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


For convinence, I have placed the three most important charts in the first post. Those figures are for pure myopia with zero astigmastim. Update: I have edited my post to change my diopter chart a bit and add higher diopters and make some corrections. All of them take into account 20/20 best correction, compenstating for glasses minification of course. Contacts have viturally no minification. Take a -12.5 that achieves 20/25 with glasses(which is above average BCVA for the matter)his 20/25 letters with glasses would be minified exactly the same size as if he wore contacts which would then give him 20/20. 20/25 with glasses, 20/20 with contacts are equally good, the letters being equally tiny. His true BCVA is 20/20. If 20/30 with glasses, then his true BCVA would be 20/24 if we compenstate for minification. His UCVA would be then worse than what my diopter charts below indicates.


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



-0.7 20/30 .51/1.32 near perfect vision
-1.05 20/40 .68/1.76 driving legal, forget glasses
-1.58 20/60 1.02/2.64 might need driving glasses
-2.37 20/100 1.7/4.4 need glasses part time
-3.55 20/200 3.4/8.8 need glasses more time
-5.33 20/400 6.8/17.6 need glasses full time
-8 20/800 13.6/35.2 can count fingers from 5 feet
-12 20/1600 27.2/70.4 can barely see and count own fingers
-18 20/3200 54.4(4.5)/140.8 20/40 with glasses
-27 20/6400 108.8 (9.1)/281.6 20/60 with glasses
-40.5 20/12800 217.6(18.1)/563.2 20/100 with glasses
-60.75 20/25600 435.2(36.3)/1126.4 20/200 with glasses
-91.13 20/51200 870.4(72.5)/2252.8 20/500 with glasses
-136.69 20/102400 1740.8 (145)/4505.6 20/1600 with glasses



A. -0.7 ...... 20/30
B. -0.88 .... 20/35
A. -1.05 .... 20/40
B. -1.32 .... 20/50
A. -1.58 .... 20/60
B. -1.98 .... 20/80
A. -2.37 .... 20/100
B. -2.96 .... 20/150
A. -3.55 .... 20/200
B. -4.44 .... 20/300
A. -5.33 .... 20/400
B. -6.67 .... 20/600
A. -8 ......... 20/800
B. -10 ....... 20/1200
A. -12 ....... 20/1600
B. -15 ....... 20/2400
A. -18 ....... 20/3200
B. -22.5 .... 20/4800
A. -27 ....... 20/6400
B. -33.75 ... 20/9600
A. -40.5 ..... 20/12800
B. -50.63 ... 20/19200
A. -60.75 ... 20/25600
B. -75.94 ... 20/38400
A. -91.13 ... 20/51200
B. -113.91 . 20/76800
A. -136.69 . 20/102400


This verson below has been rounded to .25


A. -0.75 .... 20/30
B. -1.00 .... 20/40
A. -1.25 .... 20/50
B. -1.50 .... 20/60
A. -1.75 .... 20/70
B. -2.00 .... 20/80
A. -2.25 .... 20/100
B. -2.50 .... 20/120
A. -3.00 .... 20/150
B. -3.50 .... 20/200
A. -4.00 .... 20/250
B. -4.50 .... 20/300
A. -5.25 .... 20/400
B. -6.00 .... 20/500
A. -6.75 .... 20/600
B. -7.25 .... 20/700
A. -8.00 .... 20/800
B. -9.00 .... 20/1000
A. -10.00 .. 20/1200
B. -11.00 .. 20/1400
A. -12.00 .. 20/1600
B. -13.50 .. 20/2000
A. -15.00 .. 20/2400
B. -16.50 .. 20/2800
A. -18.00 .. 20/3200
B. -20.25 .. 20/4000
It becomes quite silly and moot past 20/4000
so I havent bothered doing the math past that.


From my research, I came with this. I know diopters are usually rounded to .25 but here I did the math to the hundreth. This results are also an aproximation, each eye is different. Someone with about -1.5 diopters might see 20/50, others may have a hard time seeing 20/100.


There are other factors besides myopia and also the lighting is important. Outside in daylight or indoors in very bright light, your pupil constricts and this acts as a pinhole effect. I am -5 and can barely see the 20/400, there are some days where I actually cant quite see if if my eyes are tired, its dark, my pupils are huge. However outside in broad daylight I can easily see the 20/200 E. For this reasons of course optomologists test your vision in a dimly lit room and use a projector to project letters, sometimes using mirrors if the room is small.

Note that the higher your myopia, the less likley you are correctable to 20/20 with anything, glasses(compenstation for minification even)RGP contacts, surgury because high myopes have stretched, thinned retinas which degrade. They also experience other problems(macular degradation, floaters, high order abreviations, etc). My diopter charts above take into account BCVA of 20/20 which of course gets increasingly less likley the higher your myopia is. If you are -12 and not correctable to 20/20, not even with RGP contacts, then youll be worse than 20/1600. I have used an expotentional scale that follows a pattern. It does become somewhat of a moot point worse than 20/400 since few eyecharts have larger letters than that(it becomes CF then HM) and you wouldnt want to go around uncorrected with such a large refractive error either.

The chart generally shows the maximum diopters you can still see a certain line. You can see the first few diopters dont make that much a difference but starting at -5.33 its 20/400 and for every 50% increase in diopters you can see that line from 50% of the distance. So a -8 would see the 20/400 line from 10 feet(10/400), therefore 20/800 from the normal 20 feet. The chart follows a pattern where 1.5x the diopters results in .5x visual accuracy.

However in reality, its often worse the higher the myopia due to retina degradation and your UCVA and BCVA would also drop below the .5x accuracy. Someone who is -8 could be 20/800 uncorrected, 20/20 with contacts. Take someone whos -27 he is likley to be worse than 20/6400 because he is not likley to be corrected anywhere near 20/20. If we give him RGP contacts to correct -19 diopters he will be -8 but perhaps 20/1000 and perhaps 20/40(or worse depending)with RGP contacts that fully correct him. Glasses would give him 20/60 due to minification, if we compenstate for this, it comes out to be about 20/40. This means the 20/60 line he sees is the same size as the 20/40 line without minification.

Last edited by Myope5, 11/11/2005, 2:29 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


http://www.lpf.com/source/rk/20something.html


In Diopters 20/something
-0.50 20/25 to 20/30
-1.00 20/30 to 20/50
-3.00 20/300
-4.00 20/400
-5.00 20/600
-6.00 20/800


Thats why being minus half diopter is so mild its not really considered a vision impairment and one shouldnt be labled as a myope if they arent over minus half diopter. Minus one diopter is very low myopia and you probably shouldnt bother with glasses in my opinion. The higher numbers show what youd be able to easily see on a bad day when your eyes are tired. Most people should be seeing 20/200 at -3, actually 20/150 if BCVA of 20/20 and on a good day.

20/800 is the largest letter ive heard of at the optometrist's room/office. Many charts only go up to 20/200 to 20/400. There is CF(count fingers) and HM(hand movement) for quick approximations if you can not see the top line on an eyechart. You could always make your own letters but they become absolutely huge past 20/400. I have a 20/1600 letter I made myself thats 27.2" big!
For those who dont want to bother, you could always just guessimate your 20/something(use my diopter chart as a guide) or use CF and HM.

CF(count fingers) corresponds to 20/200 if you can count them at 20 feet. Ditto to the big "E" on snellen charts. If you cant see at 20 feet, move closer.

CF 20' equals 20/200
CF 16' equals 20/250
CF 13.3' equals 20/300
CF 10' equals 20/400
CF 8' equals 20/500
CF 6.7' equals 20/600
CF 5' equals 20/800
CF 4' equals 20/1000
CF 3.3' equals 20/1200
CF 2.5' equals 20/1600
CF 2' equals 20/2000

HM(hand movement) corresponds to 20/2000 if you can see them at 20 feet. This means being able to see when someone is waving at you! We are talking about truly lousy vision here, 10x worse than CF! Simple math too.


HM 20' equals 20/2000
HM 16' equals 20/2500
HM 13.3' equals 20/3000
HM 10' equals 20/4000
HM 8' equals 20/5000
HM 6.7' equals 20/6000
HM 5' equals 20/8000
HM 4' equals 20/10000
HM 3.3' equals 20/12000
HM 2.5' equals 20/16000
HM 2' equals 20/20000



Last edited by Myope5, 8/4/2005, 4:39 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I have revised the chart a bit: Those charts show what diopter corresponds to how well you can barely see on the snellen. It does not take into account anything else but simple myopia. No astigmistim, no cateracts, no lazy eye, no diseases. Basically take a perfect 20/20 case and add just myopia to it. My results below are a little less due to the low amounts of astigmistim I have, both regular and irregular as well as other higher order abberivations. I dont have a chart for astigmistim since there are many variables depending on the angle of it. It tends to make u see double, you may see 20/40 fine but its doubled. Smaller letters may be ilegable due to doubling. The chart is for uncorrected vision too.


Someone of say -3 uncorrected will of course see better than someone thats -6 wearing -3 glasses who in turn will see better than a -15 wearing his old -12 glasses. They minify and disort what you see. Contacts dont minify as much but they tend to produce some glare and right after you blink, a fishbowl effect since your tears cling to your contacts briefly
so its like your looking thru a thin layer of water. Contacts do allow high myopes to see better due to less minification


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



-0.7 20/30 .51/1,32 near perfect vision
-1.05 20/40 .68/1.76 driving legal, forget glasses
-1.58 20/60 1.02/2.64 might need driving glasses
-2.37 20/100 1.7/4.4 need glasses part time
-3.55 20/200 3.4/8.8 need glasses more time
-5.33 20/400 6.8/17.6 need glasses full time
-8 20/800 13.6/35.2 can count fingers from 5 feet
-12 20/1600 27.2/70.4 can barely see and count own fingers
-18 20/3200 54.4(4.5)/140.8 20/40 with glasses
-27 20/6400 108.8 (9.1)/281.6 20/70 with glasses
-40.5 20/12800 217.6(18.1)/563.2 20/150 with glasses
-60.75 20/25600 435.2(36.3)/1126.4 legally blind with glasses


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)



I also added the example for my eyes. Its different depending on the person and also on pupil size, lighting and even intepretation of the blur. 20/20 is perfect vision but my eyes arent close to perfect but with best correction I get near perfect vison. I can read all of the 20/30, its sharp. On good days I can kinda make out a couple of the 20/25. My vision is equal or better than -5 now due to eye exercising. I am getting to the point where I can just barely make out the 20/300 line when I wake up and do a bit of palming. Using the near test, I read clearly to 21cm so this is -4.75 diopters emoticon I test my finding with -4.25 glasses and the 20/50 line is quite easy to read and I can kinda make out the 20/40 so this means I am 3/4 diopter undercorrected. When I use my -4.75 glasses the 20/40 line is easy to see.


My revised chart may be more accurate. Its based on someone that can easily see the 20/20 if plano. Of course if hes 20/30 plano then he will be a little worse than the above estimates(by .5 to .75). This is also based indoors with medium pupils. Outdoors or in otherwise bright lighting will constrict your pupils and result in pinhole effects. I can see at least a line better this way and the 20/200 uncorrected outside is easy for me!


Heres one for diopters in the middle emoticon




A. -0.7 20/30
B. -0.88 20/35
A. -1.05 20/40
B. -1.32 20/50
A. -1.58 20/60
B. -1.98 20/80
Those are the lucky ones with low to very low myopia. Their dependance on glasses is minimal, if any. The first diopter makes distant objects just slightly blurry but doesnt limit them in any way except perhaps if they want to be a pilot. This is the group that doesnt need glasses and especially not contacts. Optometrists should ask "are you sure you still want glasses when you dont need them" In fact those guys often make their eyes worse by overwearing their glasses. Many of us first started off as a single diopter. The "doubles" those with two diopters only really need glasses for driving in 49 of 50 states(see that driving post)and to see stuff like the instructors lectures on the board(he should ask to sit in front of class)Overall he should limit the time he uses his glasses or risk making his vision worse.


A. -2.37 20/100
B. -2.96 20/150
A. -3.55 20/200
B. -4.44 20/300
A. -5.33 20/400
B. -6.67 20/600
Those have some myopia and may need glasses part or full time depending how bad. They can read and eat fine without glasses however. They do envy the low myopes who dont really need glasses. The "triples" those with three diopters might be in the unfortunate situation where they need glasses most of the time. Being that 20/150 is probably the very best they can see on snellen chart with some needing 20/200, they feel "limited" in functionality without glasses. They can read and eat fine without glasses but anything more than 13-14" starts becomming blurry. Those guys can benefit alot from natural vision improvement with just one diopter improvement meaning they now nearly eliminated their dependance on glasses, yet still have some myopia which helps keep them away from "readers" For those nonbelievers, Intacs can correct up to -3 which is what they are. They may be wise to opt for -2 Intacs instead and be 20/40 then which is driving legal and yet still be able to read, only needing reading glasses for fine print.


A. -8 20/800
B. -10 20/1200
A. -12 20/1600
B. -15 20/2400
A. -18 20/3200
B. -22.5 20/4800
A. -27 20/6400
B. -33.75 20/9600
A. -40.5 20/12800
B. -50.63 20/19200
A. -60.75 20/25600
The unfortunate ones with high to xtreme myopia. Those that fall in the high range generally wear glasses(good idea for bifocals or reduced power) for even reading as without them their near point is so little their nose may pratically be touching the page! The xtreme myopes might as well be blind without their glasses. They may even shower with their glasses, ive heard of cases like that. Others have learned to shower blind, eyes open or close wont make a difference. They then feel for their glasses on the counter after exiting the shower. This group benefits least from any type of vision improvement, many dont even bother since itll still be super blurry anyway. Some get lasik and are happy with a partial correction since it means thinner, lighter glasses for less minification and disortion and also they arent "blind" when they wake up, shower or look for their glasses.


Color chart gives you headach?


A. -0.7 ..... 20/30
B. -0.88 ... 20/35
A. -1.05 ... 20/40
B. -1.32 ... 20/50
A. -1.58 ... 20/60
B. -1.98 ... 20/80
A. -2.37 ... 20/100
B. -2.96 ... 20/150
A. -3.55 ... 20/200
B. -4.44 ... 20/300
A. -5.33 ... 20/400
B. -6.67 ... 20/600
A. -8 ........ 20/800
B. -10 ...... 20/1200
A. -12 ...... 20/1600
B. -15 ...... 20/2400
A. -18 ...... 20/3200
B. -22.5 ... 20/4800
A. -27 ...... 20/6400
B. -33.75.. 20/9600
A. -40.5 ... 20/12800
B. -50.63.. 20/19200
A. -60.75.. 20/25600


Last edited by Myope5, 11/3/2005, 7:47 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I have to update my own diopter chart. Some of you seem to be a bit confused. Those values apply if you are corrected to 20/20 with contacts. If were talking glasses, we must factor in minification and cancel this out Truth be told, even a 20/20 eye has very slight imperfecations. It is perfect enough that people generally refer to as "perfect vision" but the true limits is 20/5. You can have no myopia and still not be 20/20 or you can be 20/10. If your best vision is 20/40 and you dont have myopia then you have something else causing it to blur. Likewise someone whos 20/20 and if he has no myopia, he has very little causing blur.

Let me try to make it simple. Lets use 20/20 as a starting point. Someone whos best corrected vision is 20/40 has about 2 diopters of "blur" that glasses can NOT correct. Its called high order abberivations but sometimes simply irregular astigmistim.
astigmistim blurs about half as much as myopia blurs. Therefore someone who is 20/20 will not have the extra "blur" and if we add on -1 of myopia he will be 20/40 but glasses can correct this. Whats preventing him from getting better than 20/20 is he still has high order abberivations but less than the 20/40 guy. If we take the 20/5 as the ultimate limit where you have absolutely ZERO of any complex high order abberivations this is the ultimate limit of your eye. Then at this point your rentenia would limit you. The human has about 6 million cones, the eagle much more.

quoted from a website:

In a human, the fovea has 200,000 cones per millimeter, giving us wonderful vision. In the central fovea of an eagle there are about a MILLION cones per millimeter. That's about the same number of visual cells as the finest computer monitor has on its entire screen when set at its highest resolution. The resolution for a person would be similar to setting a computer's screen at a much lower resolution.






Image


This is what a human with 20/10 vision would see a dragonfly from a distance.


Image

same but an eagle with its 20/2 vision.


The 200,000 cone resolution per milimeter is enough to give a human 20/5 vision in theory. An eagle has 5 times the resolution so in theory it can get 20/1 vision! Nothing short of bionic eyes or something like genetic engineering by crossing eagle genes into humans can ever make a human better than 20/5. There is also research that the human brain itself may not be able to handle much better than 20/5. Its like trying to tell someone to multiply 83638363 by 93736383 in 10 seconds.


Therefore if someone is 20/10 he may have 1.5 diopters less high order abberivations than someone whos 20/20. Both may have no myopia. Add in .75 diopters of myopia which causes about as much blurring as 1.5 diopters high order abberivations and the 20/10 guy will be seeing 20/20 and while the 20/20 guy will be struggling to see 20/30.
I still have to do more experments on a diopter chart for better than 20/20 vision but a good estimate is -.25 myopia extra for 20/15, -.50 for 20/13, -.75 for 20/10, -1 for 20/8, -1.25 for 20/6 and -1.5 for 20/5
But of course better than 20/10 is so rare, especially if he uses glasses to correct so this is where we compenstate for minification. Say someone is -5.25 diopters and he can barely see the 20/300 this would mean hes 20/10 because a 20/20 cant be more than -4.5 to see 20/300. If we give him glasses, the 20/13 line would be the size of 20/11.8 and the 20/10 would be 20/9 which is just too small for him. His glasses made everything a little smaller so he just cant see the 20/10 line. Give him contacts and he will see the 20/10 line since it will be a little larger.

Last edited by Myope5, 7/13/2005, 6:19 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


diopter chart for 20/40


A. -0.7 ..... 20/70
B. -0.88 ... 20/80
A. -1.05 ... 20/90
B. -1.32 ... 20/100
A. -1.58 ... 20/120
B. -1.98 ... 20/160
A. -2.37 ... 20/200
B. -2.96 ... 20/250
A. -3.55 ... 20/300
B. -4.44 ... 20/400
A. -5.33 ... 20/600
B. -6.67 ... 20/800
A. -8 ........ 20/1000
B. -10 ...... 20/1400
A. -12 ...... 20/1900
who cares about the rest your vision
would be just horrible.



diopter chart for 20/30


A. -0.7 ..... 20/55
B. -0.88 ... 20/60
A. -1.05 ... 20/70
B. -1.32 ... 20/85
A. -1.58 ... 20/100
B. -1.98 ... 20/125
A. -2.37 ... 20/160
B. -2.96 ... 20/200
A. -3.55 ... 20/300
B. -4.44 ... 20/400
A. -5.33 ... 20/500
B. -6.67 ... 20/700
A. -8 ........ 20/1000
B. -10 ...... 20/1400
A. -12 ...... 20/1900
who cares about the rest your vision
would be just horrible.




diopter chart for 20/25


A. -0.7 ..... 20/45
B. -0.88 ... 20/55
A. -1.05 ... 20/60
B. -1.32 ... 20/70
A. -1.58 ... 20/85
B. -1.98 ... 20/100
A. -2.37 ... 20/140
B. -2.96 ... 20/200
A. -3.55 ... 20/250
B. -4.44 ... 20/350
A. -5.33 ... 20/500
B. -6.67 ... 20/700
A. -8 ........ 20/900
B. -10 ...... 20/1300
A. -12 ...... 20/1700
who cares about the rest your vision
would be just horrible.



diopter chart for 20/20


A. -0.7 ..... 20/30
B. -0.88 ... 20/35
A. -1.05 ... 20/40
B. -1.32 ... 20/50
A. -1.58 ... 20/60
B. -1.98 ... 20/80
A. -2.37 ... 20/100
B. -2.96 ... 20/150
A. -3.55 ... 20/200
B. -4.44 ... 20/300
A. -5.33 ... 20/400
B. -6.67 ... 20/600
A. -8 ........ 20/800
B. -10 ...... 20/1200
A. -12 ...... 20/1600
B. -15 ...... 20/2400
A. -18 ...... 20/3200
B. -22.5 ... 20/4800
A. -27 ...... 20/6400
B. -33.75.. 20/9600
A. -40.5 ... 20/12800
B. -50.63.. 20/19200
A. -60.75.. 20/25600
copy of diopter chart in posts above.


diopter chart for 20/15


A. -0.7 ..... 20/25
B. -0.88 ... 20/30
A. -1.05 ... 20/35
B. -1.32 ... 20/40
A. -1.58 ... 20/50
B. -1.98 ... 20/70
A. -2.37 ... 20/85
B. -2.96 ... 20/125
A. -3.55 ... 20/180
B. -4.44 ... 20/250
A. -5.33 ... 20/350
B. -6.67 ... 20/550
A. -8 ........ 20/800
B. -10 ...... 20/1200
A. -12 ...... 20/1600
any higher, refer to the 20/20 as the difference would be neglecable anyway.



diopter chart for 20/13


A. -0.7 ..... 20/20
B. -0.88 ... 20/25
A. -1.05 ... 20/30
B. -1.32 ... 20/35
A. -1.58 ... 20/40
B. -1.98 ... 20/50
A. -2.37 ... 20/75
B. -2.96 ... 20/120
A. -3.55 ... 20/160
B. -4.44 ... 20/250
A. -5.33 ... 20/350
B. -6.67 ... 20/500
A. -8 ........ 20/700
B. -10 ...... 20/1100
A. -12 ...... 20/1500

any higher, refer to the 20/20 as the difference would be neglecable anyway.


diopter chart for 20/10


A. -0.7 ..... 20/20
B. -0.88 ... 20/20
A. -1.05 ... 20/25
B. -1.32 ... 20/30
A. -1.58 ... 20/35
B. -1.98 ... 20/45
A. -2.37 ... 20/60
B. -2.96 ... 20/90
A. -3.55 ... 20/140
B. -4.44 ... 20/200
A. -5.33 ... 20/300
B. -6.67 ... 20/500
A. -8 ........ 20/700
B. -10 ...... 20/1000
A. -12 ...... 20/1400

any higher, refer to the 20/20 as the difference would be neglecable anyway.



diopter chart for 20/8


A. -0.7 ..... 20/15
B. -0.88 ... 20/20
A. -1.05 ... 20/20
B. -1.32 ... 20/25
A. -1.58 ... 20/30
B. -1.98 ... 20/40
A. -2.37 ... 20/50
B. -2.96 ... 20/80
A. -3.55 ... 20/120
B. -4.44 ... 20/180
A. -5.33 ... 20/300
B. -6.67 ... 20/450
A. -8 ........ 20/600
B. -10 ...... 20/1000
A. -12 ...... 20/1400

any higher, refer to the 20/20 as the difference would be neglecable anyway.

I did a little rounding on the higher numbers such as 20/300 instead of something odd like 20/273 LOL. The above charts are quite confusing and also because diopters are measured by .25 and not by .1 I will round everything in the next post


Last edited by Myope5, 7/13/2005, 7:23 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I will do rounding in this verson. This one applies if you are correctable 20/25 to 20/30
and is similar to what I see.


A. -0.75 .... 20/40
B. -1.00 .... 20/50
A. -1.25 .... 20/60
B. -1.50 .... 20/80
A. -1.75 .... 20/100
B. -2.00 .... 20/120
A. -2.25 .... 20/133
B. -2.50 .... 20/150
A. -3.00 .... 20/200
B. -3.50 .... 20/250
I wont bother with the math past that
since the difference is neglecable.


I will do rounding in this verson. This one applies if you are correctable 20/20


A. -0.75 .... 20/30
B. -1.00 .... 20/40
A. -1.25 .... 20/50
B. -1.50 .... 20/60
A. -1.75 .... 20/70
B. -2.00 .... 20/80
A. -2.25 .... 20/100
B. -2.50 .... 20/120
A. -3.00 .... 20/150
B. -3.50 .... 20/200
A. -4.00 .... 20/250
B. -4.50 .... 20/300
A. -5.25 .... 20/400
B. -6.00 .... 20/500
A. -6.50 .... 20/600
B. -7.25 .... 20/700
A. -8.00 .... 20/800
B. -9.00 .... 20/1000
A. -10.00 .. 20/1200
B. -11.00 .. 20/1400
A. -12.00 .. 20/1600
B. -13.50 .. 20/2000
A. -15.00 .. 20/2400
B. -16.50 .. 20/2800
A. -18.00 .. 20/3200
B. -20.25 .. 20/4000
It becomes quite silly and moot past 20/4000
so I havent bothered doing the math past that.


I will do rounding in this verson. This one applies if you are correctable 20/15


A. -0.75 .... 20/25
B. -1.00 .... 20/30
A. -1.25 .... 20/40
B. -1.50 .... 20/50
A. -1.75 .... 20/60
B. -2.00 .... 20/70
A. -2.25 .... 20/80
B. -2.50 .... 20/100
A. -3.00 .... 20/125
B. -3.50 .... 20/160
I wont bother with the math past that
since the difference is neglecable.


I will do rounding in this verson. This one applies if you are correctable 20/10 to 20/13


A. -0.75 .... 20/20
B. -1.00 .... 20/25
A. -1.25 .... 20/30
B. -1.50 .... 20/40
A. -1.75 .... 20/50
B. -2.00 .... 20/60
A. -2.25 .... 20/70
B. -2.50 .... 20/80
A. -3.00 .... 20/120
B. -3.50 .... 20/150
I wont bother with the math past that
since the difference is neglecable.


I will do rounding in this verson. This one applies if you are correctable 20/8 to 20/10


A. -0.75 .... 20/15
B. -1.00 .... 20/20
A. -1.25 .... 20/25
B. -1.50 .... 20/30
A. -1.75 .... 20/40
B. -2.00 .... 20/50
A. -2.25 .... 20/60
B. -2.50 .... 20/70
A. -3.00 .... 20/80
B. -3.50 .... 20/120
I wont bother with the math past that
since the difference is neglecable.


Its difficult to make a diopter chart because of how different people interpret the blur differently. Also someone's 20/20, 20/15 or even 20/10 may be different from another's. Case in point, almost everyone agrees that astigmatic blur is worse than myopic blur even if the visual accuracy is the same. The letters may exhabit ghosting, glare, fuziness, doubling and even trippling in the case of astigmistim(any type) while myopia has none of this except simple blurring where letters simply look "gray" and "faded" Objects lack details and have fuzzy edges.

Also there might be an element of "guessing" on letters. Case in my point when reading the 20/25 line with best correction I would not say im interpreting the blur since there simply is so little its neglectable. I would describe them more as "dot-like" where letters like G, D, O, C, Q all have a roundish appearence. They look very nearly the same. I would be able to tell you that I see different letters of a roundish porportion but if asked to identify each individual letter Ill just call them out, knowing im gonna miss some. I think we should redefine the diopter chart into three categories: "easy/effortless to see, some effort to see, just barely able to see"

For my case then with best correction the 20/50 is easy to see, the 20/40 fairly easy, the 20/30 using some effort and 20/25 barely able to see. Lets revisit the rounded verson diopter chart that takes into account 20/20 best corrected. To easily see a letter, it needs to be 50% to 100% larger than the letter you can barely see. Some effort is needed for letters 25% to 50% larger. If you can barely see the 20/100 line then the 20/125 to 20/150 line takes some effort, while the 20/150 to 20/200 line is easy to see and lines 20/200 or larger of course is just effortless. (Barely)(some effort)(easy)

A. -0.75 .... (20/30)(20/40)(20/50)
B. -1.00 .... (20/40)(20/50)(20/60)
A. -1.25 .... (20/50)(20/60)(20/80)
B. -1.50 .... (20/60)(20/80)(20/100)
A. -1.75 .... (20/70)(20/100)(20/150)
B. -2.00 .... (20/80)(20/120)(20/200)
A. -2.25 .... (20/100)(20/150)(20/200)
B. -2.50 .... (20/120)(20/200)(20/250)
A. -3.00 .... (20/150)(20/250)(20/300)
B. -3.50 .... (20/200)(20/300)(20/400)
A. -4.00 .... (20/250)(20/400)(20/500)
B. -4.50 .... (20/300)(20/500)(20/600)
A. -5.25 .... (20/400)(20/600)(20/800)
B. -6.00 .... (20/500)(20/700)(20/900)
A. -6.50 .... (20/600)(20/800)(20/1000)
B. -7.25 .... (20/700)(20/1000)(20/1200)
A. -8.00 .... (20/800)(20/1200)(20/1500)
B. -9.00 .... (20/1000)(20/1400)(20/2000)
A. -10.00 .. (20/1200)(20/1600)(20/2400)
B. -11.00 .. (20/1400)(20/2000)(20/3000)
A. -12.00 .. (20/1600)(20/2400)(20/3500)

Any worse than a dozen diopters and the letters would have to be insanely large to be able to easily see them. I think it would just be easier to leave your glasses on alltogether emoticon
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


To clear more confusion about the diopter chart, for every 50% increase in diopters, you see 50% as good. This starts at about 20/100 though. If you recall from my diopter chart in the posts above, -2.25 is 20/100 then 50% more diopters makes it -3.50 and 20/200 then -5.25 and 20/400. Double the diopters would give you a little less than a third vision. This also starts at about -2 diopters or a bit more but -2 is a nice even number.

Take someone whos -2 he would barely see 20/80 if hes corrected to 20/20. Take a -3 and were talking 20/150. The -3 myope would see the 20/80 from about 10 feet(a bit more than that actually) or from 20 feet the letters need to be double in size. He would need to be half the distance of what a -2 could see. Take a -4 which is double of a -2 and that corresponds to 20/250 which is a bit less than a third as good as the -2 at 20/80. Another way to understand this is say someone who is -4 looks at a blurry car from 200 feet. Someone whos -6 would need to be 100 feet, else the car he sees from 200 feet would be twice as blurry. -9 and were talking 50 feet. -13.5 and that brings it down to just 25 feet. If a guy is double the -4 guy he would see the car from perhaps 60 feet at -8. Its basic math everyone can understand.


Add 50% the diopters=sees half as good(such as -4 to -6 20/250 becomes 20/500)
add 100% the diopters=sees a little less than a third as good(such as -4 to -8 20/250 becomes 20/800)


edit: reguarding contact lenses, they are NOT comparable to glasses. Just multiply your contact pescription by 1.25 to arrive at glasses. My diopter chart and all the formulas and explainations are based on your glasses pescription. Contacts sit directly on the eye and because of greatly reduced minification, they are more "effeciant" you need less pescription to achieve the same effects as glasses. -2 contacts is -2.5 glasses, -6 contacts is -7.5 glasses, etc its simple math emoticon

Last edited by Myope5, 7/21/2005, 1:30 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Image
-0.75 diopters for 20/30


Image
-1.00 diopters for 20/40


Image
-1.25 diopters for 20/50


Image
-1.75 diopters for 20/70

Image
-2.25 diopters for 20/100

Image
-3.50 diopters for 20/200

The charts above show what youd see with diopters of myopia. I have simulated the blur to portray various diopters. Below, I am making charts to simulate astigmastim. I dont really have a diopter chart for astigmastim because it varies quite a bit but take a best case scinerio, astigmastim blurs half as much as myopia. Hence 1.5 diopters of astigmastim is .75 of myopia. However astigmastim often blurs more than that. Not only that, astigmastim is much more annoying than myopia even if you see 20/50, the astigmatic victim would complain alot more than the myopic victim since the quality of vision with astigmastim is much poorer despite both having same snellen accuracy.The charts below show what youd see with diopters of astigmastim.


Image
1.50 diopters of astig for 20/30

Image
4.50 diopters of astig for 20/100

Image
3.00 diopters of irr. astig for 20/100

You can see that in best case, regular astigmastim blurs half as much as myopia but it does produce doubling which makes even 1.5 diopters very distracting since its both blurry and doubled from all distances making it hard to also read. astigmastim is really evil! At least with myopia things arent doubled and also sharp from near! The bottom chart shows irregular astigmastim which blurs almost as much as myopia and doubles at more than one angel so glasses are largely useless for the irregular kind emoticon

edit: Those pictures are at 800x600 on my sharp 21" monitor. You may not be able to see with the same accuracy on smaller, inferior monitors or at high resolutions. For example, 20/50 may be 20/70 or even 20/100 on your monitor.

Last edited by Myope5, 7/23/2005, 2:21 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


more examples of diopters correlating to 20/something. The bold is my comments.

A nearsighted patient with seven diopters of myopia may return in three months with a quarter of a diopter of residual myopia.
Patients usually see 20/20 or 20/15 in these cases and would not realize any benefit by wearing such a weak pair of new glasses.
a quarter diopter is a nonissue. Thats usually not even a line of blur. However if you are borderline 20/20 for example, say you can see half of the 20/20 then you may see none with -.25 diopters. Someone who could easily see 20/20 would still see 20/20 but itll be a little blurry at -.25


Low myopia would be from zero to –2.00 Diopter (D) correction. People with this range of myopia would see pretty well without glasses, often passing motor vehicle vision standards without glasses.
My brother is -1.5 in the better eye and 20/60 without glasses. He finds that he does not need glasses 95% of the time. He does sometimes wear glasses when driving for good measure and also if he sits in the back of the class. Its when you are more than -2d and 20/100(or worse) do you start to become more dependant on glasses


There is a very rough correlation between ammetropia and VA. A person with a –5.00 D correction for myopia will have a very poor uncorrected VA (UVA), somewhere in the neighborhood of 20/400.
accroding to my diopter chart, -5.25 is 20/400(if your BCVA is 20/20) so yes, this is accurate and a good approximation for most people. Some may be 20/300, others 20/500 depending on their BCVA


Just back from the laser eye doc. 20/25 and -.75 diopter in the right eye and 20/50 and -1.24 diopter in the left so I'm looking at a touch up job on the left. He actually wanted me to come in this Friday but I'm too chicken to just jump right in, even though I've done it before. So Aug. 28th I go under the knife and laser in hopes of one eye turning out 20/20. He won't do the right again cuz its too close to perfect and it could overcorrect.
He should easily achieve 20/20 if he ends up within half a diopter off and possibily 20/15 if dead on plano. His better eye is barely myopic and im in agreement he should well enough leave that one alone. He could always do eye exercises or if lazy, -.75 glasses(gonna be hard to convince the optometrist though!) and be 20/15 in that right eye. He has a mild form of monovision which will delay his need for reading glasses and also reduce his dependancy on them.


Regardless of how many residual diopters of nearsightedness are left to allow for the monovision, the vision on the eyechart can NOT be predicted just by looking at this number. There is no conversion between diopters and visual acuity on the eyechart (20/20, 20/30, etc.). In other words, if you are left with -1.50 diopters of residual nearsightedness you may see 20/40 with that eye in the distance, or you may see 20/100, 20/80 or 20/50. We cannot predict. It can be and is different for different people.
Im in agreement. Your BCVA plays the biggest factor. Other factors could be lighting such as if its unusually dim, the quality of the eyechart, is the printed letters robust and black or is it a crappy eyechart with cheap ink that has faded gray and peeling? Some people interpret the blur better or worse than others such as "is this an O or a D" If you are tired, nervous or have a headache or just "bad eye day" you may score worse on the snellen. My diopter chart is an average estimate of what youd see. -1.5 for me is 20/80 but its 20/60 for my brother. In my vision improvement book there are several people who improved to -1.5 diopters and are seeing 20/40 too and no longer need glasses.


Q6. During my FC1 my vision was 20/50 but my refractive error was -1.75. I was wondering first if this will DQ me and second if waivers are ever granted for refractive error if you meet acuity standards but not refractive standards and if they are how hard is it to get an ETP.

A. Refractive error is out of standards, but only by 0.25 diopters. This is DQ, however. It would require an exception to policy and not a waiver. It is really hard to predict ETP likelihood, but with it so close and the acuity within standards, you might get lucky.
Pilots must be 20/50 and -1.5 diopters or better. He has good accuracy for being -1.75 this puts my estimates that hes correctable to 20/13 so perhaps he may still pass


Q10. In the AFI148-123 14Nov2000 it states that for UPT flying class I one must have 20/70 Uncorrected distance vision and no more than -1.5 refraction. As I understand it one must meet Class I standards to get into UPT. Currently my right eye needs -2.75 and left -2.5 correction. As far as the 20/70 line I can get about 50% of the letters right. On the civilian side I have about 800hrs flight time along with my single/multi engine commercial instrument ratings along with CFI, CFII, and MEI, which means I can teach others to fly. Looking at class II requirements the max refraction is -4.0 and 20/400. I definitely meet class II requirements. My question is it possible/likely that I might get some sort of waver to the class I requirements to gain eligibility to UPT? I should also mention that I have 5 years in the Army reserves at E-5 and am currently 24 years old.

A. I hate to have to be the bearer of bad news, but this is outside the medical waiver process. You do not meet standards for FCI and need to apply for an exception to policy, not a medical waiver. The approval authority for exception to policy for vision and refraction standards for UFT is the Chief of Staff of the Air Force. (AFI 48-123 A7.7, Note 10).
-2.5 diopters and he can see half of the 20/70 line is just amazing! This would mean he can see more than 2/3 of the 20/80 line, making him "qualify" as a 20/80 accuracy. This would make him capable of 20/13 BCVA and 20/10 if his -2.75 eye can see as well without glasses as his -2.5 eye! Thats just amazing to come think of it when I would be 20/150 to 20/200 with -2.5 to -2.75 diopters!


Can You Become a Fairfax County Animal Control Officer?

Uncorrected vision not worse than 4.0 diopters (approx. 20/200), provided that there has been at least three (3) months of success wearing soft contact lenses.
For me, -4 and I can barely see 20/300! Youd need to be correctable to better than 20/20 to see 20/200 with -4 diopters. Like -3 diopters is the worse that I can still barely see 20/200


Summary of the above results in order:

-.25 diopters=20/20
-.75 diopters=20/25
-1.5 diopters=20/40
-1.75 diopters=20/50
-2.5 diopters=20/70
-4 diopters=20/200


All the above results are better than indicated in my diopter chart for 20/20. Therefore they are better than 20/20 with glasses




Last edited by Myope5, 8/4/2005, 6:09 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


damn, now that is a post emoticon

I will have to carfully read this one before I respond... (but I will)
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