Why don't ophthalmologists and optometrists use the Landolt C chart,instead of the Snellen chart?

#13 05-08-2008, 03:18 AM

Doug,

You are wearing a -11 diopter lens. Does that make the image
on your retina "smaller"??

And is that image seem sharper to you from your "smaller" image
produced
by you -11 diopter lens??

Enjoy,

On May 5, 8:49*pm, douglas <Protoman2...[at]gmail.com> wrote:
- quote -

> On May 5, 10:27*am, otisbr...[at]embarqmail.com wrote:
> > Subject: *Accuracy of measurement.
> > 1. Visual Acuity: *read Snellen where 3/8 inch letters are 20/20, and
> > 3/4 inch letters are 20/40.
> > 2. *Refractive STATE: *For that you will need plus and minus lenses
> > in
> > 1/4 diopter increments. *From 20/60 (let us say) you determine the
> > minimum minus required to just-clear the 3/8 inch line.
> > Judy> More accurate what? *Accuracy of determination of refractive
> > error is
> > not a function of the chart used.
> > Otis> You are correct. It is determined by the person using his
> > own "test" lenses to make an accurate measurement of his
> > refractive STATE.
> > Judy> *Best corrected acuity measurement
> > might be slightly more precise, but is of little practical benefit.
> > Otis> Best-Corrected value (can produce 20/10 vision) might mean
> > -1 to -1.5 diopters more minus.
> > Enjoy,
> > On May 4, 3:18*pm, Dr Judy <mpac...[at]rogers.com> wrote:
> > > On May 2, 1:53*pm, douglas <Protoman2...[at]gmail.com> wrote:
> > > > > > Why don't ophthalmologists and optometrists use the Landolt C chart,
> > > > > > instead of the Snellen chart? It's harder to cheat w/ the Landolt C.
> > > > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > > > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > > > precise results?
> > > More accurate what? *Accuracy of determination of refractive error is
> > > not a function of the chart used. *Best corrected acuity measurement
> > > might be slightly more precise, but is of little practical benefit.
> > > Some optometrists or ophthalmologists mihgt have a Landolt C, few will
> > > have a Bailey Lovie chart, so even if you ask, they are unlikely to be
> > > able to do it. *Researchers and low vision specialists are more likely
> > > to have a Bailey Lovie chart.
> > > Judy- Hide quoted text -
> > - Show quoted text -
> Making the image smaller somehow raises my acuity? That's a new one.
> YOUR RETINA IS NOT A COMPUTER SCREEN.- Hide quoted text -
> - Show quoted text -

#12 05-06-2008, 12:49 AM

On May 5, 10:27*am, otisbr...[at]embarqmail.com wrote:
- quote -

> Subject: *Accuracy of measurement.
> 1. Visual Acuity: *read Snellen where 3/8 inch letters are 20/20, and
> 3/4 inch letters are 20/40.
> 2. *Refractive STATE: *For that you will need plus and minus lenses
> in
> 1/4 diopter increments. *From 20/60 (let us say) you determine the
> minimum minus required to just-clear the 3/8 inch line.
> Judy> More accurate what? *Accuracy of determination of refractive
> error is
> not a function of the chart used.
> Otis> You are correct. It is determined by the person using his
> own "test" lenses to make an accurate measurement of his
> refractive STATE.
> Judy> *Best corrected acuity measurement
> might be slightly more precise, but is of little practical benefit.
> Otis> Best-Corrected value (can produce 20/10 vision) might mean
> -1 to -1.5 diopters more minus.
> Enjoy,
> On May 4, 3:18*pm, Dr Judy <mpac...[at]rogers.com> wrote:
> > On May 2, 1:53*pm, douglas <Protoman2...[at]gmail.com> wrote:
> > > > > Why don't ophthalmologists and optometrists use the Landolt C chart,
> > > > > instead of the Snellen chart? It's harder to cheat w/ the Landolt C.
> > > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > > precise results?
> > More accurate what? *Accuracy of determination of refractive error is
> > not a function of the chart used. *Best corrected acuity measurement
> > might be slightly more precise, but is of little practical benefit.
> > Some optometrists or ophthalmologists mihgt have a Landolt C, few will
> > have a Bailey Lovie chart, so even if you ask, they are unlikely to be
> > able to do it. *Researchers and low vision specialists are more likely
> > to have a Bailey Lovie chart.
> > Judy- Hide quoted text -
> - Show quoted text -

Making the image smaller somehow raises my acuity? That's a new one.
YOUR RETINA IS NOT A COMPUTER SCREEN.

#11 05-05-2008, 05:27 PM

Subject: Accuracy of measurement.

1. Visual Acuity: read Snellen where 3/8 inch letters are 20/20, and
3/4 inch letters are 20/40.

2. Refractive STATE: For that you will need plus and minus lenses
in
1/4 diopter increments. From 20/60 (let us say) you determine the
minimum minus required to just-clear the 3/8 inch line.

Judy> More accurate what? Accuracy of determination of refractive
error is
not a function of the chart used.

Otis> You are correct. It is determined by the person using his
own "test" lenses to make an accurate measurement of his
refractive STATE.

Judy> Best corrected acuity measurement
might be slightly more precise, but is of little practical benefit.

Otis> Best-Corrected value (can produce 20/10 vision) might mean
-1 to -1.5 diopters more minus.

Enjoy,

On May 4, 3:18*pm, Dr Judy <mpac...[at]rogers.com> wrote:
- quote -

> On May 2, 1:53*pm, douglas <Protoman2...[at]gmail.com> wrote:
> > > > Why don't ophthalmologists and optometrists use the Landolt C chart,
> > > > instead of the Snellen chart? It's harder to cheat w/ the Landolt C.
> > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > precise results?
> More accurate what? *Accuracy of determination of refractive error is
> not a function of the chart used. *Best corrected acuity measurement
> might be slightly more precise, but is of little practical benefit.
> Some optometrists or ophthalmologists mihgt have a Landolt C, few will
> have a Bailey Lovie chart, so even if you ask, they are unlikely to be
> able to do it. *Researchers and low vision specialists are more likely
> to have a Bailey Lovie chart.
> Judy

#10 05-04-2008, 07:18 PM

On May 2, 1:53*pm, douglas <Protoman2...[at]gmail.com> wrote:

- quote -

> > > Why don't ophthalmologists and optometrists use the Landolt C chart,
> > > instead of the Snellen chart? It's harder to cheat w/ the Landolt C.
> > Still, what if I ask my optometrist and ophthalmologist to test me w/
> the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> precise results?

More accurate what? Accuracy of determination of refractive error is
not a function of the chart used. Best corrected acuity measurement
might be slightly more precise, but is of little practical benefit.

Some optometrists or ophthalmologists mihgt have a Landolt C, few will
have a Bailey Lovie chart, so even if you ask, they are unlikely to be
able to do it. Researchers and low vision specialists are more likely
to have a Bailey Lovie chart.

Judy

#9 05-03-2008, 06:16 PM

On May 3, 5:49*am, Zetsu <absolutelyinvinci...[at]hotmail.com> wrote:
- quote -

> On 3 May, 10:03, douglas <Protoman2...[at]gmail.com> wrote:
> > On May 2, 2:30 pm, "Mike Tyner" <mty...[at]mindspring.com> wrote:
> > > "douglas" <Protoman2...[at]gmail.com> wrote
> > > > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > > > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > > > precise results?
> > > Perhaps, but that degree of precision is only useful in certain
> > > circumstances and it requires a new set of rules, compared to "let me hear
> > > you guess at the letters on this line."
> > > Landolt C is pretty widely used and your doctor may be happy to test your
> > > acuity that way.
> > > There's a children's version called "broken wheel".
> > > -MT
> > What about Bailey-Lovie? Think he'd be happy about that?
> Well, it's his job after all to examine and test people's vision. So
> being specialized in that field, I don't see him having any difficulty
> testing you with different acuity charts if you requested it. But
> also, you could print your own charts and test yourself! Because it's
> more fun that way! Or get a family member to test you or whatever.- Hide quoted text -
> - Show quoted text -

That would be fun! "Test your acuity!!! $5 to test your acuity!!!!"

#8 05-03-2008, 12:49 PM

On 3 May, 10:03, douglas <Protoman2...[at]gmail.com> wrote:
- quote -

> On May 2, 2:30 pm, "Mike Tyner" <mty...[at]mindspring.com> wrote:
> > "douglas" <Protoman2...[at]gmail.com> wrote
> > > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > > precise results?
> > Perhaps, but that degree of precision is only useful in certain
> > circumstances and it requires a new set of rules, compared to "let me hear
> > you guess at the letters on this line."
> > Landolt C is pretty widely used and your doctor may be happy to test your
> > acuity that way.
> > There's a children's version called "broken wheel".
> > -MT
> What about Bailey-Lovie? Think he'd be happy about that?

Well, it's his job after all to examine and test people's vision. So
being specialized in that field, I don't see him having any difficulty
testing you with different acuity charts if you requested it. But
also, you could print your own charts and test yourself! Because it's
more fun that way! Or get a family member to test you or whatever.

#7 05-03-2008, 09:03 AM

On May 2, 2:30*pm, "Mike Tyner" <mty...[at]mindspring.com> wrote:
- quote -

> "douglas" <Protoman2...[at]gmail.com> wrote
> > Still, what if I ask my optometrist and ophthalmologist to test me w/
> > the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> > precise results?
> Perhaps, but that degree of precision is only useful in certain
> circumstances and it requires a new set of rules, compared to "let me hear
> you guess at the letters on this line."
> Landolt C is pretty widely used and your doctor may be happy to test your
> acuity that way.
> There's a children's version called "broken wheel".
> -MT

What about Bailey-Lovie? Think he'd be happy about that?

#6 05-02-2008, 09:30 PM

"douglas" <Protoman2050[at]gmail.com> wrote

- quote -

> Still, what if I ask my optometrist and ophthalmologist to test me w/
> the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> precise results?

Perhaps, but that degree of precision is only useful in certain
circumstances and it requires a new set of rules, compared to "let me hear
you guess at the letters on this line."

Landolt C is pretty widely used and your doctor may be happy to test your
acuity that way.

There's a children's version called "broken wheel".

-MT

#5 05-02-2008, 09:16 PM

douglas schreef:
- quote -

> Why don't ophthalmologists and optometrists use the Landolt C chart,
> instead of the Snellen chart? It's harder to cheat w/ the Landolt C.

The first part is a wrong assumption.
It's a nice test when having a analfabetic in the chair.
Also handy when the examiner and the client don't speak the same
language or speaking is a problem.

For the second part, it's only more difficult to guess, cheating is not
the issue.

Jan (normally Dutch spoken)

#4 05-02-2008, 06:08 PM

douglas <Protoman2050[at]gmail.com> wrote in news:d33d3a33-32f9-4386-90a8-
6bed5569050e[at]c19g2000prf.googlegroups.com:

- quote -

> On May 2, 6:21*am, Scott Seidman <namdiestt...[at]mindspring.com> wrote:
> > douglas <Protoman2...[at]gmail.com> wrote in news:59daca38-01bb-45ca-8341-
> > 0131a3261...[at]h1g2000prh.googlegroups.com:
> > > > Why don't ophthalmologists and optometrists use the Landolt C chart,
> > > instead of the Snellen chart? It's harder to cheat w/ the Landolt C.
> > > They can get what they need from the Snellen, and its easy to use.
> > > For all serious (i.e., scientific) assessments, though, a Vernier acuity
> > task like the Landolt C really is the way to go.
> > --
> > Scott
> > Reverse name to reply
> Still, what if I ask my optometrist and ophthalmologist to test me w/
> the Landolt C or Bailey-Lovie chart? Will it give more accurate or
> precise results?

You don't need more accuracy to get the right correction. Vernier acuity
tests allow for better comparisions between studies and rule out any
cognitive influences on the tests.

--
Scott
Reverse name to reply

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