What do the +/- numbers mean after acuity?

My optometrist told me my acuity measured as 20/40 +2, but I forgot
what his explanation of the extra integer was. What does it mean when
acuity has +/- numbers?

This depends on the OD who writes the "plus" or "minus" after you read
your Snellen for him.

If you incorrectly read on letter, he can record the fact that you did
not read the line perfectly ( 0 ).

More typically, it will be marked at 20/20, -2 indicating that you did
not read two characters correctly.

The best idea, is to simply ask the OD what he means when he writes +2
after your reading of the Snellen.

Second-opinion best,





On Dec 12, 3:47*am, douglas <protoman2...@gmail.com> wrote:
> My optometrist told me my acuity measured as 20/40 +2, but I forgot
> what his explanation of the extra integer was. What does it mean when
> acuity has +/- numbers?

On Dec 12, 7:47*am, "Mike Tyner" <mty...@mindspring.com> wrote:
> "Otis" <otisbr...@embarqmail.com> wrote
>
> > This depends on the OD who writes the "plus" or "minus" after
> > you read your Snellen for him.
> > If you incorrectly read on letter, he can record the fact that you
> > did not read the line perfectly ( 0 ).
>
> Your answers are WRONG because you have no education or experience in eye
> care. *There is nothing ambiguous about this marking system. It's your
> understanding that is lacking. Why are you answering questions in an area
> where you have no training or experience?
>
> Snellen acuity is defined as the smallest line at which you can guess at
> least half the letters correctly.
>
> > The best idea, is to simply ask the OD what he means when he
> > writes +2 after your reading of the Snellen.
>
> It means he read 2 letters off the NEXT line.
>
> Why don't you limit yourself to answering all the ENGINEERING questions that
> pop up here?

I love when he deletes the posts that even HE realizes are just
idiotic.

If only he realized how idiotic ALL of his posts are.....

On Dec 12, 6:47*am, "Mike Tyner" <mty...@mindspring.com> wrote:
> "Otis" <otisbr...@embarqmail.com> wrote
>
> > This depends on the OD who writes the "plus" or "minus" after
> > you read your Snellen for him.
> > If you incorrectly read on letter, he can record the fact that you
> > did not read the line perfectly ( 0 ).
>
> Your answers are WRONG because you have no education or experience in eye
> care. *There is nothing ambiguous about this marking system. It's your
> understanding that is lacking. Why are you answering questions in an area
> where you have no training or experience?
>
> Snellen acuity is defined as the smallest line at which you can guess at
> least half the letters correctly.
>
> > The best idea, is to simply ask the OD what he means when he
> > writes +2 after your reading of the Snellen.
>
> It means he read 2 letters off the NEXT line.
>
> Why don't you limit yourself to answering all the ENGINEERING questions that
> pop up here?

Does the fact that you need +/- numbers for a Snellen eye chart means
that maybe that chart is slightly confounding acuity with pattern
recognition, since some letters are more distinct than others? Why
don't the just use the HOTV chart, where the characters used in each
line don't change?

On Dec 12, 4:14*pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> "douglas" <protoman2...@gmail.com> wrote
>
> > Does the fact that you need +/- numbers for a Snellen eye chart means
> > that maybe that chart is slightly confounding acuity with pattern
> > recognition, since some letters are more distinct than others? Why
> > don't the just use the HOTV chart, where the characters used in each
> > line don't change?
>
> No no no... The only purpose for the +/- is to allow interpolated
> measurements. If the 20/20 line says H O T V, and you read "H O P W," then
> that's "20/20 -2."
>
> If each line has only four letters, then "20/20-2" would record the same
> thing as "20/25 +2".
>
> Character recognition does indeed add a layer of complexity, so Snellen
> acuity is too variable for greater precision than "20/25 plus a couple".
>
> If you want more precision, you switch to Landolt C, or vernier acuity
> tests.
>
> -MT

I hope I can convince the optometrist I'll be seeing to evaluate me
for a Visian ICL to use a Landolt C chart to determine my ICL
prescription (though I think that'll be taken care of by the
aberrometer and the other devices). I definitely don't want to pay
$3500 for a slightly-off implant.

On Dec 12, 5:49*pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> "douglas" <protoman2...@gmail.com> wrote
>
> > I hope I can convince the optometrist I'll be seeing to evaluate me
> > for a Visian ICL to use a Landolt C chart to determine my ICL
> > prescription (though I think that'll be taken care of by the
> > aberrometer and the other devices). I definitely don't want to pay
> > $3500 for a slightly-off implant.
>
> The surgeon probably won't rely on an "outside" refraction, if he needs one
> at all.
>
> Regardless, notice that refraction and acuity do not measure the same thing.
>
> You can measure refraction precisely using only black dots or circles. The
> lens necessary to optimize the focus on a page of black dots would be the
> same lens necessary to focus "HOTV" or the "broken wheel" or even the big
> "E". Distance equates with diopters, and the content is irrelevant, for
> purposes of refraction.
>
> Small, high-contrast letters (or dots) are better for discriminating the
> clarity of one diopter value over another. *Round and regular letters are
> more reliable for measuring astigmatism.
>
> Other than that, it really doesn't matter what's _on_ the chart. Refraction
> depends on how blurry it is, not what the letters are.
>
> -MT, OD

Well, my OD and EyeMD are sending over my records to him, and my EyeMD
is a colleague of his from residency who he told me he respects him
highly. But's that for the purpose of asessing my general eye health;
he told me he'll be doing specialized tests as a part of the pre-op
exam.

Just wondering: Can a profoundly myopic (-12.5) patient with grade 2
ROP have cataract surgery safely, or is the risk of retinal detachment
too high. My eye surgeon told me in emails that replacing the natural
lens with an IOL would cause the vitreous to swell and put undue
traction on the retina, on top of the traction due to increased length
of the eyeball, plus the traction from the ROP.