Diopters to Visual Acuity

[eyedoc]

Hello everyone!

I was wondering if someone could post a table of diopter power correlated to visual acuity (20/20, 20/100, 20/600, etc). Please post for PLUS power lenses, I will post one below I found online, it is for MINUS power lenses.

I understand that these are only approximations, and that's just fine.
My glasses are +11.00 OU, single vision and no astig. I know I'm off the charts, but I'm curions to learn my VA, unaided, given my prescription.

I also read that the chart for MINUS is not equivalent to a PLUS power. That is, if a person wearing a -5.00 has unaided VA of 20/500, this does not mean
that someone wearing a +5.00 will have unaided VA of 20/500 as well.

Is there a formula to estimate VA for PLUS power, given the diopter used?
Please post a chart like the one below, but for PLUS rx's.

Tnx

Refractive Error & Visual Acuity

Refractive Error

Myopia in Diopters

Approximage Unaided

Visual Acuity

—.50 D 20/50

—1.00 D 20/100

—2.00 D 20/200

—3.00 D 20/300

—4.00 D 20/400

—5.00 D 20/500

—6.00 D 20/600

—7.00 D 20/700

—8.00 D 20/800

—9.00 D 20/900

—10.00 D 20/1000

• These approximations apply to nearsighted (myopia) patients wearing glasses.

[Happylady]

Well, my prescription is about a -2.50 and I see about 20/100 without correction.

[walleye]

To find your VA without a low vision acuity chart put up the 20/400 E on the chart and see if you can see it at 20 feet. If you cannot, start walking toward the chart. If you can see the E at 10 feet you have 20/800 unaided visual acuity. If you see it between 20 feet and 10 feet you have around 20/600 vision.( Could be done on any distance as long as your projectochart is calibrated properly.
Unaided acuities of hyperopes vary widely due to the accommadation of the patient up to age 55 or so. After that it is more predictible but don't know the exact correlation. But it is much less that myopes. After 35 years of practicing one gets a feel for unaided acuities but is still surprised occasionally by how good or how poor a hyperope's acuity is-and also how they don't care!!

[eyedoc]

hi walleye,

what do u mean by...

"still surprised occasionally by how good or how poor a hyperope's acuity is-and also how they don't care!!"

i have like zero (0) accommodation, i guess it is due to the power of my +11.00 prescription, but i cannot manage to squint/accommodate to see not even bit better. and i'm only 31 years old.

when you say that:

"...but don't know the exact correlation. But it is much less that myopes."

do you mean that someone with a -11.00 prescription will have worse unaided VA than someone who uses +11.00 ??

thanks for taking the time to reply.

[walleye]

Some hyperopes come in with say 20/60 unaided acuity and say they never wear glasses to drive and don't want to even though I've prescribed them bifocals. They only wear glasses to read. And a myope will come in with 20/25 unaided acuity and complain of distance blur and will willingly wear an Rx full time!!

When you get up into the 11.00 diopter range both hyperope and myope acuities will be very bad. But I would say the myope will be worse.

But down into the say + or - 3.00 range a 3 dioper myope might have an unaided acuity of 20/300-20/400 but a 3 diopter hyperope may have and acuity of 20/100. The bottom line to your question is that the unaided acuity of myopes is more predicitible than that of hyperopes.

[Graduate]

Hello everyone!

I was wondering if someone could post a table of diopter power correlated to visual acuity (20/20, 20/100, 20/600, etc). Please post for PLUS power lenses, I will post one below I found online, it is for MINUS power lenses.

I understand that these are only approximations, and that's just fine.
My glasses are +11.00 OU, single vision and no astig. I know I'm off the charts, but I'm curions to learn my VA, unaided, given my prescription.

I also read that the chart for MINUS is not equivalent to a PLUS power. That is, if a person wearing a -5.00 has unaided VA of 20/500, this does not mean
that someone wearing a +5.00 will have unaided VA of 20/500 as well.

Is there a formula to estimate VA for PLUS power, given the diopter used?
Please post a chart like the one below, but for PLUS rx's.

Tnx

Refractive Error & Visual Acuity
Refractive Error
Myopia in Diopters
Approximage Unaided
Visual Acuity

—.50 D 20/50
—1.00 D 20/100
—2.00 D 20/200
—3.00 D 20/300
—4.00 D 20/400
—5.00 D 20/500
—6.00 D 20/600
—7.00 D 20/700
—8.00 D 20/800
—9.00 D 20/900
—10.00 D 20/1000

• These approximations apply to nearsighted (myopia) patients wearing glasses.

don't waste time on acuity/power estimation,half of time it will get you wrong estimation.

[chip anderson]

What difference does it make, if you can see well with your glasses? Unless of course you are trying to get into the Air Force as a pilot?

[wmcdonald]

Egger's Chart Logic

Do some research on the above subject and you will find that for every line above 20/20 towards the lower end of the Snellen Chart, you will be approximately 0.25D away from emmetropia. So if you saw 20/40 your ametropia would be approximately 0.75D. As we move up it increases to 0.50D per line. An example would be 20/200 and the ametropia will be approximately 3.50 to 4.00D. This information can be found in a number of texts, including Borish. It does not indicate hyperopia or myopia. In the early days of refraction all testing was done utilizing subjective techniques To test for ametropia a + lens was initially employed based roughly on the line on the Snellen Chart read by the patient. If it improved the acuity, then by golly we had a hyperope. If not, then we went in the other direction and refined from there. The process is interesting and I encourage you to look further to get additional clarification. Keep in mind you will have many indicate that they see x with whatever Rx.......the eye is organic in nature and not a static instrument so these are estimates only.

[Myoptic33]

diopters vs. 20/20

This topic comes again quite often and in many message boards. There are many factors determining your UCVA and pescription, too tired to list them all. Hyperopia is accomodated so they can use a cycoplegic refraction for that. The manifast refraction only reveals hyperopia not accomodated. An example is this 19 year old lady who was +6 diopters, she could accomodate +4 diopters so her manifast was +2 and her distance accuracy was 20/70 but her vision was more and more blurry the nearer she got. She would still be 20/70 with -2 myopia but her near vision would be perfect at 20" or half meter. Any closer depends how much she can accomodate and any further will gradually blur. The below are what youd see with the following diopters of myopia without astigmastim.

-.5 diopters of myopia is so little, its generally a nonissue that warrants no attention. It results in the loss of one line. 20/25 instead of 20/20, 20/30 instead of 20/25, etc.

-1 diopters results in half UCVA. You may be 20/40 correctable to 20/20 with glasses. I was 20/50 corrected to 20/25 with -1 glasses back when I was 12.

-2 diopters typically results in the neighboor of 20/100 vision but this is largely dependant on your BCVA. It can be better than 20/50 or worse than 20/200. Almost everyone can see the 20/200 easily and many can still make out the 20/100 with some effort. I fall in between at 20/150 with a -2 diopter undercorrection.

-3 diopters results in 20/200 for most people. There are a few who can make out 20/100 but they have very good BCVA. Those with BCVA's below 20/25 may not be able to see 20/200. Almost everyone can see the 20/300 quite easily though.

-4 diopters results in 20/300 for most people. Some can still discern 20/200 while others cant quite see 20/300.

-5 diopters will result in a blurry 20/400 for many. This is my pescription and I tested myself at 20/500.


summary:

-1 20/40
-2 20/100
-3 20/200
-4 20/300
-5 20/400 or worse.

20/400 is the largest E on many eyecharts. Past that, many consider it CF or count finger vision. My CF is 10'

[eyedoc]

What difference does it make, if you can see well with your glasses? Unless of course you are trying to get into the Air Force as a pilot?

chip,
knowledge - or estimate- of the answer to my question will not make any difference. just a bit to satisfy my curious appetite and thirst for knowledge.
:idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea:

[Darryl Meister]

Based upon various clinical studies, the visual acuity can be predicted from an absolute refractive error using the formula:

D = 10^(E / 2 + 1.25)

where D is the Snellen denominator in feet and E is the refractive error in diopters.

For instance, given a refractive error of 0.25 D,

D = 10^(0.25 / 2 + 1.25) = 10^1.375 = 23.7

Or, for a refractive error of 0.25 D, the visual acuity is roughly 20/25.

Of course, as mentioned earlier, a hyperope can compensate for some degree of refractive error, depending upon his or her reserve of accommodation (though this could put strain on the oculomotor system).

The size of the pupil, size of the object, and contrast of the object are just a few of the factors that can significantly impact visual acuity for a given refractive error (assuming that vision is otherwise healthy and normal).

[Myoptic33]

This forumula would make a -1.5 exactly 20/100, a -3 20/1000 and a -5.5 20/10000! Either im doing the math wrong or the forumla only works for very low amounts of myopia. I have come with my own formula and testing it with plus lenses to simulate more myopia, it appears to work with high accuracy. The formula of mine starts at -2 diopters. a 50%(1.5 times) increase in diopters results in 50%(half) visual accuracy. If someone whos -2 is seeing 20/80 and his eyes get worse to -3 or he wears +1 glasses his accuracy would drop to 20/160. -4.5 diopters would then result in 20/320.

[Darryl Meister]

Either im doing the math wrong or the forumla only works for very low amounts of myopia

Yes, this formula is a "best fit" model of measured visual acuity versus power error for a population of subjects. The study probably stopped around 3.00 or 4.00 D, so the formula will most likely break down beyond that. I probably should have made note of this, though judging refractive error from visual acuity beyond 3.00 D isn't really practical anyway, since few charts have lines above 20/200.

If someone whos -2 is seeing 20/80 and his eyes get worse to -3 or he wears +1 glasses his accuracy would drop to 20/160. -4.5 diopters would then result in 20/320

Keep in mind that his uncorrected acuity with a -2.00 D would be closer to 20/200, and that an additional 1.00 D of error would represent 50% more blur.

[Myoptic33]

Well, my prescription is about a -2.50 and I see about 20/100 without correction. This is what happylady(see above post) sees. I would think -2 is in the 20/70 to 20/100 range. In my vision book, this guy was seeing 20/70 with -2.5 glasses which correct to an amazing 20/15! Low myopia is less than -3 diopters and most people see 20/100 or better with a low amount of myopia. Of course as ive said, what your BCVA is affects your UCVA. I am not gonna see 20/100 with -2.5 diopters since my BCVA isnt 20/20. I would be between 20/100 and 20/200 and yes ive tested this out already with my -2.5 glasses I use for near work.

[Darryl Meister]

Nevertheless, in this particular controlled study under carefully chosen conditions, a typical observer demonstrated a visual acuity of around 20/300 with 2.50 D of error. Depending upon the ambient lighting, letter type, chart contrast, and several other optical and physiological factors (including your normal corrected acuity), you may do better or worse. Other charts based on different test criteria, for instance, may show an improved rating for 2.50 D of error.