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


My eyes seemed like they were horrible, but apparently I'm right in the median at -3.5 diopters (20/400) in each eye.

(he got lasik and ended 20/20 in each eye, slightly better OU. He was 20/20 with glasses. Update:
I have almost 20/12.5 vision, but something still doesn't feel "right" -- I read the 20/16 line perfectly easily, but had to strain on the 12.5 line to get 4/5 right. But still, my objective vision is much better than my subjective vision. Dunno if that's just psychological or what. Got my post-op today. 20/10 in right eye, 20/16 in left eye. I feel like I can see the future.)


So what happens if your eyesight ranges above the capabilities of LASIK? An implantable lens called an IOL has recently been FDA approved for refraction up to -20 diopters (about 20/10,000 on vision charts).


My comments: Although nearly 20/8000 on my objective blur chart, that is a good estimate. The snellen letters would need to be a little over 14 feet at 20/10000!


If you already see very well with glasses or contacts, and see at least well enough to function reasonably well without them, then I would NOT get LASIK if I were you. Obviously, this cutoff point is subjective, and each person has to decide for himself if the expected improvement is worth the risk. I’d set a hard limit at 20/40 (the legal driving limit, representing, on average, -0.50D to -0.75D of spherical refractive error), and a softer limit at about -2.00D. Myopia this mild is very easily corrected with lightweight glasses or contact lenses. Of course, the presence of a lot of astigmatism changes things, but in the end, only you can decide if the risk is worth it.


my comments: I agree, no point in lasik for mild myopia. You can consider orthoK which works extremely well for light prescriptions and its effects stick for days. -.5 diopters is going to be better than 20/40 in healthy eyes.



Uncorrected vision, OD 20/100, OS 20/200.

Significant myopia was found, as well as astigmatism in each eye. Best corrected vision was 20/30-2 in the right eye, 20/40+ in the left with a -1.00-1.50x85 OD, and -1.75-1.25x95 refractions shown, OD and OS respectively.


my comments: Thats a spherical equivalent of -1.75 and -2.25 correctable at 20/30 to 20/40. If we use the objective blur formula and use thw 4x and 6x multiplier, we arrive at about 20/140 and 20/210 vision.


I tested my own vision again with +3.5, +3.5 and +1 together, +3.5 and +3.5 together. This simulates -8.5, -9.5 and -12! My natural prescription is about -5 in the worse left eye that I used to simulate. I see 13/400 which makes me 20/600. At -8.5 I see 12/800 which makes me about 20/1330 and compenstating for magnification, it comes out to 20/1420. Looking at the objective blur chart...-8.5.......20/1438 So this proves my blur chart is right! At -9.5 I get 10/800 and compenstating for magnification thats 20/1760. at -12 I get 14/1600 and compenstating for magnification I get 20/2740. update: simulated -6 for 14/600 which got me 20/874 compenstating for magnification.


comparsions between me and blur chart.

-5=20/600 vs. 20/511
take -.5 penelity for 20/25 BCVA=20/614
-6=20/874 vs. 20/727
take -.5 penelity for 20/25 BCVA=20/849
-8.5=20/1420 vs. 20/1438
-9.5=20/1760 vs. 20/1791
-12=20/2740 vs. 20/2846

I didnt take penelity for the high myopia simulations because I wanted to avoid this variable. I did not exactly measure the distance, I know how far give or take a few inches. The magnification calculations get tricky with two pairs of plus glasses due to vertex distance. Even the blur interpretion is subjective. I will do more testing with this, but the fact im extremely close, well within the margin of error confirms that my objective blur chart formula is correct and accurate emoticon


The second procedure is an accelerated Ortho-K treatment that rapidly returns a patient to functional, natural vision within a couple of days to a couple of weeks. This method is used for patients with mild to moderate myopia up to -4.50-5.00D. of correction with uncorrected vision of up to 20/400-500 acuity. Dr. Kearney uses his own lens design, the C.C.C. lens, which is a new multicontouring lens design that is now available to orthokeratologists.


My comments: agrees with objective blur chart.


A 31-year-old healthy woman had bilateral laser in situ keratomileusis (LASIK) 10 months ago. According to the patient's file, the preoperative refraction was approximately -5.75 -0.50 × 175 in the right eye and -5.25 -0.75 × 175 in the left eye. The best corrected visual acuity (BCVA) was 20/20 to 20/16 (after lasik----->)The UCVA is 20/50 in the right eye and 20/25 in the left eye and the BCVA, 20/16 with -1.00 -0.50 × 0 and 20/20 with -0.25 -0.25 × 10, respectively



OS: -6.00D, -1.50D
OD: -5.50D, -0.25D
OS: 20/1200*
OD: 20/1000
OU: 20/1000

*Beyond about 20/400, Snellen Acuity measurements are pretty meaningless. I gauged this based upon a homemade Snellen chart with some really huge letters.


Per my blur formula, he "should" measure at 20/600(actually about 20/650) in the better eye and near 20/1000 in the worse(about 20/950) His worse eye has a -6.75 spherical equivalent but based on his own snellen measure, his cylindar does not appear to contribuate much to blur in his own subjective measure.



A patient with a refractive error of 1 D will have approximately 20/40 vision, ... error of 2 D will result in vision ranging from 20/100 to 20/200.


My comments: Found this off a website that no longer exists. I agree with the -1 correlation to 20/40. They gave a broad range for -2, but I disagree that -2 is anywhere near 20/200. I would put the range more like 20/80 to 20/120.


I am a victim of near-sightedness. Myopic of 20/200. Perscription is about -2.0 or something.
P.S. my vision is corrected better then 20/20.
By the way im not getting any sort of laser surgery if I don't have to. It is permanent and I personally don't want anything removed from my eyeballs that will never grow back. It would weaken my eye structure.


My comments: He does not know his exact prescription, but im guessing hes -2.5 with some cylindar which would blur him worse than 20/100 and most eyecharts have nothing in between.


I wear soft contacts now and my vision prescription is -5.50 in my left eye and -5.25 in my right. Is there any other option for me besides PRK? With my prescription, it's probably around 20/600...20/700.


My comments: This ones tricky. His glasses prescription could be as low as -5.5 or as high as -7. The two arent directly comparable, however per my objective blur chart, -5.5=20/600 and -6.25=20/800 so depending on his glasses prescription, hes more likley to be about 20/800 and likley somewhat worse than 20/600.


If my vision is around 20/30-20/40
My eye exam about 3 weeks ago said I am -.75 in each eye which equates to around 20/40 so hopefully all goes well


My comments: He will have no problem seeing 20/40 and will see some or even all of the 20/30 line. He even said hes 20/30 to 20/40.



I spent $2500 for both eyes. I wore contacts wiith a prescription of -1.25 and -1.50. The best I could muster without the contacts was 20/70 and 20/100 for visual aquity. He got PRK and ended up 20/15!


My comments: This doesnt sound right and he should have better UCVA than this. If we assume vertex distance, he would be about -1.5 and -1.75 in glasses, in truth his worse eye between -1.75 and -2 but I rounded down.(better to undercorrect than overcorrect in my opinion)
And if he really is capable of 20/15, his UCVA should be 20/50 and 20/70 at worst.


most rx's over say -4.00 cant read the 20/400 letters w/o squinting.


*This is what one optometrist speaks from experience



you are not 20/200 with -7.50. again you are more like 20/1000.


*Optometrist's estimate. Pretty obvious how bad -7.5 is(I say about 20/1200)



I have a refraction of -6.75 sph -1.00 cyl in one eye and -5.25 sph -0.50 cyl in the other, yet have an uncorrected distant visual acuity of 20/200 (correctable to 20/12). I tend to leave optometrists shaking their heads, saying "that couldn't possibly be right", since most patients they see with that level of refractive error tend to have DVA's of 20/400 to 20/800.


My comment: Accroding to my objective blur chart, hes a -5.5 spherical equivalent in the better eye. Because of his superior BCVA of 20/12 *with* spectacle minification, that accounts for a one diopter bonus(well almost but close enough)so with the bonus, this puts the blur at barely 20/400. Several reasons arise why he is seeing twice as well. Squinting is the most likley case. Some people when they blink, do slowly so for a split second before the eye closes completely, see clearer for that instant. Other reasons could be the lighting is too bright causing the pupil to constrict and act like a pinhole. Perhaps he doesnt need this much minus or perhaps hes guessing, cheating, memorizing or even perhaps he has extremely good blur preception. I am in agreement that with a prescription that high, youd normally be at 20/600 with a "fair" test assessing your UCVA.

Last edited by Myope5, 7/25/2006, 6:29 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


http://la-sight.com/LS_commDetail.asp?index=0

While I already posted this lasik testimonals many posts back in this thread, I wish to elaborate the new results. There are over 200 results that show pre-lasik UCVA and post-lasik UCVA and the accompanying refraction. See my comments below. Educational read to better understand the correlation between diopters and 20/x



Right Eye Hand Motions 20/20
Left Eye Hand Motions 20/20+

 
Refraction
Before After
Right Eye -9.00 -1.25 x045 0.00 -0.25 x084
Left Eye -8.00 -2.50 x175 +0.25 -0.25 x082

My comments 20/1600 to 20/2000 UCVA is so poor, all she could see was a hand waving at her! Everything was just a bunch of watercolors!


Right Eye 20/80 20/15
Left Eye 20/80 20/15+

 
Refraction
Before After
Right Eye +2.00 -2.50 x 174 +0.25 -0.25 x 001
Left Eye +1.25 -1.25 x 007 0.00 -0.25 x 021


My comments I dont have a hyperopic diopter chart, but his UCVA should be better in the left eye given the lower prescription!



Right Eye Counts Fingers 20/20
Left Eye Counts Fingers 20/20

 
Refraction
 Before After
Right Eye -11.50 -0.50 x 016 0.00
Left Eye -11.00 -0.25 x 168 -0.25 sph
 

My comments He chose PRK rather than phakic IOLs. Hes lucky to achieve 20/20 with such a strong myopic prescription. We are talking an objective blur of 20/2500. This is so bad, he sees 20 feet what perfect vision sees half mile! He is -.25 in the left, not bad enough to blur any measurable amount.


-1.00 -0.50 x 154 for 20/40- distance, 20/20+ BCVA


My comments 20/18 BCVA x2.5 blur multiplier = 20/45


Right Eye 20/200 20/20
Left Eye 20/400 20/20

 
Refraction
 Before After
Right Eye -2.00 -0.50 x 105 0.00
Left Eye -3.00 -0.25 x 179 0.00 -0.25 x 005


My comments Where is the 20/300 line on his eyechart? For the matter, where are the needed lines between 20/100 and 20/200 as well as 20/200 and 20/400? He would have an objective blur of 20/120(right eye) and just shy of 20/200(left eye)


Right Eye 20/100 20/15
Left Eye 20/60 20/15

 
Refraction
 Before After
Right Eye -2.00 sphere 0.00
Left Eye -1.25 -0.50 x 85 0.00 -0.25 x 10


My comments Concides with my objective blur chart for 20/20 BCVA so im guessing she didnt have the right glasses/contacts *or* her blur interpretation wasnt so good.


Right Eye 20/400 20/20+
Left Eye 20/400 20/20+

 
Refraction
 Before After
Right Eye -5.00 -0.75 x 179 0.00
Left Eye -5.00 -1.00 x176 +0.25 sph
 

My comments Objective blur would put her at 20/600 so its likley she squinted or just assumed there was an "E" even though she could see just a blurry smudge.


Right Eye Counts Fingers 20/20
Left Eye 20/400 20/20-

 
Refraction
 Before After
Right Eye -3.00 -1.00 x084 0.00 -0.50 x108
Left Eye -2.00 -0.25


My comments He had mild cateracts which blurred in addition to his myopia. Got IOLs.


Right Eye Counts Fingers 20/15-
Left Eye Counts Fingers 20/15

 
Refraction
 Before After
Right Eye -4.25 0.00
Left Eye -4.00 -.25
 
My comments Should be able to see a blurry 20/400 "E" but after lasik hes 20/15 despite -.25 in one eye!


Right Eye 20/200 20/20
Left Eye 20/200 20/20

 
Refraction
 Before After
Right Eye -3.00 -0.50 x109 0.00 -0.25 x146
Left Eye -2.00 -1.00 x071 0.00


My comments Wheres the 20/150 line on his eyechart? Left eye is better than 20/200, right eye barely 20/200.



Right Eye 20/60- 20/15
Left Eye 20/70- 20/15+

 
Refraction
 Before After
Right Eye -1.25 -0.50 x176 0.00
Left Eye -2.00 -0.50 x005 0.00


My comments Lets see here. Left eye has better than 20/15, perhaps 20/12. Use 6x blur multiplier. Therefore we arrive at 20/72
Right eye we use 3x multiplier so he should be seeing 20/50, not a blurry 20/60!

Last edited by Myope5, 7/24/2006, 6:31 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Right Eye 20/400 20/15
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -2.75 -2.00 x 38 0.00
Left Eye -1.50 -2.00 x 131 0.00 -0.25 x 106
 

My comments


He should easily have seen 20/200 in the better eye!


Right Eye 20/70 not treated
Left Eye 20/70 20/20+

 
Refraction
 Before After
Right Eye -0.75 -1.25 x 88 not treated
Left Eye -0.75 -0.75 x 85 0.00
 

My comments spherical equivalent of about -1.25 so she should have been 20/50 or 20/60 at worst.


Right Eye 20/200 20/20+
Left Eye 20/200 20/15

 
Refraction
 Before After
Right Eye -1.75 -0.50 x 90 0.00 -0.25 x137
Left Eye -1.75 -1.00 x 91 0.00


My comments should read 20/100 without much difficulty based on prescription and 20/15 BCVA.



Right Eye 20/150 20/10
Left Eye 20/150 20/15

 
Refraction
 Before After
Right Eye -1.75 0.00
Left Eye -2.00 0.00



My comments Should be nowhere near that bad. If hes really capable of 20/10 then -1.75 blurs 4x to 20/40!


Right Eye 20/400 20/15
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -2.00 -0.50 x168 0.00
Left Eye -2.00 -0.25 x006 0.00 -0.25 x73
 

My comments Should be way, way better than 20/400. Clearly he wasnt even trying otherwise he would see 20/200 piece of cake and even 20/100 with some effort. All normal healthy eyes correctable to 20/20 or better will easily see 20/200 at -2 and 20/100 with some effort.


Right Eye 20/400 20/20+
Left Eye 20/400 20/20

 
Refraction
 Before After
Right Eye -4.50 -0.75 x136 +0.25
Left Eye -4.50 -0.50 x101 +0.25 -0.25 106


My comments See what I mean? -4.5 is the limit for 20/400 per my objective blur chart. The guy above at -2 is way better than 20/400.



Right Eye 20/200 20/15
Left Eye 20/200 20/15

 
Refraction
 Before After
Right Eye -3.25 -1.00 x 167 0.00
Left Eye -3.75 -0.50 x 005 0.00 -0.25 x 70



My comments really pushing it, she may have squinted a little. Id consider her closer to 20/250 to 20/300.



Right Eye 20/400 20/15
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -3.25 -1.00 x176 0.00 -0.25 x 171
Left Eye -2.50 -1.00 x 29 0.00



My comments Should be 20/300(right eye) and 20/200(left eye) if not somewhat better.



Right Eye 20/400 20/20
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -3.50 -1.25 x 86 0.00
Left Eye -5.00 -0.75 x 102 -0.25


My comments Left eye has better BCVA so he still sees 20/400 with more myopia.


Right Eye 20/200 20/15
Left Eye 20/200 20/20

 
Refraction
 Before After
Right Eye -2.50 -0.50 x 111 +0.25 -0.50 x 24
Left Eye -3.50 -0.25 x 115 0.00 - 0.50 x 152


My comments Barely 20/200 in left eye but gets .5 diopter bonus due to 20/15 BCVA. So this is equal to -3 and 20/20 BCVA for 20/200 UCVA.



Right Eye 20/200 20/15
Left Eye 20/30 N/A (no surgery)

 
Refraction
 Before After
Right Eye -2.75 -0.50 x 180 0.00
Left Eye -0.75 - 0.50 x 10 N/A (no surgery)


My comments -3 spherical equivalent in right eye, should be good enough for barely 20/150. Left eye barely had any refractive error so lasik wasnt warranted. -1 spherical equivalent blurs 20/15 into 20/30
 



You may read the rest of the testimonals yourself, I have commented on plenty. I will give the average tally after I am done reading them all.

Last edited by Myope5, 7/30/2006, 12:39 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I found another very interesting correlation!


Right Eye 20/400 20/15
Left Eye 20/25- N/A (no surgery)

 
Refraction
 Before After
Right Eye -2.50 -0.50 x 114 0.00
Left Eye -0.75 -0.50 x 49 same
 

My comments Her surgeon wisely suggested she leave her good eye well enough alone because it didnt need correction and also to ward off reading glasses. Thats some good BCVA for a -1 spherical equivalent, but she may have had a 20/13 BCVA and -1 would blur to 20/26, hence the 20/25- as theres no 20/26 line and she may have missed one or two on the 20/25 line. I however am supprised why her bad right eye isnt capable of easily seeing 20/200, in fact my math tells me she should be capable of 20/130, making the 20/150 line readable without much difficulty.


Right Eye 20/100 20/15
Left Eye 20/100 20/15+

 
Refraction
 Before After
Right Eye -2.50 -0.25 x140 0.00
Left Eye -2.25 -0.25 x 15 0.00
 
My comments 2.5 diopters uses the 7x multi and if his BCVA is 20/15 or a hint better like 20/14.5, this comes out to just over 20/100 so he would see 20/100 but just barely.


Right Eye 20/100- 20/15
Left Eye 20/80- 20/15

 
Refraction
 Before After
Right Eye -2.25 sph 0.00
Left Eye -2.25 sph 0.00


My comments Very odd, one look and you can see why. Same refraction, same BCVA, different UCVA? I am gonna assume he was squinting a little in one eye or just got tired of straining to read the blurry 20/80 line and didnt try on the other eye. 6x multi makes it 20/90 which falls between 80 and 100, hmmm.


update: Found out he has significent aberrations in the right eye and a slight corneal distortion which wavefront lasik fixed. I have a similar problem in my own right eye that makes my BCVA less and I can tell its not perfectly clear. Still I wouldnt risk lasik on myself as my better left eye is dormant and sees fine.


Right Eye 20/80 20/15
Left Eye 20/150 20/20

 
Refraction
 Before After
Right Eye -2.25 -1.25 x131 0.00
Left Eye -2.75 -1.50 x 28 +0.25 -0.25 x117
 

My comments -2.75 and -3.5 spherical equivalent. Right eye would be 20/130, left eye would be 20/250. Reason is she squinted. Her picture was shown on the lasik website and shes asian with narrow beady eyes.


Right Eye 20/400 20/15
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -2.50 -1.25 x141 0.00
Left Eye -2.50 -1.25 x 59 0.00 -0.25 x 37


My comments spherical equivalent of -3 so he should see 20/150 and if not, 20/200 with relative ease. His eyechart had no 20/300 line.


Right Eye 20/70 20/20+
Left Eye 20/70 20/15

 
Refraction
 Before After
Right Eye -0.25 -2.50 x 11 0.00
Left Eye 0.00 -2.25 x 02 0.00 -0.25 x 88



My comments Heres a rare cylindar script. Take the spherical equivalent and we get -1.25 but I guess the distortions with cylindar can be tricky to interpret when reading a snellen



Right Eye 20/200 20/20+
Left Eye 20/400 20/20

 
Refraction
 Before After
Right Eye -3.50 -1.25 x 125 0.00 -0.25 x 160
Left Eye -3.25 -0.25 x 54 +0.50 - 0.25 x 60


My comments Looks like the staff who put up his report mistyped "200" instead of "400" for the worse right eye.
 

Right Eye 20/800 20/25
Left Eye 20/800 20/20

 
Refraction
 Before After
Right Eye -4.00 sph -0.25
Left Eye -4.00–0.25x015 0.00
 

My comments Poor blur preception and making little effort. This is evidenced by the person seeing only 20/25 at -.25


Right Eye 20/400 20/20
Left Eye 20/400 20/20

 
Refraction
 Before After
Right Eye -4.25 sph 0.00
Left Eye -4.25 sph 0.00
 

My comments perfect example



Right Eye 20/2000 20/25
Left Eye 20/2000 20/25

 
Refraction
 Before After
Right Eye -13.25 - 0.50 x 32 -0.25 - 0.75 x 115
Left Eye -12.25 - 0.50 x 97 -0.75 - 0.75 x 180
 

My comments Her surgeon just took the 20/2000 figure as an estimate. Funny because he took the same estimate for a -7 and 20/3000 for a -9! She would be 20/3000 at best. I am supprised shes 20/25 in both eyes now even though one has just over -1 spherical equivalent. Maybe she memorized that line with the better eye then recalled it with the worse!


Right Eye 20/800 20/25
Left Eye 20/1600 20/20

 
Refraction
 Before After
Right Eye -2.00 - 4.00 x 178 - 0.25 - 0.50 x 67
Left Eye -4.75 - 3.75 x 180 +0.37 - 0.75 x 144
 

My comments -4 and near -7 spherical equivalent. should be 20/400 and 20/1000 or so. I guess all that cylindar makes it hard to interpret blur.


Right Eye 20/1000 20/20
Left Eye 20/1000 20/20

 
Refraction
 Before After
Right Eye -4.00 - 0.75 x 180 0.00
Left Eye -3.75 -1.50 x 178 -0.25 sph
 

My comments Um no. Where did this 1000 get pulled from? She should be barely 20/400 accroding to my blur formula. 20/1000 isnt even close.


Right Eye 20/800 20/20
Left Eye 20/1000 20/20

 
Refraction
 Before After
Right Eye -8.00 - 1.50 x 015 0.00-
Left Eye -7.00 - 0.75 x160 +0.25 sph
 
My comments ill let you figure out whats wrong with this one.


Right Eye 20/800 20/20
Left Eye 20/800 20/20

 
Refraction
 Before After
Right Eye -6.50 - 0.25 x 10 -0.25 sph
Left Eye -4.50 - 0.75 x 11 0.00
 

My comments Looks like another estimate the doctor pulled when she couldnt see 20/400 in either eye. Her left eye should not be much worse than 20/400


Right Eye 20/800 20/25
Left Eye 20/800 20/20

 
Refraction
 Before After
Right Eye -7.75 – 0.25 x 026 -0.25
Left Eye -7.75 sphere (no astigmatiem) 0.00
 


My comments another estimate. I would place him at 20/1200 based on my formula


Right Eye 20/1200 20/15
Left Eye 20/1200 20/20

 
Refraction
 Before After
Right Eye -5.00 –0.50 x 157 -0.25
Left Eye -5.25 –0.25 x 122 0.25 –0.50 x 165
 

My comments isnt that funny her eyes are better than the other 20/800 estimates yet she was put down as 20/1200? I would say she can likley read the 20/600 line if there was one. Shes still 20/15 at -.25 which is proof that a quarter diopter has neglecable blur.


Right Eye 20/400 20/20
Left Eye 20/400 20/40

 
Refraction
 Before After
Right Eye -2.75 – 1.00 x 100 0.00
Left Eye -2.50 –0.75 x 084 -1.00
 

My comments Would be pushing it for 20/200, but should be doable in the left. Right eye would definately be 20/300 but his eyechart doesnt have that line. Big gap between 200 and 400. -1 for 20/40 concides with my diopter blur charts.


Right Eye 20/800 20/20
Left Eye 20/800 20/20

 
Refraction
 Before After
Right Eye -3.50 - 1.50 x 92 0.00
Left Eye -5.00 – 0.50 x 90 -0.25 sph
 

My comments I estimate 20/400 in the better eye, 20/600 in the worse.

Last edited by Myope5, 8/1/2006, 2:32 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


H.R is -1 sphere in left eye and 20/60

This is a fairly poor snellen score for only -1 and he corrects to 20/20! Perhaps he wasnt giving much effort as -1 is generally 20/40.


Right Eye 20/1000 20/20
Left Eye 20/1000 20/20

 
Refraction
 Before After
Right Eye -6.75 - 0.50 x 165 0.00 - 0.25 x 17
Left Eye -7.25 -1.25 x 004 +0.25 - 0.75 x 61
 


My comments Looks like an estimate was pulled out. It agrees spot on with my objective blur formula and chart for the right eye, but the left eye would be 20/1200



Right Eye 20/80 20/15
Left Eye 20/70 20/20

 
Refraction
 Before After
Right Eye -1.50 -0.50 x 009 -0.25 -0.25 x 166
Left Eye -1.25 -0.50 x 165 -0.25 -0.50 x 50



My comments Should be seeing a little better than this(see my blur multiplier) but is seeing well despite a minor residual prescription post lasik(which he didnt need in my opinion due to such a low script before lasik)


Right Eye 20/70 20/20
Left Eye 20/70 20/20

 
Refraction
 Before After
Right Eye -1.25 sphere 0.00
Left Eye -1.25 -0.25 x 142 0.00 -0.25 x 17


My comments At her age of 38, she traded up for readers. Should be seeing 20/50 or 20/60 at worst.


Right Eye 20/400 20/25
Left Eye 20/300 20/20

 
Refraction
 Before After
Right Eye -3.50 -0.50 x159 -0.75 -0.25 x 33 (target: -0.50)
Left Eye -2.75 -0.75 x 004 -0.50 (target: -0.75)
 

My comments Since when did his chart have a 20/300 line? I am gonna assume this to the fact she could see the 20/200 line from 13-14 feet. -3=20/300, -3.75=20/400 and after lasik -.75=20/25, -.5=20/20 So she has a 20/15 BCVA


Right Eye 20/800 20/20-
Left Eye 20/800 20/20

 
Refraction
 Before After
Right Eye -5.25 -0.25 x 03 -0.50 -0.50 x164
Left Eye -4.75 -1.00 x 05 0.00 -0.25 x 005
 

My comments -5.25 spherical equivalent may be able to see 20/600. I am assuming she stood closer to see the 20/400 E and the surgeon put her down for 20/800.


 Before After
Right Eye 20/60 20/15
Left Eye 20/60 20/15

 
Refraction
 Before After
Right Eye -1.25 – 0.25 x 155 0.00
Left Eye -1.25 – 0.25 x 015 0.00
 

My comments Should be seeing a little better than that, like 20/40 to 20/50


Right Eye 20/2000 20/30
Left Eye 20/2000 20/20

 
Refraction
 Before After
Right Eye -7.00 –2.25 x 175 -0.50
Left Eye -7.00 –2.50 x 002 0.00
 

My comments spherical equivalent of just over -8 corresponds to 20/1300. She probably count finger(CF) from 2' which corresponds to 20/2000. The fact she can only see 20/30 at -.5 means either she isnt trying or interprets blur poorly.


Right Eye 20/3000 20/25
Left Eye 20/3000 20/20

 
Refraction
 Before After
Right Eye -9.50–1.75x165 -0.25
Left Eye -10.25–1.75x180 0.00
 

My comments similar story to the above. Should be about 20/2400. No reason -.25 costs a line, if you check every other testimonal, many people see 20/20 with -.25 to -.5


Right Eye 20/400 20/40 (20/15 After Enhancement)
Left Eye 20/400 20/20

 
Refraction
 Before After
Right Eye -3.75 – 1.25 x 164 -1.00 sph (0.00 After Enhancement)
Left Eye -3.50 – 1.25 x 004 -0.25
 

My comments Shes a golfer so wanted the best distance vision. She needs readers but doesnt mind. She should still be 20/15 with -.25 and 20/30 at -1



Right Eye 20/800 20/20
Left Eye 20/1000 20/25

 
Refraction
 Before After
Right Eye -4.00 sphere 0.00
Left Eye -4.75 sphere -0.25 sphere
 

My comments another estimate that I disagree with. One lasik website did say -4 is 20/800 which you can see on page 5 of my thread.


Right Eye 20/1000 20/20
Left Eye 20/1000 20/20

 
Refraction
 Before After
Right Eye -3.25 - 1.50 x 003 0.00
Left Eye -3.50 - 2.00 x 160 - 0.25
 

My comments -4 and -4.5 spherical equivalent should be 20/400


Right Eye 20/400 20/15
Left Eye 20/4000 20/15

 
Refraction
 Before After
Right Eye -3.25 - 1.00 x 003 0.00
Left Eye -3.50 - 0.75 x 175 - 0.25
 

My comments obvious extra zero typo



Right Eye 20/1000 20/15
Left Eye 20/1000 20/15

 
Refraction
 Before After
Right Eye -3.25 - 1.00 x 003 0.00
Left Eye -3.50 - 0.75 x 175 - 0.25


My comments Bad estimate. She should be 20/300 or 20/400


Right Eye 20/800 20/15
Left Eye 20/800 20/15

 
Refraction
 Before After
Right Eye -4.00 - 0.25 x 097 0.00
Left Eye -3.25 - 0.25 x 115 0.00


My comments Ditto to the above.


Right Eye 20/800 20/15
Left Eye 20/600 20/15

 
Refraction
 Before After
Right Eye -6.50 -0.75 x 15 0.00
Left Eye -4.75 -0.75 x 11 0.00
 

My comments Good estimate.


Right Eye 20/800 20/20
Left Eye 20/800 20/15

 
Refraction
 Before After
Right Eye -2.25 - 0.75 x 079 0.00
Left Eye -2.25 - 0.50 x 73 0.00
 

My comments geez looks like they didnt even test his UCVA and just put a random snellen number. He might be able to resolve 20/100, if not, definately 20/150!


Right Eye 20/800 20/20
Left Eye 20/800 20/15

 
Refraction
 Before After
Right Eye -3.50-.50 x 45 0.00
Left Eye -2.50 sph 0.00
 

My comments Another gee wiz one.



Right Eye 20/800 20/15
Left Eye 20/800 20/15

 
Refraction
 Before After
Right Eye -3.75 - 0.75 x 008 0.00
Left Eye -3.50 - 0.50 x 75 0.00
 
 
My comments try 20/200


Right Eye 20/2000 20/20
Left Eye 20/2000 20/15

 
Refraction
 Before After
Right Eye -10.00 -0.50 x 06 +0.50
Left Eye -9.50 -1.00 x156 0.00
 

My comments my blur chart puts -10 at 20/2000 so this time the doctor got it right. His +.5 overcorrection wont go well with his presbyopia. If he accepts the risks, an enhancement can make his +.5 into -.5 to greatly improve his vision.


Right Eye 20/400 20/15
Left Eye 20/400 20/15

 
Refraction
 Before After
Right Eye -3.25 - 0.25 x 125 -0.12
Left Eye -4.00 - 0.25 x 28 -0.00
 

My comments The last one to finish things off. He should be 20/300 in the better eye, but as I said, his eyechart doesnt have that line


Last edited by Myope5, 8/2/2006, 10:43 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


Method of predicting visual acuity with change of spherocylindrical refractive error



Very interesting website that attempts to convert diopters to uncorrected visual acuity. You can see that with 6mm or larger pupils, the pinhole effect is greatly reduced. This is why eye exams should be done in a darkened room as ive mentioned before.

They came up with about 20/30 at -.5 which I disagree. Likewise for 20/50s for -1. The -2 results is pretty close and may be correct for some. Ditto with -3 although I believe -3 is easily twice as bad as -2. Their measure of -4 concides with mine at 20/334 but the gap between -3 and -4 is more than 1.5x, its about 1.7x and some say even 2x! They start to get too generous at -5 and following the pattern. They are too conservative for low diopters. -4 is where they are most accurate.



this guy below found it in a lasik book. I calculated it based on subjective blur, but will update it to reflect my objective blur in the second set of paranthesis

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)(20/25)


Low myopia
    -1.0 = 20/50(20/40)(20/40)
    -2.0 = 20/150(20/80)(20/100)
    -3.0 = 20/250(20/150)(20/200)
    -4.0 = 20/400(20/250)(20/334)


Moderate myopia
    -5.0 = 20/500(20/400)(20/500)
    -6.0 = 20/650(20/500)(20/800)
    -7.0 = 20/800(close enough)(20/1000)


Extreme myopia
    -8.0 = 20/1000(20/800?)(20/1300)
    -9.0 = 20/1300(20/1000?)(20/1600)



The -5 is the only one they got right. They are too conservative for low myopia and too generous for high myopia. One optometrist even said most figures or calculations tend to be conservative for low amounts, meaning they see better than what we think they do and too generous for high amounts meaning they see worse than the 20/800 or 20/1000 estimate thrown at very high myopes.


My Lenses are -2.5 so it will not affect me either way but my uncorrected vision is 20/50 which is pretty good. The funny thing is that I know a chap who's Lenses are -1.0 and -1.25 but his uncorrected vision is 20/100 which is way worse than mine, so it goes to show that the strength of your glasses is no indicator of how well you will see with out them or indeed how good your eyesight is anyway.


My comment: That -2.5 guy did not mention BCVA, but if his BCVA is at least 20/10, that explains it to a large extent. He would need to have a BCVA of 20/7 to go in line with my objective blur chart, -2.5 uses the 7x multiplier. Its more likley he has a BCVA of 20/12 to 20/15, is slightly overcorrected and is squinting a little. As for that 20/100 guy, I suspect he has subnormal BCVA, he has cylindar in addition to sphere(for some reason, some people omit or dont mention their cylindar, especially if its low like less than -1) another possibility is he is just not trying at all to interpret blur and only reading down as far as its easy. A normal, healthy eye correctable to 20/20 with -1 sphere, no cylindar should read at least 20/50 if not 20/40.


My eyesight was -6 diopters, or worse than 20/200 in both eyes. I could only read the E on the chart, but that's because I memorized it.


My comment: Most eyecharts have an "E" on top. Those who "pass" for 20/200 or 20/400 with unusually high prescriptions likley recalled it from memory and not actually "seeing" it which they cant. Someone who is honest and tries to actually see it without squinting or recalling from memory will find they wont be able to see 20/400 if they are much beyond -4. Random generator would be a great way to asset their UCVA by eliminating recall from memory. Thats what they may use for UCVA requirements to be a pilot or in some fields in the army. They even have categories called v1, v2, v3, v4, v5.



Technically, I fall into the "moderately myopic" category, since my distance correction is somewhere around a -4 in both eyes. (For those of you playing with decent eyes and who can't translate diopters, -4 in diopters translates to something like 20/400 vision, uncorrected.)


My comment: -4 is commonly associated with 20/400, some say worse than 20/400, others say its the limit for 20/400



Within each 1-D range of the spherical equivalent of the refractive error, the visual acuity spanned five to ten Snellen lines.
Within the narrow range of refraction between -2.00 and -2.50 D, the mean uncorrected visual acuity was 20/125 for 56 unoperated eyes and 20/63 for 29 operated eyes, a difference of three Snellen lines.


My comments: Makes no sense, nonsense. In fact its the courtesty or opposite from what ive seen, not so much in UCVA, but more to do with decreased quality. People after refractive surgury appear to be more picky with residual refractive error. I however agree with the 20/125 at -2 to -2.5 my blur chart shows 20/120 at -2.25 which is in the middle.


20/60 both eyes, just got -1 contacts on a whim the other day (makes reading signs 200 miles away a little easier) emoticon

only problem is they said they wouldn't do laser eye surgery on me because my vision isn't that bad. emoticon


My comment: He is lucky his surgeon is competent and has morals not to do lasik on someone that doesnt need it! He does not even need correction except for driving. If we are to assume -1 contacts equals -1.25 glasses, 20/60 sounds close enough



Q. What was your eyesight like before LASIK?

A. My vision was 20/400, which was enough to cause two of my female friends to clasp their hands and exclaim, "Wow, you're really bad!"

My prescription was -3 diopters (nearsighted), or close to that, with some astigmatism. I pretty much wore glasses almost all the time while I was awake.


My comment: The astigmatism potion is the real problem because he may not see perfectly clear even from near. Id much rather be alot more myopic and free of astigmatism then at least ill be in focus from near!



Last edited by Myope5, 8/5/2006, 1:02 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


The UCVA was 20/60 and manifest refraction was -1.75 D + 0.75 D at 55 producing 20/30.


My comments: spherical equivalent of -1.25 would decrease 20/30 into 20/75 so she must have good blur preception and/or squinted.


Update on my vision self-treatment experiment:

I had my annual medical exam today (for the local Sheriff's Office where I work, not for the FAA), and today's vision test results were as follows:

Refractive Error (Manifest): OS: –4.50 sph –0.50 cyl
OD: –3.75 sph –0.25 cyl
Distant Visual Acuity: OS: 20/200 (uncorrected), 20/10 (corrected)
OD: 20/100 (uncorrected), 20/10 (corrected)
OU: 20/70 (uncorrected), 20/10 (corrected)


My comments: Impossible unless he squinted or had the eye test in bright light. 20/10 BCVA is unusual(less than 2%) and gets a 1 diopter bonus. That still comes out to 20/170 and 20/300! I simulated -3.75 and I can barely see 20/400 in a fair test. Most people arent gonna see better than 20/300 with -3.75


An estimated 20 million adult Americans have mild nearsightedness (roughly speaking, 20/80 to 20/300 vision), which is the treatment range for Intacs. This range includes people requiring from -1.0 to -3.0 diopters of myopic correction. Intacs are designed especially for this group -- the
largest segment of nearsighted adults in the U.S.


My comments: Sorry but -1 is much better than 20/80. -3 and 20/200 sounds right.


[0012] If the retainer lens is discontinued for more than 12-24 hours, significant regression occurs in the corneal topography. For example, if the baseline myopia was -3 diopters (D), and the unaided visual acuity was 20/300, and after treatment, myopia was corrected to -0.50D and 20/20 WVA, if the retainer is worn each night or day, a 20/20-20/30 WVA, and less than -1 D myopia, can be maintained. If the patient does not wear the retainer lens for a minimum of 2 days and 2 nights, the UVA may regress to 20/100 -20/200, and the myopia may regress up to -2 D to 3 D.

My comments: OrthoK talk and how much it improves vision. -3 is quite bad being at 20/200 to 20/300 per the article.



Revisit of diopters to 20/x in my subjective testing, how well I see with the following prescriptions using various undercorrections with different minus powers. I tested mostly my dormant left eye which has 20/25 BCVA. The right eye with its 20/30 BCVA needs -.25 diopters less myopia to see the same line.


Left eye:

plano(needs -5 correction) 20/25
-.5 undercorrection 20/30
-.75 undercorrection 20/40
-1 undercorrection 20/50
-1.25 undercorrection 20/60
-1.5 undercorrection 20/80
-1.75 undercorrection 20/100
-2 undercorrection 20/120
-2.25 undercorrection 20/150
-2.5 undercorrection 20/200
-3 undercorrection 20/250
-3.25 undercorrection 20/300
-3.75 undercorrection 20/400
-4.75 undercorrection 20/600
-5(no correction) slightly below 20/600


The first half diopter blurs very little, only one line. The first diopter reduces my vision in half. It gets worse expotentionally from there. At -2 undercorrection, I definately cant see 20/100, the 20/200 is pretty easy to see still. At -2.5 the 20/200 is very blurry. The 20/300 is quite blurry and hard to see even at only -3. I cant quite make out 20/400 at -4 but at -3.5 to -3.75 I can but its very blurry. Its gradual where a quarter diopter makes only a tiny difference once I get to -3 and I have to decide how blurry is "too" blurry to actually "see" it and not just recall from memory. At -2.25, -3, -3.5 and -4.5 is where id say I would feel confident passing 20/200, 20/300, 20/400 and 20/600 every time. Ill keep up to date with more testing.

-2.25 for 20/200
-3 for 20/300
-3.5 for 20/400
-4.5 for 20/600


To further comment, my diopter charts and their corresponding 20/x are regarded as maximum values one can still just barely make out something. -4.5 has an objective blur of slightly worse than 20/400 so youd need a BCVA of marginally better than 20/20 to just barely discern 20/400. I did put down -4.5 and 20/400 in my rounded verson of the snellen as its closer than -4.25 and 20/375. -4.25 is slightly better than 20/400, -4.5 slightly worse with a 20/20 BCVA. Even though -4.5 is regarded as 20/400, this does not guarantee youll be able to discern 20/400. If not, youll of course be just slightly worse than 20/400. There is no such line as 20/450. You may be able to discern 20/400 with a -.25 lens that takes you down to -4.25

I can sometimes just barely discern 20/400 with a -4 undercorrection in the left eye but usually I need -3.75 and on bad days, -3.5! For someone with a 20/20 BCVA, he will be able to see 20/400 with -.5 diopters more myopia than me. Someone at 20/15 will be able to with -1 more myopia than me!


Last edited by Myope5, 8/10/2006, 10:45 pm
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


I heard somewhere the following value:

-.5 = 20/25
-1 = 20/50
-1.5 = 20/80
-2 = 20/120
-2.5 = 20/200
-3 = 20/300
-4 = 20/500
-5 = 20/800
-6 = 20/1200
-7 = 20/1800
-8 = 20/2700
-9 = 20/4000

My comments They believe each additional diopter results in 1.5x worse UCVA for the moderate and especially higher prescriptions.

Elsewhere, I heard this:

-1 = 20/40
-2 = 20/100
-3 = 20/200
-4 = 20/400
-5 = 20/600
-6 = 20/900
-7 = 20/1200
-8 = 20/1600
-9 = worse than 20/2000

My comments The closest in agreement to my objective blur chart and may in fact reflect the average values of UCVA for most myopes. I often use that chart for rounding and also to reflect more average UCVA rather than maximum values.

A third source said:

-1 = 20/50
-2 = 20/150
-3 = 20/300
-4 = 20/600
-5 = 20/1000
-6 = 20/1600
-7 = 20/2400

My comments Quite conservative, more so on the higher prescriptions

One lasik site said that:

-1.00 = 20/60
-2.00 = 20/200
-3.00 = 20/400
-4.00 = 20/800
-5.00 = 20/1,200
-6.00 = 20/2,000

My comments I already commented on this a few posts ago. Ill say again they are very conservative/strict, especially on the higher prescriptions.

My own objective blur chart:

-.5 = 20/25
-1 = 20/40
-1.5 = 20/60
-2 = 20/100
-2.5 = 20/150
-3 = 20/200
-4 = 20/300
-5 = 20/500
-6 = 20/700
-7 = 20/1000
-8 = worse than 20/1200

My comments This is my own rounded to snellen eyechart verson of the objective blur chart. -6 is actually 20/727 so the rounding to the nearest hundred is about 4% off which isnt all that much. There isnt a 20/700 on the snellen, but I put that number there for accuracy as it falls between 20/600 and 20/800. I did round off by 10% for -4, but in reality most -4's will probably not be able to see 20/300 snellen.


Overall, let me group the values together to make it easier to compare.

-1 values: 50, 40, 50, 60, 40
-2 values: 120, 100, 150, 200, 100
-3 values: 300, 200, 300, 400, 200
-4 values: 500, 400, 600, 800, 300
-5 values: 800, 600, 1000, 1200, 500
-6 values: 1200, 900, 1600, 2000, 700
-7 values: 1800, 1200, 2400, >2000, 1000
-8 values: 2700, 1600, >2400, >>2000, >1200


I am assuming they are taking 20/20 BCVA into factor. It appears the average for -1 is 20/50 with many capable of 20/40. It is clear(pun intended) that -1 does not result in much blur. For -2, we see(another pun) that the range is 20/100 to 20/200 with the average in between at 20/150. I have checked lots of websites and studies and nearly all of them have their own idea, that being 20/100 or 20/200 usually, some say 20/100 to 20/200, others say between 20/100 and 20/200. For -3, it appears to be twice as bad as -2 accroding to most sources. Some sources put -3 at a little more than twice as bad. By -4, I commonly see 20/400 associated with that amount of myopia. Ive seen several optometrists also say this. At -5, you most likley wont see 20/400 and be off the charts at most snellen charts. Going by the averages I listed, -5 appears quite bad, being between 20/600 and 20/800! -6 and up is high myopia and worse than 20/800 by those averages!

Summary of averages:

-1 = 20/50
-2 = 20/150
-3 = 20/300
-4 = 20/500
-5 = 20/800
-6 = worse than 20/800

Last edited by Myope5, 8/20/2006, 3:47 am
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Re: So how bad is -1 diopters? -2? -10? My eyechart research!


The below is someone's experience with Intacs(but anything that undercorrects will achieve the same end result be it glasses, lasik, orthoK, intacs)


Hi Molly, First of all, a 'plano', or zero
refraction is not required to have 20/20 or better vision.
For example, I am about -0.50 in my left eye, and see
20/15 with it.


My comments: Such a small residual myopia undercorrection does not have much affect on UCVA.
No one with a -.25 undercorrection will lose a line and this is comming from an optometrist's experience. -.5 diopters typically costs just one line so instead of 20/15 you may be 20/20 which is still considered perfect vision and nothing should be done but enjoy your crisp vision! I have tested my UCVA with my older glasses and found almost no difference with a slight undercorrection. But a slight undercorrection can help keep you out of readers without really making an impact on distance vision so its great! For this reason, an undercorrection with orthoK will pratically eliminate my dependency on glasses, period except maybe for driving.
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