Am I out of line thinking that 4+ diopters of prism should be possible in a digital progressive? Why can't my lab do it? Do I have to send them cookies as a bribe or is it just implausible?
Am I out of line thinking that 4+ diopters of prism should be possible in a digital progressive? Why can't my lab do it? Do I have to send them cookies as a bribe or is it just implausible?
I've got one that can - in deference to Optiboard rules - pm me.
Depends on the design you're talking about. Some designers limit the prism, but I've been able to get up to 10 or so with some of them. It can also depend on frame/material/blank availability, but just being a digital lens shouldn't cause an issue.
Digital or Freeform?
Digital or Freeform!
Big confusion these days I think...
I know Shamir told me to use the spectrum for SV or PAL prism, not Autographs because of something about POW compensation being thrown way off with the introduction of prism
Most companies can go up to four per eye. It's probably more of a machining limitation than anything else.Originally Posted by chaoticneutral
Or you could up the bribe to steak and whiskey.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
The fancy digitals have so many complicated layers of calculations going on that excessive powers end up compromising the quality of vision in the advertised channel width.
Had a patient prescribed 5 diopters of prism in each eye placed in a dual-side digital progressive. When he got bumped up to 7 diopters of prism OU, it was out of range for the same progressive--had to drop him down to an older version progressive--still digital but not enhanced.
The labs I've worked with make estimations (based on costly trial and error experiences) about how far they can push the ranges...And get good results a cost-effective proportion of the time. They have no incentive to say 'yes we can' if it usually takes several sets of lenses to eek one out that passes. They gotta earn a living, too.
But the good thing about lab guys--they innately Want to try it just to prove they can! So a bribe isn't a bad idea...
I tried to bribe them with steak and Crown, they said no thankyou which is just plain unamerican even tho Crown is Canadian. I was looking for 5 BI ou, they said cannot be done. I say hogwash!
As stated above, it depends on the design. Some digital lenses (such as the Varilux "enhanced") series use blanks with part of the add already molded in. That is why it is digital and not free form. Those blanks only come with a set thickness value and blank size. If the inset or seg height of the frame is more than a minimum amount, it might cause cut out issues.
Another thing to note is many of the big name manufacturers require their designs to be used on their specific branded pucks. So even on a true free form with both front and back side surfacing, cut out can be an issue if they can't get extra thick pucks.
Of course certain scripts and prism combos do make it more feasible than others. However sometimes it is hard explaining to accounts why you could do it with one script, but not another. So many just make the decision to draw a line and not cross it.
"Some believe in destiny, and some believe in fate. But I believe that happiness is something we create."-Something More by Sugarland
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