Base Curve Chart Definitions Discussion

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During the LPDS Committee meeting the working group presented their proposed implementation for concise base cure and range chart definitions.  This proposal is outlined in this thread:

During discussions at the meeting representatives from Shamir pointed out that this method does not allow the specification of an allowable base curve range for a specific power combination.  The group requested this topic be started so further discussion could take place between now and our next meeting at Vision Expo West.


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  • 3 weeks later...

Attached sample of Shamir product base chart.

As you can see for some of the Sphere power we have some bases that we can produce but only one of them is the primary.

e.g.: for SPH=-2.00 the primary base is 3.00 and the secundary are base 4.00 and 5.00.

I will be happy to add more information if its not clear.

Autograph III 18 - HI Polar Brown.pdf

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  • 4 months later...

Hi, Anat;

Did you have a proposal for how you would represent the upper and lower limits, as well as the nominal base, for your Rx ranges, using a model similar to what Steve proposed?  At first glance it appears that Steve's proposal could handle this by adding two additional columns for min and max base curve, using the existing column to represent "preferred" base curve, perhaps.  The end result would be more complex and require additional boundary identifiers, but I think it could work.  Is this along the lines of what you had in mind?  (I do not want to presume to speak for you on this, but because this seems to be a Shamir-specific request you might be best able to suggest how this could be represented). 

A design such as you give may not be supported today by all LMS systems; I know in our case we would use upper and lower limits when they are provided by the LDS in response to a BRS request, which is what we do today for Shamir integrations, but we don't have a means of indicating multiple valid ranges of base curves for an Rx when we use a base curve chart.  We can handle a 3-dimensional model, using sphere, cylinder, and add, but only to specify a nominal base. 

Of course, whether LMS systems today can support it does not impact how and whether we represent it in a new standard.




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