First comes CF for count fingers and none of those guys who got lasik were worse than CF vision, well maybe except for that -12 lady with ambylombia.


Another point that some people have disagreed with me is reguarding BCVA. Not everyone has 20/20 BCVA, especially if their UCVA eyesight is poor. Mine is 20/30 BSCVA, although I believe I could achieve 20/25 with contacts, especially RGP which provide the clearest vision. However I never wore RGP and have only tried samples of soft contacts but I stick to glasses for correction. High order aberrations are the most common curlpit which cant be corrected by anything but wavefront lasik. RGP may reduce HOA's though, hence why they provide especially crisp BCVA vision. I dont have any eye diseases and never had a lazy eye.

"In a study involving 10 eyes of seven myopic patients, with a mean age of 34.8 years and a mean refractive error of -12.75 D, the postoperative mean spherical equivalent (SE) was -1.36 D at six months follow-up. In addition, the mean BCVA improved from 20/30 to 20/25 and there was no increase in mean cylinder."


Hence I was right. Another article talked about putting IOLs in as high as -28 with BSCVA of 20/100! BCVA varies on many factors such as high order aberrations, minification, your pescription, etc. Very high amounts of myopia are often the result of pathalogical myopia which stretches the retina and causes macular degradation among other maladies. This accounts for about 2% of myopes and much of the 2% with very severe myopia of -10 and up.


Summary of my research:
diopter/UCVA/(percent minify)BSCVA and BCVA

-3.55 20/200(7%)20/20 and 20/20
-5.33 20/400(10.7%)20/25 and 20/20
-8 20/800(16%)20/25 and 20/20
-12 20/1600(24%)20/30 and 20/25
-18 20/3200(36%)20/40 and 20/30
-27 20/6400(54%)20/60 and 20/40
-40.5 20/12800(81%)20/100 and 20/55
-60.75 20/25600(121.5%)20/200 and N/A
-91.13 20/51200(182.3%)20/500 and N/A
-136.69 20/102400(273.4%)20/1600 and N/A

I have rounded the above figures to the nearest snellen number. Those above figures are also for the average, some may have a 20/15 BCVA or even BSCVA while others 20/40 even with mild myopia. Expect average BSCVA to start dropping at -5 and BCVA to drop at -10. Therefore if you are less than -5 average BSCVA is 20/20. If you are less than -10, average BCVA is 20/20. If less, then greater amount of high order abberations is usually to blame. Those with -10 or more have an average BCVA worse than 20/20 and BSCVA even worse due to minification.

less than -5 20/20 with glasses or contacts

-5 to -9.75 20/25 with glasses, 20/20 with contacts.

-10 or more is very severe myopia(often pathalogical) and on average worse than 20/20 even with contacts.


An easier to understand table:

Glasses:

less than -5 for 20/20
-5 to -7.75 for 20/22*
-8 to -11 for 20/25
-11.25 to -15 for 20/30
-15.25 to -20 for 20/40
-20.25 to -25 for 20/50
-25.25 to -29 for 20/60
-29.25 to -33 for 20/70
-33.25 to -36 for 20/80
-36.25 and up for 20/100 and worse


*although theres no such line, results
would typically fall there.


Contacts:

less than -10 for 20/20
-10 to -15 for 20/25
-15.25 to -20 for 20/30
-20.25 to -25 for 20/35*
-25.25 to -29 for 20/40
-29.25 to -33 for 20/45*
-33.25 to -36 for 20/50
-36.25 and up for 20/55* and worse

*although theres no such line, results
would typically fall there.

Its much harder to estimate what your BCVA will be with the given diopters. Much easier to convert diopters to 20/xxx and this is constant, predictable and reliable to a high degree. However with BCVA theres too many factors to be predictable. I can only provide averages such as being -10 or worse will typically average less than 20/20 even with contacts.

Glasses BSCVA comments:

Minification plays a role. Its a gradual process that slowly drops the average. Simply put, the higher your minus lense, the harder and less likley to see 20/20. Theres many borderline cases where the subject can still see 20/20 but not all of it. If he cant see enough of the 20/20, hes considered 20/25 although it may be proper to destinate 20/25+ if he can see a number of letters on the 20/20. At exactly -12.5 diopters, the 20/25 line will be minified exactly to the same size as the 20/20 line. However someone with this much myopia will on average be 20/30. At exactly -25 diopters, the 20/30 line will be minified exactly to the same size as the 20/20 line. However someone with this much myopia will on average be 20/50.


contacts BCVA comments:

Without any measurable amount of minification, there is no artificial limit unlike glasses. This is why contacts are so popular for very high myopes. They provide a natural, true-to-life vision. Their glasses minify and disort a fair amount plus can be thick, heavy and unsightly. Very high myopes are more willing to put up with contact discomfort because of the significent difference in vision achieved. Ideally, you want 20/20 vision reguardless of your pescription. However on average, this isnt the case. If your less than -10, 20/20 is indeed the average. If its in the teens, 20/25 to 20/30 is more common, although 20/20 is certainly possible, but less common the higher above -10. More than -20 and still being corrected to 20/20 is definately going to be impressive not to mention uncommon and the higher above 20/20 the rarer. Even 20/25 and 20/30 are considered above average if you have such high myopia. I also have seen very, very few such high myopes, only a tiny fraction of one percent are higher than -12, -15 and especially -20! This is often pathalogical and most certainly not normal! All sorts of problems may arise from this, including decreasing BCVA.




Since my BCVA is 20/25 compenstating for glasses minification, I have more high order aberrations than average as do many people.
Im about a -5 in glasses and 20/27.5(about 6/8 metric) but theres no such line on standard eyecharts. Theres a 10% minification with glasses so this makes me 20/25 compenstating for minification. 20/25 with contacts or 20/27.5 with glasses equals same size snellen letters. I did used to be 20/25 with glasses back when I was -1 which only minified 2%
The lucky ones with few HOA's experience 20/15 or even better, compenstating for minification of course if a glasses wearer. Someone -8 that sees 20/15 with glasses would be 20/13 with contacts. The 20/15 line with glasses would be minified to 20/13 therefore 20/13 with contacts or 20/15 with glasses are equally impressive and equally tiny.

Im actually worse in the right eye but my dormant left eye is the better BCVA one.

Left: 20/27.5(6/8) glasses, 20/25(6/7.5) if contacts or compenstate for minification. Since theres nothing between on snellen chart, 20/30 is the next line.

Right: 20/33(6/10) glasses, 20/30(6/9)if contacts or compenstate for minification.
Since theres nothing between on snellen chart, 20/40 is the next line.


update!

It is not uncommon for high myopes to have slightly subnormal BCVA. This
can be due to retinal malformation and is often very stable; ie it does not
get worse with time.


I was correct and agree with this optometrist's fact! In addition to spectacle minification, high myopes often have problems with their retina among other things. I read on one website that did a clinical trial on IOLs and they said the average patient pescription was -12.75 and 20/30 BSCVA and the range was -6 to -24 with BSCVA from 20/20 to 20/100!


I know very, very few super myopes but there was one in a different forum who was -24 and 20/40 with glasses, 20/25 with RGP because of glasses minification plus RGP is superior anyway! That admittaly is a decent BCVA for such a high myope too! I read around that myopes start having trouble seeing 20/40 with glasses once they get to -20 or the low -20 range. A -18 on average will resolve 20/40 with glasses but it becomes problamatic past -20 to -22.

On the flip side, ive seen some unusual and barely believable cases. My female friend says she used to be 20/15 with -10.5 glasses till she was around 40 then it worsened to 20/20 but still darn good. I called her bluff but she swears by it. I said thats highly unusual and she says nah not really, I know a couple friends like that too and several others at 20/20. She did mention that she knows some not correctable to 20/20 and one only 20/50 but he had an eye disorder as a child. She also claims minification doesnt really matter, the difference isnt enough to "cost" you any lines. Yea, yea thats easy for her to say because shes 20/20 and was 20/15 for a while. Just because she had an exceptional BCVA doesnt make it the norm and doesnt mean minification doesnt matter, it does!

I know another young lady whos a -10 now and shes losing her ability to see 20/20 with glasses due to minification but still sees 20/20 fine with contacts. Several people have told me you should see 20/20 with glasses up to -8 or so and said my 20/30 at -5 isnt normal. I told them im really only one line from normal because my glasses make the 20/25 a little too small to accuratly see, but if forced to guess I can see 1/3 to 1/2 of it depending how lucky I get. I also added that I should see most or all of 20/25 with contacts. Having extra high order aberrations can easily account for this.





Last edited by Myope5, 12/23/2005, 12:06 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


My results with both eyes tested together(OU)(If my BCVA was 20/20):


plano 20/30+(20/20)
-.25 20/30(20/20 but blurry)
-.5 20/40(20/25)
-.75 20/50(20/30)
-1 20/60(20/40)
-1.25 20/70(20/50)
-1.5 20/80(20/60)
-1.75 20/100(20/70)
-2 20/120(20/80)
-2.5 20/150(20/120)
-3 20/200(20/150)
-3.5 20/250(20/200)
-4 20/300(20/250)
-4.5 20/400(20/300)
-5 20/500(20/400)


a repost from the above, but I wanted to go into details and also talk about intacs. As you noticed in diopters vs. 20/something, going from -5 to -2 would give me more than 4 times better vision! Even if I end up -2.5 thats still more than 3x! My dependancy on glasses would be reduced by 75% as long as I can see well enough to use the computer without em!

I can barely make out the 20/400 E on a good day and id consider myself 20/500 on average. My mom is -7.25 with -.75 astigmastim(in her better eye(her worse is -8.25) and has a 20/30 BCVA like me. She would see as bad as a -8.25 without asig correctable to 20/20(with contacts)20/25(with glasses) This would translate to about 20/900!

my last check measured -5.5 with -.5 astig(left) and -5(right) but I believe its less than that now. Both eyes see very nearly equally bad and my near point test reveals -5(left) -4.75(right) which makes me a bit shy of 20/400! Trying to simulate my mom's pescription with +2.5 reading glasses yields a blurry 20/800! If I stand another couple feet further, I cant see it.

Last edited by Myope5, 11/4/2005, 1:45 am
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