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IÂ’m doing a deep dive on progressives and all the lenses seem to say the same thing on their websites: improve vision, smoother transition, wider fields of view.
I really want a cheat sheet like: minus low add use ____, plus high add use ____, high cyl use ____ etc.
anybody have recommendations?
I think we're past that, Jake.
Choose: Shamir. Essilor. Hoya. Zeiss.
Then choose the middle of their lines and use it for everyone. They have it all figured out for you.
Into the abyss you go!
Post #11 in particular but as drk suggests it's all about the fit and imo Ryser's rule:
https://www.optiboard.com/forums/sho...o-complicated?
Other Hall of Fame forum threads follow more current digital's as well.
that’s was IMMENSELY helpful! Thank you!Quote:
Originally Posted by Uncle Fester
Viewing Zone Configuration
Unlike lined multifocals, the central viewing zones of a progressive lens are not well-defined. The size and utility of the viewing zone will vary depending upon both the wearer's tolerance to blur and the nature of the visual task. For instance, the blur produced by unwanted astigmatism in the periphery of a progressive lens may make certain critical viewing tasks—such as reading—difficult, though these regions may be perfectly acceptable for dynamic vision, which often requires only localizing and recognizing objects.Nevertheless, the lens designer can define the size and shape of the central viewing zones by establishing a limit on the amount of acceptable power error, including the maximum levels of unwanted astigmatism and mean power error. (For our purposes, the mean power errorrepresents the difference between the mean power produced by the lens design and the Add power actually required for a given reading distance.)For a given power error threshold, the size of the central viewing zones can be increased by pushing the unwanted astigmatism farther into the periphery. However, this trade-off results in a harder lens design with higher and more rapidly increasing levels of unwanted astigmatism. Because of this trade-off, lens designers must be careful not to increase the size of any particular central viewing zone any more than necessary.The size of each viewing zone should be judiciously managed in order to provide the best overall balance by maximizing the global utility of the lens design. Therefore, lens designers must choose the best balance between the size of the distance zone and the size of the near zone, so that both zones function comparably for the wearer. Of course, this will ultimately depend on the nature and frequency of the visual tasks performed by the wearer.http://opticampus.opti.vision/progre...es/Slide20.GIF
http://opticampus.opti.vision/popcourse.php?url=progressive_lenses/#configuration
I would recommend that everyone observe the cylinder maps of various PALs to see the similarity in shapes of the viewing zones between the different designs.
Distance emphasis designs require much more accuracy in positioning and the shortest possible vertex distances due to the narrower corridors and/or near zones.
Pay close attention to corridor lengths when the add power is more than +1.50 @ 40cm. Depending on usage, myopes need slightly shorter lengths than hyperopes, especially for the higher dioptric values. Critical for absolute presbyopes.
Wear the lenses to evaluate their performance.
Hope this helps,
Robert Martellaro
At the bottom of the abyss with the alien life forms who fully grok differential geometry I give you contour plots:
https://tinyurl.com/uxdppkkw
I would love to think that. But there are many times where I encounter PAL problems that can’t be solved unless I have more control over the lens.Quote:
Originally Posted by drk
Early 21st century PAL maps.