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How blocked and embedded prism is handled on a job depends upon the particular DS calculatordigital calculator and on the equipment being used. Prism can either be incorporated in the design that is ground onto the back surface of the lens, or it can be blocked on a prism blocker, or it can be a generated by the generator, or it can be some combination of the twothree. Note that, unlike a non-digital job, prism cannot be sent to the generator to be ground as part of the generating process, as what is cut onto the back surface of the blank is the progressive designnot all generators support grinding prism on a digital job. .
The “Blocker Maximum Prism” field deserves explanation as it is used for the DS digital interface. This parameter does not specify a limit for prism to be included in a design (this is determined by the DS processor itself), rather, it operates as a Y/N switch to specify whether the lab supports blocking prism or not. If set to 0.0, then parameter PBOK=0 is sent to the DS digital engine, indicating that the lab will block a maximum of 0 dioptres of prism; any non-zero value will send PBOK=1, indicating that the lab can block some (or all) prism. The amount of prism to be blocked will be sent back to OMICS Rx-Universe in the LMS file in the KPRVM parameter. (Shamir, IOT, Opto-Tech and Essilor all support this method of blocking prism in addition to prism incorporated into the design).Note that the digital vendor must support the use of PBOK - for some vendors, the setting for prism is controlled (or set) by the calculator, and sending PBOK has absolutely no effect on what the calculator calculates.
Prism on the Generator
Some generators permit GPRVM (generated prism) to be sent to used for digital jobs, and others do not. In general, prism will be sent to a generator (GPRVM) for a digital job only if the blocker could not block all prism requested by KPRVM, or if the calculator explicitly sends back GPRVM in the LMS file, thus explicitly asking for a certain amount of prism to be generated.
Beginning in version 6.45.00, a flag can be set on the device setup for the generator, indicating whether prism can be sent to the generator for digital jobs. 
An example will help illustrate how this works.
For a sample job, the digital calculator calculates blocked prism of 6.00 and returns that value in KPRVM in the LMS file:
KPRVM=6.00
The blocker is configured to block a maximum of 4.00 prism, so KPRVM=4.00 will be sent to the blocker. This leaves 2.00 of prism that must be handled by the generator.
If the "Send GPRVM for digital jobs" is set, then the generator will receive GPRVM=2.00, and the final product will thus have 4.00 of prism blocked, and 2.00 of prism generated.
However, if the "Send GPRVM for digital jobs" is not checked, then the job will NOT be sent to the generator, because generating the lens without the required prism would ruin the lens. In this case, the device screen will show "Prsm", and as long as the device is set up to receive a status message, a message will be sent to the generator indicating that "Not all required prism was blocked". The lab may then choose to generator the lens on a generator which DOES support grinding the extra prism required.
Epson-Seiko Calculator
In the case of Epson-Seiko, they support either blocking prism or incorporating it into the design, but not both at the same time. This is controlled by a setting in the Epson-Seiko DS calculator itself. This cannot be selected on a per-job basis, and the Epson-Seiko calculator ignores the PBOK label if sent in the .LDS file, which would normally be used by the LMS to indicate whether or not blocking prism is to be used.
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