troubled and stumped
problem: pt. in shamir 2 att 7 base with +1.75 sph and 2.25 add. has same rx in clear but no high wrap and sees great. current seg is 23 and that is dropped 1.5 mm to maximize dist rx... is that right?? seg is right on but has to tilt head back to see clear. by me dropping seg 1.5 mm is that bringing in distortion?? i wouldn't think so. any ideas?
David,Originally Posted by davidhd
Is this a polarized lens? BC should be about +6 or +8, but a polarized blank might read closer to +7.50 if you ordered +8. Make sure you have the 18mm version and not the 15mm minimum fitting height. An incorrect fitting height (above or below center pupil) combined with high tilt values might blur the distance slightly. Make sure that the POW (as-worn technology) is measured, instead of using the default values. Evaluate the distance vision at infinity and outdoors (or through a large window on a bright day) if polarized.
Hope this helps,
Robert
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.
thanks for replying, I do appreciate it. Well, he is in a polarized but i checked b.c and it's clocking in at 7. so i think that is not the issue. I did however, drop 1.5 mm and i realized that on shamir or any pal blanks there is a 4 mm drop, this plus my 1.5 mm drop is too much and is bringing in distortion to his distance, hence the tilting of the head back to get a clear zone. I remembered this at 4 am, woke up in a cold sweat and peacefully went back to sleep. thanks for the response. I hope this solves the problem. We will see when he picks up.
You're welcome. The reason I brought up BCs is that the Auto 2 Attitude comes in a +6 and +8, and I was concerned you might have an off-spec or counterfeit lens.
The 4mm "drop", or the distance from the Fitting Point to the Prism Reference Point has no direct effect on the corridor length or where the corridor starts relative to the Fitting Point. I've seen long corridors with no drop, and very short corridors with a 4mm drop. What matters is the design, not the placement of the reference points. Most PALs have a 4mm separation, but there are some that have the FP on the datum line, some are 6mm above.
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.
Actually that's not true. I know this will surprise most people, but by Shamir's base curve charts (depending on material), the Autograph II Attitude can be on anything between a true front curve of 4.50 to 10.50.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
Six, seven, and eight, all materials, according to Shamir. I didn't know about the seven base. I really, really didn't know about the four and ten. I've never seen a four base wrap, but I suppose you could tilt one more than twelve degrees. So is this new, or off-label?
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.
Neither. The chart you posted is for the 1.67. If you pull the chart for the 1.58 (Poly) it will show the other bases.
And just as soon as I figure out how, I'll post it so you can see it....
Last edited by WFruit; 08-03-2013 at 03:13 PM. Reason: forgot what the index of poly is....
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
I'm not trying to be sneaky. I said:
because that's what Shamir's charts show.Six, seven, and eight, all materials, according to Shamir. I didn't know about the seven base. I really, really didn't know about the four and ten. I've never seen a four base wrap, but I suppose you could tilt one more than twelve degrees. So is this new, or off-label?
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.
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