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Thread: Round Poly Transitions V Bifocal

  1. #1
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    Confused Round Poly Transitions V Bifocal

    I was going to see if anyone could help explain this to me:



    VisionMonday/May 16, 2005:



    "Three Rivers Optical, a major independent wholesale lab bases here (Pittsburg), has developed a new bifocal lens with a unique combination of features. The lens, available exclusively from Three Rivers, joins a round-segmented design in polycarbonate with the latest photochromic technology from Transitions Optical, Transitions V with ESP. Three Rivers is marketing the lens under the brand name "TR O SEG."



    later the article says:



    "Steve Seibert said round seg bifocals offer several advantages over flat-top bifocal designs, such as a thinner, less noticeable ledge and not as much image jump."



    ____________________________________________________________ ______



    I was looking for someone to help explain how this round bifocal is different from the previous versions of round bifocals currently available. It has been my understanding that round bifocals have nearly 3 x more image jump than Flat Top Bifocals.



    Example: Round 22 Plano +2.00 Add

    Prism = F x dec (mm)/10

    Prism = 2.00 x 11/10

    Prism = 2.2 base down



    Flat Top 22 Plano +2.00 Add

    Prism = F x dec (mm)/10

    Prism = 2.00 x 4/10

    Prism = 0.8 base down



    So I guess I am trying to figure out if Three Rivers reinvented the round bifocal or if perhaps a refresher course in Image Jump is needed.



    Adam

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    Bad address email on file Rich R's Avatar
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    Hello Adam, I believe they are referring to image jump when patient is looking at the top of the seg, not the center, so when going from distance to near it's not as abrupt of a change.

    I don't see much round bifocals anymore, so I don't know if there will be a demand for it in newer materials.
    Rich R

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    Think of a flat top as a prism, the ledge is going to create a base up prism, a round seg, where the thickness is in the center is going to create a base down affect thus you have a larger image jump in a flat top. Much like a jack in the box.

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    In the 70's when I was an apprentice, I was taught to put Hyperopes in Round segs and Myopes in Flat Tops. The reason was Image Jump. Later when Flat Tops were improved and became one piece of material, The thinking changed to Flat Tops for everyone. I'm sure the idea of less inventory for the Lab may have helped this thinking.
    John Zimmerman
    Sales Manager
    Tri-City Optical Laboratory

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    What's up? drk's Avatar
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    Thought I'd post on this:

    Just got my first TR- (ansitions) O- (round) SEG from Three Rivers Optical. Used it in place of a progressive for a young man with accommodative problems.

    It's invisible, to be sure. Transitions V technology. Polycarbonate. Larger zones than a progressive, especially distance zone compared to a short-corridor. What more can you want? (Other than a better name for the lens!)

    Looks like my lens of choice for kids with multifocals.

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    Banned Jim Stone's Avatar
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    Is there a round seg poly transition available? I have not heard of one (other than this one). If I am correct on that, Id say they are going after the ST28 poly transition market for dill rimless. See they haven't figured out how to make a st poly transition yet. Three Rivers was a fine lab when Bill was there. I don't know where his sons will wind up taking it.

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    Quote Originally Posted by drk
    Thought I'd post on this:

    Just got my first TR- (ansitions) O- (round) SEG from Three Rivers Optical. Used it in place of a progressive for a young man with accommodative problems.

    It's invisible, to be sure. Transitions V technology. Polycarbonate. Larger zones than a progressive, especially distance zone compared to a short-corridor. What more can you want? (Other than a better name for the lens!)

    Looks like my lens of choice for kids with multifocals.
    DRK,

    Do you recall if the lens is also available in brown or is it gray only? Thanks.

    Matt

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    Quote Originally Posted by Jim Stone
    See they haven't figured out how to make a st poly transition yet.
    You're right, there isn't a "Transitions" poly ST being made. But there is an ST photochromic poly available. It is made by Vision-Ease, called LifeRx D28, and is available through a select network of laboratories. Unlike other photochromics, the chemicals are not in the coating, enabling them to produce a flat-top.

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    Quote Originally Posted by OIC
    You're right, there isn't a "Transitions" poly ST being made. But there is an ST photochromic poly available. It is made by Vision-Ease, called LifeRx D28, and is available through a select network of laboratories. Unlike other photochromics, the chemicals are not in the coating, enabling them to produce a flat-top.
    There is however a "Transitions" Trilogy (Trivex) ST being made.

    Adam

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    Blue Jumper Round or Flat....................

    Quote Originally Posted by ken@foothills
    Think of a flat top as a prism, the ledge is going to create a base up prism, a round seg, where the thickness is in the center is going to create a base down affect thus you have a larger image jump in a flat top. Much like a jack in the box.
    You are pretty close.................On a FT the optical center of the segment is just about on the dividing line and if you would surface the distance with the center on the line you would have just about a zero image jump..............

    Whyle on the old Kryptok style bifocal (round seg.) the optical center of the segment is smack in the center, therefore you would get a massive image jump. However by the millions of people who used to wear them in the old days it did not seem to bother them too much.

    How about getting the Master (Meister) judge into this matter and come up with all the formulas I have forgotten years ago.

  11. #11
    Master OptiBoarder Darryl Meister's Avatar
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    Quote Originally Posted by Chris
    How about getting the Master (Meister) judge into this matter and come up with all the formulas I have forgotten years ago.
    Adam was actually right in the first place; you get more image jump in a round seg bifocal, since image jump is the prism created by the distance from the segment center to the ledge. This is why Executive-style bifocals, which have their segment center on the ledge, produce zero image jump, while an Ultex produced the most image jump.

    What John is referring to is object displacement at near, and is related to a slightly different effect from image jump. This is simply a technique that minimizes the base up or base down prism created by the distance portion at near by using prism in the opposite direction in the bifocal segment.

    That said, the round segments produced by Three Rivers are probably coming off of a free-form generator. These machines do not produce well-defined segment boundaries, so the edge of the segment has probably been smoothed into the distance portion slightly, creating a rapid (as opposed to instantaneous) transition into the prism, not entirely unlike the effect produced by a "blended" bifocal. Though I would have to see one to say for certain.
    Darryl J. Meister, ABOM

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    Darryl is right

    Quote Originally Posted by
    That said, the round segments produced by Three Rivers are probably coming off of a free-form generator. These machines do not produce well-defined segment boundaries, so the edge of the segment has probably been smoothed into the distance portion slightly, creating a [i
    rapid[/i] (as opposed to instantaneous) transition into the prism, not entirely unlike the effect produced by a "blended" bifocal. Though I would have to see one to say for certain.
    According to the Three Rivers rep the free form generator they got to make the Shamir Autograph was not being utilized (this is not a cheap piece of equipment to be sitting around collecting dust) so one of the guys in their lab decided to get a transitions blank and make a round seg in it.

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