HELP! WHAT IS 6/24 VISION?
Reggie Choo
I wear glasses with a power of 175 degrees and have an astig. of 25 degrees for both eyes.
Is my vision considered 6/24? If not, what is it and what is 6/24 in terms of degrees.
Would be grateful if someone can enlighten me.
Thanks,
Reggie
Rick Espinosa, O.D.
Reggie Choo <ru2b...@singnet.com.sg> wrote:
Reggie: 6/24 = 20/x
x = (20) (24)/6
x = 480/6 = 80
Therefore, 6/24 = 20/80.
Rick Espinosa, O.D., F.A.A.O.,
paul m. planer
Rick,
The 6/24 is probably referring to the european designation in
meters. 6 meters is approximately 20 feet (each meter is a bit
over three feet). So, to find out what the 6/24 is....multiply
both the numeratory and the denominator by 3 and you wind up with
18/72....round off to approximately 20/80.
Paul Planer,O.D.
Kip Bryan
Reggie -
I don't know what "power of 175 degrees" means. Perhaps your glasses
are
-1.75 diopters in power? Lens power is normally measured in diopters.
(Diopters = inverse of focal length of the lens in meters. Focal length
=
how far away from lens the image of something at infinity forms. Plus =
makes a real image (magnifying glass), minus = makes a 'virtual image'
on the same side of the lens as the something-at-infinity, so you look
thru
the lens to see the image. You can tell if your lens is plus or minus
by
moving it sideways: if objects move same direction, it's minus. Opposite
direction, plus.)
Metric measurements of acuity are normally 6/x, meaning
"you can see at 6 meters what normal eyes can see at x meters."
6/24 means "you need to be about 1/4 as far away to see the same stuff."
(Rick was just converting from metric to feet, above.)
Normal vision can see print when it is about 5 minutes of arc
(1/12 of 1 degree). For big enough distances, you can say that seeing
6/24 means you can see print that is 20 minutes of arc (1/3 degree)
or about 1 cm type at 1.9 meters away. The full moon is about 30
minutes.
If you're looking for a conversion between diopters of lens power and
visual acuity (20/20 or 6/6 sort of description) then I can't help you.
There isn't a definite relationship as it depends upon illumination and
the measurements of your eye (pupil size (& illumination),
cornea to lens, lens to retina, corneal curvature, etc.) If you were
able to compute the "Modulation Transfer Function" for your eye, then
you could perhaps say. (There are ways to measure the MTF of your eye.)
rji...@singnet.com.sg
Kip Bryan <ki...@world.std.com> wrote:
>Rick Espinosa, O.D. wrote:
>>
>> Reggie Choo <ru2b...@singnet.com.sg> wrote:
>>
>> >I wear glasses with a power of 175 degrees and have an astig. of 25 degrees for both eyes.
>> >Is my vision considered 6/24? If not, what is it and what is 6/24 in terms of degrees.
>> >Would be grateful if someone can enlighten me.
>> >Thanks,
>> >Reggie
>>
>> Reggie: 6/24 = 20/x
>> x = (20) (24)/6
>> x = 480/6 = 80
>>
>> Therefore, 6/24 = 20/80.
>>
>> Rick Espinosa, O.D., F.A.A.O.,
>Reggie -
>I don't know what "power of 175 degrees" means. Perhaps your glasses
>are
>-1.75 diopters in power? Lens power is normally measured in diopters.
>(Diopters = inverse of focal length of the lens in meters. Focal length
>=
Yes, you are spot on. Singaporeans have used this term 'degrees' to
mean dioptres X 100. Therefore -10.00 dioptres = -1000 degrees. I
don't know how this term got started, it has been with us ever since
I can remember. When a patient asks me what prescription I am
prescribing, I give my answer in Dioptres, however a good proportion
of them will ask me how much is that in degrees.
Roland J. Izaac
Raymond A. Chamberlin
rji...@singnet.com.sg wrote:
>
.................
>
>Yes, you are spot on. Singaporeans have used this term 'degrees' to
>mean dioptres X 100. Therefore -10.00 dioptres = -1000 degrees. I
>don't know how this term got started, it has been with us ever since
>I can remember. When a patient asks me what prescription I am
>prescribing, I give my answer in Dioptres, however a good proportion
>of them will ask me how much is that in degrees.
And I thought optometric terminology couldn't be worse than it is in
the U. S. Now you show me there are even worse degrees of it. I'm
glad my degrees are not in optometry. The methodology disagrees with
me--too many obtuse angles; however, I agree that -1000 deg is pretty
cool (far below absolute zero on any scale). ;-)
Ray
rji...@singnet.com.sg
>rji...@singnet.com.sg wrote:
>Ray
Sorry Ray, this is not an optometric terminology. This term is used
by the lay pereson.
Roland J. Izaac
Singapore
Raymond A. Chamberlin
rji...@singnet.com.sg wrote:
>
..................
>
>Sorry Ray, this is not an optometric terminology. This term is used
>by the lay pereson.
Hmmm. Interesting. On this side of the Pacific, the public shuts up
and the "experts" dump on them. I thought Singapore was where the law
got laid down and everybody accepted it or else! Guess the media are
pulling my leg again.
Ray