Originally Posted by
Robert Martellaro
Correct.
Sure, especially with higher Adds and large disparities in corridor lengths, or in this case the "B" dimension. Some will grin and bear it- "I guess that's the way it has to be", some might not notice, some will complain, others might not come back at all, ever.
For example, my present frame has a 30mm B, with a 20mm fitting height. I tried a highly respected, excellent quality, variable freeform PAL and found the near vision wanting- I had to lift my chin to see small text clearly, and was constantly raising my chin to read the paper at the dinner table. It was a variable design, and the software defaulted to longest corridor. There was no way to specify the corridor length, so the only way to get the near performance I desire is to choose a narrower frame, which would put the bottom of the lens and/or frame right in the middle of the bottom of the page. No thanks. My question here would be, why go with the variable design? At that height, with that B dimension, it would be unecesary; the fixed height 18 would have served you better. On the other hand, the software should not have defaulted to the longest corridor, that may be a software issue on the lab's end.
Another scenario is an advanced presbyopic moderate myope who takes off their glasses when reading, chooses a frame with a 25mm B, but wants the best possible on and off-axis distance vision, with good intermediate for the automobile, with some near utility. The software now chooses a very short corridor, resulting in compromised (for some) distance night vision, blurred off-axis distance vision, and a very dynamic and "busy" lens. It's not what the wearer wants or needs, and they paid dearly for a lens that under performs. A Sola VIP would've offered better distance performance at one third the price. The software would only choose a very short corridor if the seg ht demanded it, for example if the seg were at 11.... in which case the fixed ht 11 would have the same issues. A better result might be to order a higher seg ht fixed, say 13 and edged the lens lower. A VIP would only provide better performance if the seg ht were much higher, say 18~20... in which case the software wouldn't default to the shortest corridor length for the Variable design.
IMO, the variable designs are for the trainees and/or busy, insurance driven dispensaries that don't have the skills or the time to do it right. Given the complexities of insuring proper fit with the Variable, I would say that it is absolutely NOT for trainees, nor for offices that "don't have the skills."
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