Help converting prescription for readers please...
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AuntieM
Sep 21, 2008, 10:25:00 AM9/21/08
to GlassyEyes
Hi there!
Now that I have successfully ordered several (okay ... FIVE) pairs of
single vision glasses from Zenni, my husband is interested in
purchasing some durable readers in a titanium frame from them. He does
not wear glasses except for reading/close work. Recently he went to an
eye doctor for the first time in ages and received the following
prescription:
SPHERE CYLINDER AXIS ADD V/A
OD +025 +050 010 +250 20/20
OS +25 +025 005 +250 20/20
Am I correct that if filled as written these glasses would be bi-
focals? Since he doesn't wear glasses all the time (and
notwithstanding the prescription, he probably won't any time soon),
how do I order a pair of readers for him based on this prescription.
Is the ADD value of +250 the equivalent of a 2.50 magnification pair
of readers off the rack? I ask because he usually buys 1.50 readers
from the store.
Any help you all can give is MUCH appreciated. Thanks in advance.
Now that I have successfully ordered several (okay ... FIVE) pairs of
single vision glasses from Zenni, my husband is interested in
purchasing some durable readers in a titanium frame from them. He does
not wear glasses except for reading/close work. Recently he went to an
eye doctor for the first time in ages and received the following
prescription:
SPHERE CYLINDER AXIS ADD V/A
OD +025 +050 010 +250 20/20
OS +25 +025 005 +250 20/20
Am I correct that if filled as written these glasses would be bi-
focals? Since he doesn't wear glasses all the time (and
notwithstanding the prescription, he probably won't any time soon),
how do I order a pair of readers for him based on this prescription.
Is the ADD value of +250 the equivalent of a 2.50 magnification pair
of readers off the rack? I ask because he usually buys 1.50 readers
from the store.
Any help you all can give is MUCH appreciated. Thanks in advance.
Chuck Knight
Sep 21, 2008, 11:10:49 AM9/21/08
to AuntieM, GlassyEyes
His reading prescription is simple. It's calculated as SPH + ADD. In his case that's (+0.25) + (+2.50) = (+2.75).
He has astigmatism (CYL and AXIS), too, so his readers will be a bit more complicated than the average drug store pair. Should work better, too!
You said he usually wears +1.50? These will be quite a bit stronger.
-- Chuck Knight
P.S. Be sure to include an accurate PD reading!!!
He has astigmatism (CYL and AXIS), too, so his readers will be a bit more complicated than the average drug store pair. Should work better, too!
You said he usually wears +1.50? These will be quite a bit stronger.
-- Chuck Knight
P.S. Be sure to include an accurate PD reading!!!
onlineIDoc
Sep 21, 2008, 1:22:17 PM9/21/08
to GlassyEyes
NV rx:
+3.25 -.50 X 100
+2.75 -.25 x 95
transcribed to (-)cyl form as more popular (and technically correct)
On Sep 21, 11:10 am, "Chuck Knight" <chuckkni...@gmail.com> wrote:
> His reading prescription is simple. It's calculated as SPH + ADD. In his
> case that's (+0.25) + (+2.50) = (+2.75).
>
> He has astigmatism (CYL and AXIS), too, so his readers will be a bit more
> complicated than the average drug store pair. Should work better, too!
>
> You said he usually wears +1.50? These will be quite a bit stronger.
>
> -- Chuck Knight
>
> P.S. Be sure to include an accurate PD reading!!!
>
+3.25 -.50 X 100
+2.75 -.25 x 95
transcribed to (-)cyl form as more popular (and technically correct)
On Sep 21, 11:10 am, "Chuck Knight" <chuckkni...@gmail.com> wrote:
> His reading prescription is simple. It's calculated as SPH + ADD. In his
> case that's (+0.25) + (+2.50) = (+2.75).
>
> He has astigmatism (CYL and AXIS), too, so his readers will be a bit more
> complicated than the average drug store pair. Should work better, too!
>
> You said he usually wears +1.50? These will be quite a bit stronger.
>
> -- Chuck Knight
>
> P.S. Be sure to include an accurate PD reading!!!
>
Ev
Sep 22, 2008, 12:36:30 PM9/22/08
to GlassyEyes
As a bystander, I'm confused - why is Chuck's interpretation different
than online Doc's?
Am I missing something here?
than online Doc's?
Am I missing something here?
Chuck Knight
Sep 22, 2008, 1:18:47 PM9/22/08
to Ev, GlassyEyes
Frankly, I'm confused too. I've always been told that the combined total of the sphere and the add equals the reading prescription.
But, if my results differ from those of an eye doctor I always defer to the expert.
-- Chuck Knight
But, if my results differ from those of an eye doctor I always defer to the expert.
-- Chuck Knight
onlineIDoc
Sep 22, 2008, 4:01:39 PM9/22/08
to GlassyEyes
Sorry for the confusion. I just wanted to write the rx in the common
readable form so that his on line site would be more l;ikely.
Yes Chuck, you add the add to the sph which gives you
+3.25 -.50 X 100
+2.75 -.25 x 95
+2.75 +.50 x 10
+2.50 +.25 X 5
this is written in plus cyl form, note the plus sign on the cyl
cloumn. This is used mainly by older ophthamologists. Most now write
in minus sign form, first of all because its the way the glasses are
made. They can be converted vy transposition and are equilalent.
If in plus cyl you
1. Add the cyl to the sph, dont forget minus and plus math
2. change the cyl sign to -
3. leave the cyl number alone
4. move the axis 90 degrees.
wasnt trying to make it so complicated, buyt my fear was as a newbie
he might punch his cyls into a form which assumes minus, many do. I
supose the sites do check for this. But there you go Chuck, another
little trick. I heard you're quite a brilliant guy
Sincerely
Michael Katz OD
> > > > > Any help you all can give is MUCH appreciated. Thanks in advance.- Hide quoted text -
>
> - Show quoted text -
readable form so that his on line site would be more l;ikely.
Yes Chuck, you add the add to the sph which gives you
+3.25 -.50 X 100
+2.75 -.25 x 95
+2.50 +.25 X 5
this is written in plus cyl form, note the plus sign on the cyl
cloumn. This is used mainly by older ophthamologists. Most now write
in minus sign form, first of all because its the way the glasses are
made. They can be converted vy transposition and are equilalent.
If in plus cyl you
1. Add the cyl to the sph, dont forget minus and plus math
2. change the cyl sign to -
3. leave the cyl number alone
4. move the axis 90 degrees.
wasnt trying to make it so complicated, buyt my fear was as a newbie
he might punch his cyls into a form which assumes minus, many do. I
supose the sites do check for this. But there you go Chuck, another
little trick. I heard you're quite a brilliant guy
Sincerely
Michael Katz OD
>
> - Show quoted text -
Bjalf
Sep 22, 2008, 2:57:45 PM9/22/08
to GlassyEyes
On Sep 22, 7:18 pm, "Chuck Knight" <chuckkni...@gmail.com> wrote:
> Frankly, I'm confused too. I've always been told that the combined total of
> the sphere and the add equals the reading prescription.
He also changed the + cylinder values to - cylinder values. When you
> Frankly, I'm confused too. I've always been told that the combined total of
> the sphere and the add equals the reading prescription.
do that, you apparently have to adjust the sphere values in addition
to changing the axis values.
Still, the numbers don't really add up. How did this:
+2.75 +0.50 x 010
+2.75 +0.25 x 005
turn into this?
+3.25 -0.50 x 100
+2.75 -0.25 x 95
Chuck Knight
Sep 22, 2008, 6:01:51 PM9/22/08
to GlassyEyes
Let me take a stab at it...see if I understand it.
The cylinder part of a prescription has an effect on the total magnification...at the optical center, through the lens, with a prescription of +2.75 x +0.50, the total magnification would be +3.25. The cylinder effect tapers off towards the edges.
To achieve the same effect (stronger in the middle, weaker on the edges) but using a negative cylinder, you would have to start with a stronger spherical prescription, i.e. +3.25, and then *subtract* the cylinder of -0.5, to end up with the magnification on the edges being the original +2.75. And, for it to have the opposite effect, the axis would have to be turned at 90 degrees from the original prescription.
This actually makes sense to me. Not sure if that should concern me, or not! :-)
-- Chuck Knight
The cylinder part of a prescription has an effect on the total magnification...at the optical center, through the lens, with a prescription of +2.75 x +0.50, the total magnification would be +3.25. The cylinder effect tapers off towards the edges.
To achieve the same effect (stronger in the middle, weaker on the edges) but using a negative cylinder, you would have to start with a stronger spherical prescription, i.e. +3.25, and then *subtract* the cylinder of -0.5, to end up with the magnification on the edges being the original +2.75. And, for it to have the opposite effect, the axis would have to be turned at 90 degrees from the original prescription.
This actually makes sense to me. Not sure if that should concern me, or not! :-)
-- Chuck Knight
Bjalf
Sep 23, 2008, 9:43:57 AM9/23/08
to GlassyEyes
On Sep 22, 10:01 pm, onlineIDoc <mkat...@gmail.com> wrote:
> Sorry for the confusion. I just wanted to write the rx in the common
> readable form so that his on line site would be more l;ikely.
>
> Yes Chuck, you add the add to the sph which gives you
>
> +3.25 -.50 X 100
> +2.75 -.25 x 95
>
> +2.75 +.50 x 10
> +2.50 +.25 X 5
>
This is starting to make sense to me, except that I thought that the
> Sorry for the confusion. I just wanted to write the rx in the common
> readable form so that his on line site would be more l;ikely.
>
> Yes Chuck, you add the add to the sph which gives you
>
> +3.25 -.50 X 100
> +2.75 -.25 x 95
>
> +2.75 +.50 x 10
> +2.50 +.25 X 5
>
original prescription was
+2.75 +0.50 x 010
+2.75 +0.25 x 005
and not
+2.75 +0.25 x 005
+2.75 +0.50 x 010
+2.50 +0.25 x 005
ehb
Sep 23, 2008, 10:16:17 AM9/23/08
to GlassyEyes
OnlineDoc,
Correct me if I am wrong but didn't the switch from plus to minus
cylinder occur at about the same time that the switch from glass
lenses (which were usually custom ground so the cylinder had to be
added to the sphere correction) to plastic lenses (which were
premolded with base prescription built in and then finished on the
lathe which cut out or subtracted the cylinder correction)? I can
remember some of my old plus cylinder precriptions from about 30 or so
years ago when I wore case hardened glass lenses that and my minus
sphere was about a diopter or two more than it is now (which coincides
with the strength of my cylinder correction).
Correct me if I am wrong but didn't the switch from plus to minus
cylinder occur at about the same time that the switch from glass
lenses (which were usually custom ground so the cylinder had to be
added to the sphere correction) to plastic lenses (which were
premolded with base prescription built in and then finished on the
lathe which cut out or subtracted the cylinder correction)? I can
remember some of my old plus cylinder precriptions from about 30 or so
years ago when I wore case hardened glass lenses that and my minus
sphere was about a diopter or two more than it is now (which coincides
with the strength of my cylinder correction).
onlineIDoc
Sep 24, 2008, 10:53:00 PM9/24/08
to GlassyEyes
very good, that was history when i started this thing over 30 years
ago. Yes, many reasons, arguements, cost of production has gone on
since then. But in almost all cases it ends up minus cyl today ,even
glass.
Once in a lifetime you get some crazy rx that has to be ground on the
front, but they usually see specialists as this usually accompanies
pathology, usually of the cornea.
But kudos
Mike Katz
ago. Yes, many reasons, arguements, cost of production has gone on
since then. But in almost all cases it ends up minus cyl today ,even
glass.
Once in a lifetime you get some crazy rx that has to be ground on the
front, but they usually see specialists as this usually accompanies
pathology, usually of the cornea.
But kudos
Mike Katz
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