Originally Posted by
AndyOptom
Lots to unpack and understand here (for me, at least), hope you don't mind the further inquiries :)
Ok, noted.
Be that as it may, how does this design functionally differ from a progressive with a 20 mm corridor? One continuous curve or not, once a progressive corridor gets that long, they're smoother than the usual anyway (as with certain office progressives whose designs are basically one extended corridor running through the entire vertical of the lens, those definitely don't feel like a no-line trifocal, as you describe).
Regardless of how a lens design is accomplished mechanically (PAL as a no-line trifocal with an extra long corridor versus NAL with this single continuous curve), how much is the perceived improvement when placed in front of the end user's eyes? Compared to a progressive of equivalent corridor length?
Doesn't matter that whatever the NAL uses is not a corridor, how does it measure up functionally and feels-wise versus a corridor that gets stretched out that long (therefore widening and further softening the PAL anyway)?
So if an NAL wearer is looking through the upper part of the corridor/curve (intended for about 20 feet), they can also see clearly a fixation target within about arm's length (supposed to be only viewable through the lower part of the corridor/curve, if we were talking about progressives)?
Therefore the entire corridor/curve can work for any distance between 20 to 1 feet, and the wearer doesn't have to look down to fixate closer?
That is the impression I get when you say the NAL corrects for all distances in a way PAL cannot.
Otherwise, no-line trifocal or not, PAL also correct for all distances. Just using a shorter corridor (and therefore with a narrower FOV + more swim).
Various progressives also have built in design features with the same stated aim, so my initial question remains:
Design etc aside, has the NAL been compared side by side with a progressive of equivalent above average corridor length? And if so, which designs + what were the results? The white paper makes no mention of this.
Otherwise, beg pardon for me saying so, this sounds like how the bigger labs compare a brand new freeform progressive design in high index with multicoat to a bog standard molded design uncoated in CR-39.
Don't get me wrong, I'm all for innovation and advancements in lens technology, and routinely dispense PAL, multifocal contact lenses, bifocals, you name it, for purposes other than their actual intended designs... as long as to the patient, the vision + function provided meets expectations + requirements. So this NAL has definitely piqued my curiosity, although I'd definitely subject it to the same professional skepticism I would any new lens from any lab (all of my regular lens reps know, if they can't at least clarify such details reasonably to aid the fit and dispense, I'm not selling those products).
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