Progressive Lens Identifier

I notice that the marking template for every progressive listed in the identifier has 15 mm from the fitting cross to the top of the near power circle, 20 mm to the bottom of the circle, about 18 to the middle, including short-corridor progressives.

Is this similarity significant? Aren't the diagrams provided by each manufacturer, or does the publication set the criteria for where to read the near power and distance power?

I would assume that the position of the near power circle would vary, since corridor length, whatever the definition, would vary from lens to lens.

Any insight on this? I posted this on the general discussion forum, but got no help. Your input is appreciated.

I actually tried to respond to your post yesterday - if you're referring to the one about seg "drops" - but our firewall got in the way, as it occasionally does; my message was lost, and I didn't have time to type it over.

The near power checking circle (the Near Reference Point) on a PAL is just that - it's not necessarily the point through which the patient will be gazing at near, which will almost certainly be higher. The NRP circle (like the DRP) is positioned at a point at which the least ambiguous power readings can be obtained.

I haven't gone through this exercise lately, but last time I looked, most NRP's were around 14mm below, and 2.5mm in, from their corresponding PRP's.

Let me try on this one. I was told about a year ago that one thing with all progressive lenses is constant. The distance between the fitting cross and the top of the circle is constant. So as you mentioned 15mm. The reason for this is there is only one press in the world that makes the imprint and it is in Israel. So whether you use the Super No Line or the Rodenstock XS the distance between the fitting cross and the reading area is 15mm. However corridor length and other variables are what the lens manufacturers use to give us a wider this and a deeper that.

I would like it if someone could please elaborate on what I said, because I only heard it once and I would like someone to clear it up further.

Quote:

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Originally Posted by For-Life

Let me try on this one. I was told about a year ago that one thing with all progressive lenses is constant. The distance between the fitting cross and the top of the circle is constant.

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Actually, the only established standard of which I'm aware is the separation between the engravings. Thats part of an ISO standard. I can't recall offhand either the ID of the standard or the value itself.

I would not expect the location of the Distance Reference Point (the power-checking circle on a PAL) and the Layout Reference Point (the fitting cross on a PAL) to be constant; I would expect it to vary with the design of the lens.

Quote:

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Originally Posted by drk

I notice that the marking template for every progressive listed in the identifier has 15 mm from the fitting cross to the top of the near power circle, 20 mm to the bottom of the circle, about 18 to the middle, including short-corridor progressives.
Is this similarity significant? Aren't the diagrams provided by each manufacturer, or does the publication set the criteria for where to read the near power and distance power?
I would assume that the position of the near power circle would vary, since corridor length, whatever the definition, would vary from lens to lens.
Any insight on this? I posted this on the general discussion forum, but got no help. Your input is appreciated.

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I don't think this is what drk was asking but I could be wrong. As I observe the latest Identifier, notice that the drawings are not to scale. In other words, the MRP of Zeiss is the same as Varilux, and the same as Seiko. Three examples of differnt lenses w/ respect to the fitting cross height above the 180. I suppose it follows that any other area you would want to measure is also not to scale, and hence the identifier should not be used as a marking template.

Is this helpful, or am I over simplifying the question? It is kind of silly that the pictures are portrayed as templates, when they are not.

:) I posted this on my tips on dispensing back last year, all progressive laser markings are 34 mm apart, which is nice, because you can draw a line over 17 mm, and then draw a line up 3 to 4 mm and come close to telling how far from the pupil you are.

MRBA is totally correct. It does seem that the progressive lens identifier holds itself out as a template to re-mark lenses for verification purposes, but upon further review, it's not. They clearly state that they are not drawn to scale, which I didn't take time to read. It's the same layout over and over, I might as well do what Saake says. I clearly got lead astray with my line of thinking, and I beg the "Board" for forgiveness for a time-waster.