Stupid question regarding FT-28 RX

[AlliedJamie]

I have a patient in a -2.00 with a +2.00 add. I understand that the +2.00 cancels out the -2.00 in the RX. However, when I read the bifocal independently, it reads as a plano. Is that normal?
Is the blank made in such a way that the +2.00 add actually cancels out the -2.00 and my seg is a plano? I should know this!!! Thanks for answering!

[jpways]

I hope this is the answer you're looking for but:
The easiest way to think of a line bifocal is to think of it as fusing one lens blank on top of the other (which is one way it used to be made). So if you have 2 lenses of equal, but opposite powers (-1.00/+1.00,-1.25/+1.25,-1.50/+1.50...) The lower segment will always read as plano as that is the total reading power (the same will hold true for lined trifocals and progressives at the NRP)
Similarly a -1.00/+1.25 will read +0.25 when you just read the bifocal segment.

[CME4SPECS]

-2 +2 = zero (plano)

[Oscar]

you're reading the total power through the lens, not the segment itself. You can deduce the power of the seg with some basic math (distance power + seg power = total power) -2.00 + seg = 0 // Seg = +2.00

[AlliedJamie]

I hope this is the answer you're looking for but:
The easiest way to think of a line bifocal is to think of it as fusing one lens blank on top of the other (which is one way it used to be made). So if you have 2 lenses of equal, but opposite powers (-1.00/+1.00,-1.25/+1.25,-1.50/+1.50...) The lower segment will always read as plano as that is the total reading power (the same will hold true for lined trifocals and progressives at the NRP)
Similarly a -1.00/+1.25 will read +0.25 when you just read the bifocal segment.

Thank you! That's how I thought I was understanding it, but couldn't get my brain on board for some reason! LOL

[Uncle Fester]

Remember when you read a high plus multi-focal you need to reverse them in the lensometer to get an accurate add power so the plus lens thickness doesn't create more power than is actually in the add power.

This is related to vertex distances and how they effect powers.

[Don Gilman]

you're reading the total power through the lens, not the segment itself. You can deduce the power of the seg with some basic math (distance power + seg power = total power) -2.00 + seg = 0 // Seg = +2.00

May moons ago when I was in retail we filled Rx's for a local MD and he would always reject them as the add was too strong. I sent him AO's Instruction as you noted and he refused to believe it, so we just filled the Rx a 0.25 weaker in the add. Never complained again. Just one of the reasons I don't miss retail.

[CCGREEN]

May moons ago when I was in retail we filled Rx's for a local MD and he would always reject them as the add was too strong. I sent him AO's Instruction as you noted and he refused to believe it, so we just filled the Rx a 0.25 weaker in the add. Never complained again. Just one of the reasons I don't miss retail.

Way back in my other life when I was a young whipper snapper wet behind the ears in the mid 80's I was working with a OD who refused to believe me when I advised him of the proper way to read a add power. "I'm the Dr." I was told.....well OK, that you are I assured him. I make the glasses you give me the numbers you want and Opticians make it happen. Next day I brought in my old Job Coach from college and showed him in someone else's black and white print that I was correct.
He graciously accepted it and admitted he learned something new to him.
All that being said seems we need to remind the patient that we need to let the Dr do the doctoring and let us Opticians make the glasses.......cause they sure do not want us to do the doctoring and we sure do not want the Dr to try to make a pair of glasses. The patient sees the Dr as all omnipotint and us Opticians just as lowly puttzes. It does not have to be that way if we will take time to train our patient.

[Don Gilman]

Way back in my other life when I was a young whipper snapper wet behind the ears in the mid 80's I was working with a OD who refused to believe me when I advised him of the proper way to read a add power. "I'm the Dr." I was told.....well OK, that you are I assured him. I make the glasses you give me the numbers you want and Opticians make it happen. Next day I brought in my old Job Coach from college and showed him in someone else's black and white print that I was correct.
He graciously accepted it and admitted he learned something new to him.
All that being said seems we need to remind the patient that we need to let the Dr do the doctoring and let us Opticians make the glasses.......cause they sure do not want us to do the doctoring and we sure do not want the Dr to try to make a pair of glasses. The patient sees the Dr as all omnipotint and us Opticians just as lowly puttzes. It does not have to be that way if we will take time to train our patient.

I am insulted.... I am not lowly

[mervinek]

let the Dr do the doctoring and let us Opticians make the glasses.......cause they sure do not want us to do the doctoring and we sure do not want the Dr to try to make a pair of glasses.

YES!!!! A good Dr hires a good Optician and lets the Optician do what they need to do. Support, consult as necessary but mostly stay out.