What is the situation with TRI-focals?
When you say the same size I assume that means the reading portion of
the lens is present all the way across at the bottom.
> What is the situation with TRI-focals?
For tri-focal lenses, there are three sections in the lens for seeing at
three distances, distance (walking, driving), intermediate (computer
work) and near (reading). For executive trifocals right between the
distance Rx and the reading Rx is the relatively narrow band of lens for
vision at intermediate distance.
Hope that helps.
the first number is the depth of intermediate area and the second is the width
of the seg (both in MM)
7x25 7x28 8x35 10x35 12x35
ultex trifocal (looks like two half circles at the bottom of the frame
FT seg in the bottom of the and at the top 14mm seperating the two segs..your
eye sets in bewteen them (used by plumbers,elctricains etc. also by some
computer people (depends on your work conditions monitor, keyboard location)
available in ft28 version, rd bifocals top and bottom, and full field seg
(elines called a CRT trifocal)
Then you have the ED and FD trifocals...its an exectutive (Eline..bi-focal
clear across the lens) with a small seg ft 28 dropped into it ,
this is for a wide area in the intermediate so you don't have to move your
difference between the ED and FD is in the space or depth of the intermediate
area and the power of the intermediate area.
The ED is 8mm down and 50% of the reading seg . The FD is 6mm down to the
reading seg and intermediate is 60% of the near power
thats about all of the designs I ca think of right off the top of my head
but I can go dig if you need more choices....
OHH... as for the uses in the powers??..I always explain it as the bottom
reading seg is for 18 inches the intermediate brings that area of arms length
to around 6 to 8 feet into focus and then the distant is self explanatory :-)
hope this helped out some.. I'm sure someone will fill in a few I probably
missed in designs
When E line or F line (Executive, etc) are cut into a frame, the
distance and near portions are rarely the same size, but I am guessing
that you are referring to the line running the entire horizontal width
of the lens.
If you need trifocals, you can save yourself alot of problems with
weight, discomfort, and stability in a larger frame (not even
mentioning appearance,) by trying either an ED (gives you the
"executive style" intermediate with a smaller 25 to 28(FD) mm reading
seg, or one of the wide varieties of occupational segs such as the
Rodenstock C10x40. It gives a reading segment 40mm wide and 25mm deep
and an intermediate 10 mm deep and almost as wide (less than 2mm
smaller). THe 14x35mm seg lens gives a larger height in the
intermediate than the 10x40 with a minimal loss of width.
If you really must have a lens like that, they do still make trifocal
versions. Orcolite, American Optical, and X-Cel make a CRT E or F line
(same thing, silly trademark thing, Silor calls it's full line lens
"Diplomat", it's like a bad joke.) lens that has an intermediate
segment 14mm high. Most other "executive "style trifocals have an
intermediate half of that height. Blank sizes, materials, and power
ranges are limited due to unpopularity of the characteristics of the
I'm sure Jeff will fill in any blanks I left out! :)
> Then you have the ED and FD trifocals...its an exectutive (Eline..bi-focal
> clear across the lens) with a small seg ft 28 dropped into it ,
> this is for a wide area in the intermediate so you don't have to move your
> head alot)
> difference between the ED and FD is in the space or depth of the intermediate
> area and the power of the intermediate area.
> The ED is 8mm down and 50% of the reading seg . The FD is 6mm down to the
> reading seg and intermediate is 60% of the near power
I think the FD intermediate zone is about 13 mm high. I'm
sure it's not 6.
The exec tri has a 7 or 8 mm intermediate (7 for glass, 8
for plastic, maybe?)
I sure wish they made an exec trifocal with 10 and 14 mm
And while they're at it, I wish they'd chamfer that exec
line at the temporal edge...
I prefer to go by memory :-) but you had to make me go dig up the info
didn't ya!! LOL.. the seg line of the full field add , exec, diplomat or
wahtever anyone feels like calling it is only 6mm above the D seg.. beats me
why they went for such a narrow field there....the 13mm number you are thinking
about is some sub thought on the distance between segs in an occupational!!LOL
Which by the way you ever dispensed out an occupational that has the round
segs??,,,they look so weird and I thought the D segs were bad enough. I had to
do a pair the other day for someone and to beat all the OD decided that the
patient needed a slab ONTOP of wearing the uccupational...arrrgggghhh.. I did
it with great reluctence and knowing that if I ground base down in both eyes it
would have worked just as well (only a 1.5^ imbalance) and the guy put them on
and today he was back!!...HATED THEM...MEAN IT!! LOL Now we are redoing them
the way I wanted to do beging with... some OD's are stubborn as all get out
when it comes to asking about anything when it comes to the glasses side of it.
Oh well keeps me cranking out Dr' Redo's though:-)
Gotta scoot... got a forest fire knocking on my back door!!LOL
X-Cel's FD is 13mm between the intermediate line and the near line.
The 6mm is the inset of the near seg. Yes, Bill, I have the same
Opthalmic reference guides. It's in my lap as I type. The intermediate
step percentage is right on.
> I think the FD intermediate zone is about 13 mm high. I'm
> sure it's not 6.
6mm is the inset Jeff!
> The exec tri has a 7 or 8 mm intermediate (7 for glass, 8
> for plastic, maybe?)
> I sure wish they made an exec trifocal with 10 and 14 mm
THey do, it's called a CRT lens. AO, Vision-Ease, and X-Cell make
them. They all offer a 14mm intermediate height. Don't expect them to
be readily available as the market shrinks, it'll soon be 6 or 7 week
backorders from the manufacturer as the demand drops. This is typical
for both overly desired designs and nearly obsolete designs. Anyone
tried to order a PGX Philtex A lately?
> And while they're at it, I wish they'd chamfer that exec
> line at the temporal edge...
Good luck on that one. The design is rotten to begin with. The only
Exec style that I found to be designed relatively properly is the Sola
decentered version. It still ends up rotten when we have an
earthquake. We need an edger that can withstand seismic disturbances.
Yep, it's the CRT exec trifocal. It's as hideous as the worst optical
nightmares ever produced, but it has it's place. I just did a Z87 pair
two weeks ago. Yikes! The wearer will have the neck of an Olympian in
a month or two. He'll be able to pull dogsleds with the harness around
> Which by the way you ever dispensed out an occupational that has the round
> segs??,,,they look so weird and I thought the D segs were bad enough.
Yeah, I have. They were previous wearers. I also have a 5% number of
I had to
> do a pair the other day for someone and to beat all the OD decided that the
> patient needed a slab ONTOP of wearing the uccupational...arrrgggghhh..
Slab off on a RD seg? That is a redo from the start. I'd refuse such
an order and explained to the patient why. I'd even pull out a trial
set just to show what was prescribed. (I have a set of half frame
> it with great reluctence and knowing that if I ground base down in both eyes it
> would have worked just as well (only a 1.5^ imbalance) and the guy put them on
> and today he was back!!...HATED THEM...MEAN IT!! LOL Now we are redoing them
> the way I wanted to do beging with... some OD's are stubborn as all get out
> when it comes to asking about anything when it comes to the glasses side of it.
> Oh well keeps me cranking out Dr' Redo's though:-)
I'm still amazed that ODs can presribe things like that in your state.
In AK, we only need the Dx Rx and any NX Rx and fill them to the
patients' needs. ODs have too many other things to worry about.
There's no way they can keep track of all of the lens
designs/materials and frame options.
> Gotta scoot... got a forest fire knocking on my back door!!LOL
I've been watching the footage about the wildfires in FL. 8 of my
friends are Hot Shot members called from AK to help y'all. You have
the best of the best trying to beat mother nature at her own game.
Professionals are on hand. You'd be amazed at what they can pull off.
I just hope Canada can free up some of her A-26 fire bombers. They are
the hot rods of the slurry bombers. I remember seeing them suppress
the breach in a black spruce forest that nearly killed me and several
other members of the Meadow Lakes Volunteer Fire Service three years
ago during the Millers Reach fire. We were in an area that was rich in
black spruce protecting homes. Black spruce even when green are little
better than gasoline soaked sticks. Choppers couldn't pull us out, and
I was wishing to be back in my lab safe and sound. A flight of A-26
bombers from Canada repeatedly soaked the area with an unbelievable
accuracy. I witnessed a dump just 100 ft from me while I was calling
in the plane by cellular. It allowed our crew to to get out and reform
in a birch stand with a D7 cat ready to plow a break a half mile ahead
of the leading edge.
THe Yellow Shirts are the tamers of wildfires. Salutes and best wishes
to our Hot Shot crews of several states. They go where none of the
rest of us would ever want to be. THe bomber crews also deserve many
salutations. THey fly through the maelstrom of a wild fire to give the
ground crews a chance to survive.
The design is rotten to begin with.
Maybe the physical aspects are unlovely, but the optics are
nice ("no-jump") when the line is well-made (a clean break
with no prism).
Thanks for the info on the 14 mm sep CRT tri, I might just
try out a pair.
IMO all progressives look nice but are rotten optically
whenever viewing a comp. monitor or an serious close work.
My personal computer glasses are exec bi with +.75 over my
refractive error in the distance and a 1 add, which now
needs to go to 1.25. Sigh.
I'm using a set of 14x35mm trifocals at the moment. I keep then in a
case velcroed to the side of the monitor. I've yet to meet a
progressive I truly like to look through for computer use. I guess I'm
just too picky for my own good. LOL I'm somewhat happy with the
Percepta for general wear.
Specs31 wrote in message
>FT seg in the bottom of the and at the top 14mm seperating the two
>eye sets in bewteen them (used by plumbers,elctricains etc. also by some
>computer people (depends on your work conditions monitor, keyboard
>available in ft28 version, rd bifocals top and bottom, and full field seg
>(elines called a CRT trifocal)
"Occupational" Execs, or "Double Segs", are not at all the same as "CRT
trifocals", which have the same form as regular exec trifocals, but with a
taller intermediate zone - I can't remember offhand if it's 10mm or 14mm.
Ever see a double seg combo of flat-top and round seg? I have, but I can't
> Tri-focals are available in a variety of sizes both in width and depth as
>well as design....
>the first number is the depth of intermediate area
What in the world is a "depth of an area"? You mean the *height* of
the segment, I presume.
>I sure wish they made an exec trifocal with 10 and 14 mm
>And while they're at it, I wish they'd chamfer that exec
>line at the temporal edge...
Comes the electronickers with HD digital optometry and you can dial
whatever you want +/- 1 pixel. 10｢/doz lenses.
> I'm using a set of 14x35mm trifocals at the moment.
I guess what's kept me from trying that one for "serious"
computer work (>15 min) is that I don't have much need for a
distance correction in that situation, so having the entire
upper lens available for the monitor is comfy.