Thanks everyone for helping me about 4 weeks ago with my questions re
'progressive' lenses.

I am now ready for bifocals. The progressives are wonderful for garage
sales and the supermarket. I no longer have to get on my knees to read
phono album and book titles. They are useless for all other purposes.

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use +1.5
reading glasses for the screen, and switch back and forth to +2.5 reading
glasses for reading. If I want bifocals that do the same thing (obviate the
switching) what numbers do I use? Where do I plug in the +1.5 value?

Any and all help greatly appreciated.

Ivan Vegvary

Ivan Vegvary writes:

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use
+1.5 reading glasses for the screen, and switch back and forth to +2.5
reading glasses for reading. If I want bifocals that do the same
thing (obviate the switching) what numbers do I use? Where do I plug
in the +1.5 value?

Change both adds to +1.5, instead of +2.5.

Why: The spherical/cylindrical lens should correct your vision for
focusing at infinity. The additional positive refraction (the "add") is
specified in diopters, which is the inverse of the focal length in
meters. If you hold a lens of power d in diopters in front of your
infinity-focused eyes, you will then focus instead at 1/d meters. So a
+1.5 add will focus at about 1/1.5 = 0.67 meters, or about 2 feet, which
for most people is a suitable computer screen reading distance. Your
2.5 add let you read a book 1/2.5 = 0.4 meters, or about 16 inches, from
your face, suitable for books.

So whatever distance you want to sit from the screen, in meters, invert
that and specify it as the "add" number.

Rather than bifocals for the computer, you might consider single-vision
lenses so you're not tipping your head about to read the screen. For
that you would specify no add, and instead add 1.5 to the spherical Rx
numbers, that is, 2.25 and 2.50 instead of 0.75 and 1.00.

"Richard J Kinch" wrote in message
.. .
Ivan Vegvary writes:

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use
+1.5 reading glasses for the screen, and switch back and forth to +2.5
reading glasses for reading. If I want bifocals that do the same
thing (obviate the switching) what numbers do I use? Where do I plug
in the +1.5 value?

Change both adds to +1.5, instead of +2.5.

Why: The spherical/cylindrical lens should correct your vision for
focusing at infinity. The additional positive refraction (the "add") is
specified in diopters, which is the inverse of the focal length in
meters. If you hold a lens of power d in diopters in front of your
infinity-focused eyes, you will then focus instead at 1/d meters. So a
+1.5 add will focus at about 1/1.5 = 0.67 meters, or about 2 feet, which
for most people is a suitable computer screen reading distance. Your
2.5 add let you read a book 1/2.5 = 0.4 meters, or about 16 inches, from
your face, suitable for books.

So whatever distance you want to sit from the screen, in meters, invert
that and specify it as the "add" number.

Rather than bifocals for the computer, you might consider single-vision
lenses so you're not tipping your head about to read the screen. For
that you would specify no add, and instead add 1.5 to the spherical Rx
numbers, that is, 2.25 and 2.50 instead of 0.75 and 1.00.

Richard, thank you for your insightful reply. However, I want to be sure
that we are talking about the same thing.

I often have to do computer work (1.5 reading glasses work fine) while at
the same time I am making entries from a hand held manual or drawing. For
that I have to take off my computer glasses (1.5) put on my reading glasses
(2.5) read a sentence or dimension, replace my computer glasses and make a
keyboard entry. I was hoping to find a bifocal that will allow me to do
both with one set of glasses. Please advise.

Thank you
Ivan Vegvary

"Ivan Vegvary" wrote in message
...

"Richard J Kinch" wrote in message
.. .
Ivan Vegvary writes:

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use
+1.5 reading glasses for the screen, and switch back and forth to +2.5
reading glasses for reading. If I want bifocals that do the same
thing (obviate the switching) what numbers do I use? Where do I plug
in the +1.5 value?

Change both adds to +1.5, instead of +2.5.

Why: The spherical/cylindrical lens should correct your vision for
focusing at infinity. The additional positive refraction (the "add") is
specified in diopters, which is the inverse of the focal length in
meters. If you hold a lens of power d in diopters in front of your
infinity-focused eyes, you will then focus instead at 1/d meters. So a
+1.5 add will focus at about 1/1.5 = 0.67 meters, or about 2 feet, which
for most people is a suitable computer screen reading distance. Your
2.5 add let you read a book 1/2.5 = 0.4 meters, or about 16 inches, from
your face, suitable for books.

So whatever distance you want to sit from the screen, in meters, invert
that and specify it as the "add" number.

Rather than bifocals for the computer, you might consider single-vision
lenses so you're not tipping your head about to read the screen. For
that you would specify no add, and instead add 1.5 to the spherical Rx
numbers, that is, 2.25 and 2.50 instead of 0.75 and 1.00.

Richard, thank you for your insightful reply. However, I want to be sure
that we are talking about the same thing.

I often have to do computer work (1.5 reading glasses work fine) while at
the same time I am making entries from a hand held manual or drawing. For
that I have to take off my computer glasses (1.5) put on my reading
glasses (2.5) read a sentence or dimension, replace my computer glasses
and make a keyboard entry. I was hoping to find a bifocal that will allow
me to do both with one set of glasses. Please advise.

Thank you
Ivan Vegvary

OK, add 1.5 to the main prescription and then make the bifocal only +1. YMMV
but I have the same issue, I'd go +1 on the main prescription and have +1.5
on the bifocals. Means the computer has to be 6 or 8 inches farther away

OD SP +2.25, Cyl -0.75, Axis 098, Read Add +1.0
OS SP +2.50, Cyl -0.50, Axis 110, Read Add +1.0
for your request.


Karl

In article ,
"Ivan Vegvary" wrote:

"Richard J Kinch" wrote in message
.. .
Ivan Vegvary writes:

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use
+1.5 reading glasses for the screen, and switch back and forth to +2.5
reading glasses for reading. If I want bifocals that do the same
thing (obviate the switching) what numbers do I use? Where do I plug
in the +1.5 value?

Change both adds to +1.5, instead of +2.5.

Why: The spherical/cylindrical lens should correct your vision for
focusing at infinity. The additional positive refraction (the "add") is
specified in diopters, which is the inverse of the focal length in
meters. If you hold a lens of power d in diopters in front of your
infinity-focused eyes, you will then focus instead at 1/d meters. So a
+1.5 add will focus at about 1/1.5 = 0.67 meters, or about 2 feet, which
for most people is a suitable computer screen reading distance. Your
2.5 add let you read a book 1/2.5 = 0.4 meters, or about 16 inches, from
your face, suitable for books.

So whatever distance you want to sit from the screen, in meters, invert
that and specify it as the "add" number.

Rather than bifocals for the computer, you might consider single-vision
lenses so you're not tipping your head about to read the screen. For
that you would specify no add, and instead add 1.5 to the spherical Rx
numbers, that is, 2.25 and 2.50 instead of 0.75 and 1.00.

Richard, thank you for your insightful reply. However, I want to be sure
that we are talking about the same thing.

I often have to do computer work (1.5 reading glasses work fine) while at
the same time I am making entries from a hand held manual or drawing. For
that I have to take off my computer glasses (1.5) put on my reading glasses
(2.5) read a sentence or dimension, replace my computer glasses and make a
keyboard entry. I was hoping to find a bifocal that will allow me to do
both with one set of glasses. Please advise.

It's a reasonable combination to have computer glasses above and reading
glasses below in the same pair of bifocals.

Joe Gwinn

Ivan Vegvary writes:

I was hoping to find a bifocal that will allow me to do
both with one set of glasses. Please advise.

Like another follow-up post says, add 1.5D to the spherical Rx, and specify
the bifocal adds to be 1.0D. Then you'll focus 2 feet straight ahead, and
16 inches down through the bifocals.

Richard J Kinch wrote:
Ivan Vegvary writes:

I want to order some bifocals, and obviously I will use the same
prescriptions.
OD SP +0.75, Cyl -0.75, Axis 098, Read Add +2.5
OS SP +1.00, Cyl -0.50, Axis 110, Read Add +2.5

However, I would also like to order a pair for the computer. I use
+1.5 reading glasses for the screen, and switch back and forth to +2.5
reading glasses for reading. If I want bifocals that do the same
thing (obviate the switching) what numbers do I use? Where do I plug
in the +1.5 value?

Change both adds to +1.5, instead of +2.5.

Why: The spherical/cylindrical lens should correct your vision for
focusing at infinity. The additional positive refraction (the "add") is
specified in diopters, which is the inverse of the focal length in
meters. If you hold a lens of power d in diopters in front of your
infinity-focused eyes, you will then focus instead at 1/d meters. So a
+1.5 add will focus at about 1/1.5 = 0.67 meters, or about 2 feet, which
for most people is a suitable computer screen reading distance. Your
2.5 add let you read a book 1/2.5 = 0.4 meters, or about 16 inches, from
your face, suitable for books.

So whatever distance you want to sit from the screen, in meters, invert
that and specify it as the "add" number.

Rather than bifocals for the computer, you might consider single-vision
lenses so you're not tipping your head about to read the screen. For
that you would specify no add, and instead add 1.5 to the spherical Rx
numbers, that is, 2.25 and 2.50 instead of 0.75 and 1.00.


I am currently looking at new glasses for the wife.
Her problem is that she can see fine without correction out to 20-24"
After that the world becomes a big blur.

What I tried to talk to the doc about was a pair of bifocals with
correction on top and none on the bottom, he looked at me like I was
nuts. I would think it was a more common thing than what he seemed to
think.

OD SP -2.75, Cyl -0.25, Axis 175
OS SP -2.75, Cyl -0.75, Axis 155

Someone have an idea? Other than a new wife....

--
Steve W.