Doesn't my lab know this is ugly?

[icare]

This is a -6.00 carrier poly FT28 in a 44 eye child's frame with a 27 B height. The seg ht is 18. A CT of 1.5mm was ordered. I don't know why my lab insists on setting the carrier OC 5mm above the seg, like it's an Autoflex 1 in a 59 eye. Could they be stuck in the 1960's? I ordered uncuts and this is how it finished out. Sorry the photos are not more ideal.

If you look at the photos, you can see that the top edge at the eye wire is about 1.5mm thick and the bottom edge at the eye wire is probably 7 or 8mm thick. I've asked this well-known lab in the Wilkes-Barre PA region to set the OC at the top of the seg before, but they don't seem able or willing.

Am I correct that this could have been better? Shouldn't a modern lab recognize how these small eye FT's will look when they're finished?

Thanks for looking. :)

[Fezz]

Somebody goofed. Bigtime. You got more than poor cosmetics going on there.

[HarryChiling]

I am assumeing that it is for a child and the seg splits the pupil. Why not when ordering specify the correct amout f prism with the Rx so that the OC falls on the seg line. Not too dificult and you get the job done, it is unfortunate, but also the cost of an uneducated industry. The people in the lab would probably not know what to do if you said grind the OC on the seg line :hammer: , but if you say 3 dipters Base up with the Rx for instance they know how and where to punch all that info into their systems.

[MarcE]

I am assumeing that it is for a child and the seg splits the pupil. Why not when ordering specify the correct amout f prism with the Rx so that the OC falls on the seg line. Not too dificult and you get the job done, it is unfortunate, but also the cost of an uneducated industry. The people in the lab would probably not know what to do if you said grind the OC on the seg line :hammer: , but if you say 3 dipters Base up with the Rx for instance they know how and where to punch all that info into their systems.

Yea, but now they will charge you $18 for prism. And I don't care to figure out how much prism thinning to specify. I also have had this problem, but never to this degree. I have only specified the OC position a few times, but it doen's matter. It will be 4mm above seg, no matter what I spec. Shouldn't this FT including prism thinning? I get it on my progressives without asking for it. FTs shouldn't be discriminated against just because Chris Reyser prefers them.:bbg:

Well, off to bed, these damn no-line lens thingies that my Dr put me in give me headaches when I use them at the computer.

[HarryChiling]

Yea, but now they will charge you $18 for prism. And I don't care to figure out how much prism thinning to specify.

They charge you for prism and you call your lab rep and tell them why you did this and they nock it off or lose your business, I would question wheather or not you would want to do business with them in the first place if this is the ork you are getting, as for how much prism come on prentices rule couldn't be more simple.

Prism = Power * Decentration (cm)

You said your lab grinds it at 4mm above seg and lets say you want the OC on the seg line and the power is -6.00:

Prism = (-6.00) * 0.04 = 0.24 round it to 0.25 base up. If thats too hard then send them to my shop, I will calculate the prism and the bill and I will fo it all in my head. (ringling brothers here I come).

For prism thinning

This is a -6.00 carrier poly FT28 in a 44 eye child's frame with a 27 B height. The seg ht is 18. A CT of 1.5mm was ordered.

so lets figre out what the thickness is in the top of the frame and the bottom seg height is 18 and the OC is geerally ground 5mm above the seg line so the OC is 22mm from the bottom of the frame and 5mm from the top
Sag=[D*(d/2)^2]/[2000(n-1)]
top = [6.00 * (5mm)^2 / 2000 (1.589 - 1)]
top = [150 / 1178]
top = 0.13 + 1.5 = 1.63

bottom = [6.00 * (22mm)^2 / 2000 (1.589 - 1)
bottom = [2904 / 1178]
bottom = 2.47 + 1.5 = 3.97

so the difference is 2.34 mm at the bottom, which we will split and add to the top.

t=[d*P/100(n-1)]

1.16mm = [27mm * P / 100 (1.589 - 1)]
[1.16mm * 100 (1.589 - 1)] / 27mm = P
1.16 * 58.9 / 27 = P
P = 2.53 Base Up would put the OC on the GC.

MarcE, if you don't care why would you expect your lab to care?

[cocoisland58]

I wouldn't have cut them. Our lab will call us when they think something isn't going to work out right and they make suggestions. On the other hand something like this coming out of the vsp lab is not that unusual.

[Joann Raytar]

I thought the lab you are talking about had space on their order form to enter a BOC? No math involved; do you think they would still charge you?

[jofelk]

This is a -6.00 carrier poly FT28 in a 44 eye child's frame with a 27 B height. The seg ht is 18. A CT of 1.5mm was ordered. I don't know why my lab insists on setting the carrier OC 5mm above the seg, like it's an Autoflex 1 in a 59 eye. Could they be stuck in the 1960's? I ordered uncuts and this is how it finished out. Sorry the photos are not more ideal.

If you look at the photos, you can see that the top edge at the eye wire is about 1.5mm thick and the bottom edge at the eye wire is probably 7 or 8mm thick. I've asked this well-known lab in the Wilkes-Barre PA region to set the OC at the top of the seg before, but they don't seem able or willing.

Am I correct that this could have been better? Shouldn't a modern lab recognize how these small eye FT's will look when they're finished?

Thanks for looking. :)

First, we are not the lab that made this Rx, but I will give a labs perspective on your problem.
You would not be able to read the Rx if the OC were at the top of the seg. On poly Ft there is about a 3mm area above seg that would produce an abberated Rx.
A "modern lab" does know how the finished product would look, but we fill the Rx as given to us, which is not always "pretty".

[Fezz]

but we fill the Rx as given to us, which is not always "pretty".

Jofelk;

From a labs perspective, how should something like this be ordered?

Your insight and lab knowledge would be helpful so this kind of garbage could be avoided.

[icare]

Jofelk;

From a labs perspective, how should something like this be ordered?

Your insight and lab knowledge would be helpful so this kind of garbage could be avoided.

Ditto.

Thank you, all, for your thoughtful replies. My lab has no BOC specification on their standard form. Knowing how to circumvent this without incurring a prism charge would be great.

I'm not sure if I'm going to direct my lab to this thread or not. They need to know and they need to know the hard way.

icare

[Fezz]

We could always form a group "The Optiboard Pests" and barrage them with phone calls and endless questions about prism and fabrication questions until they give up and decide to get proactive and do the right thing!

[optical24/7]

First, we are not the lab that made this Rx, but I will give a labs perspective on your problem.
You would not be able to read the Rx if the OC were at the top of the seg. On poly Ft there is about a 3mm area above seg that would produce an abberated Rx.
A "modern lab" does know how the finished product would look, but we fill the Rx as given to us, which is not always "pretty".

I'm sorry but I don't buy this explanation. How many progressives come in with the OC's in the distance verification zone? Almost none. You still can varify power though you have vertical prism OU.

I would explain to my lab that if they were unable to put the OC's at the seg line I'd be seeking another lab.

[jofelk]

I'm sorry but I don't buy this explanation. How many progressives come in with the OC's in the distance verification zone? Almost none. You still can varify power though you have vertical prism OU.

I would explain to my lab that if they were unable to put the OC's at the seg line I'd be seeking another lab.

We need to look at the design of a flat top. The problem with FLAT TOPs, and poly is the worst, is the ledge. Trying to grind an OC at the seg line often causes the "abberated" appearance. If you would read the Rx further up it would most likely read OK. My experience is that most opticians when checking the Rx will check the power at exact center. If we put the center 3-5mm above the seg line the Rx reads much clearer.

[gemstone]

I'm sorry but I don't buy this explanation. How many progressives come in with the OC's in the distance verification zone? Almost none. You still can varify power though you have vertical prism OU.

I would explain to my lab that if they were unable to put the OC's at the seg line I'd be seeking another lab.

Jofec is talking about coating buildup and irregularities. This is on ploy and most coated flat tops. The coating is much smoother on progressives.

As for advice: This is more common than you think. Almost every time the seg is decentered up the lab will grind the oc above the seg so the inspecting dispensers can get a decent reading of power. Same with plus except the thick part is on top. Most often it is not bad enough to cause a noticeable problem. (dispensers don't take a close enough look to spot this.)
When you get one like this, and usually you will have this product in your hand because you had no idea what you were ordering, this is what you do.

1. Call the lab manager and tell him what happened. (you can send it to them with a note to call if you prefer, that way they will have it in their hand when you are talking to them.)

2. Tell them you would like it ground so the oc is centered vertically in the frame. (In this case that would be 4.5 down into the seg or 13.5 hi.) If the lab manager can't understand or handle this call another lab. (If you don't understand or can't figure this, don't sell the glasses.)

3. Make a detailed note on the record.

This works almost all the time. A pair of lenses will be waisted. This is the nature of the business.

[jofelk]

Jofec is talking about coating buildup and irregularities. This is on ploy and most coated flat tops. The coating is much smoother on progressives.

As for advice: This is more common than you think. Almost every time the seg is decentered up the lab will grind the oc above the seg so the inspecting dispensers can get a decent reading of power. Same with plus except the thick part is on top. Most often it is not bad enough to cause a noticeable problem. (dispensers don't take a close enough look to spot this.)
When you get one like this, and usually you will have this product in your hand because you had no idea what you were ordering, this is what you do.

1. Call the lab manager and tell him what happened. (you can send it to them with a note to call if you prefer, that way they will have it in their hand when you are talking to them.)

2. Tell them you would like it ground so the oc is centered vertically in the frame. (In this case that would be 4.5 down into the seg or 13.5 hi.) If the lab manager can't understand or handle this call another lab. (If you don't understand or can't figure this, don't sell the glasses.)

3. Make a detailed note on the record.

This works almost all the time. A pair of lenses will be waisted. This is the nature of the business.

Good advice. I thrive on problems to a fault. If an account wanted to contact me with this problem I would explain the situation an offer solutions. In this case you could put the OC at the geometric center of the "B" measurement. I would explain the amount of prism induced and a possible problem with it. Strange cases have options and "side effects".

[icare]

Tell them you would like it ground so the oc is centered vertically in the frame. (In this case that would be 4.5 down into the seg or 13.5 hi.) If the lab manager can't understand or handle this call another lab. (If you don't understand or can't figure this, don't sell the glasses.)

This is a beautiful reply. And the 'don't understand' comment is a delightful caution to the unwary.

I had given thought to the OC centered in the frame, too, imagining it below the seg height. I'm glad to know that this is a reasonable request.

Maybe I should just order with the B specified and tell them that the OC should be centered vertically in the frame. Is that a clear instruction to the surfacers? Certainly a conversation with the lab is in order. I'm glad I have my ducks in a row before starting that discussion.

Thank you very much.

Oh, and one other issue - this is a Transitions Polycarbonate Flat-Top. Would that pose any additional concerns?

[HarryChiling]

You would not be able to read the Rx if the OC were at the top of the seg. On poly Ft there is about a 3mm area above seg that would produce an abberated Rx.

You are right, but if this is a child and the doctor called for splittng the pupil the child will be looking out of this very same spot no matter where the OC is ground. To get the OC on GC the formulas is given in the preceeding posts and you should make sure to factor in the other eye and have ground the same amount of prism in both eyes.

[jofelk]

You are right, but if this is a child and the doctor called for splittng the pupil the child will be looking out of this very same spot no matter where the OC is ground. To get the OC on GC the formulas is given in the preceeding posts and you should make sure to factor in the other eye and have ground the same amount of prism in both eyes.

Please read follow up posts to this problem.

[optical24/7]

[quote=gemstone;179356]

2. Tell them you would like it ground so the oc is centered vertically in the frame. (In this case that would be 4.5 down into the seg or 13.5 hi.) If the lab manager can't understand or handle this call another lab. (If you don't understand or can't figure this, don't sell the glasses.)


quote]


This will not always work if you have a vertical power imbalance at 90 degrees. Say you put the OC 4 below the seg line but the patient is viewing distances at 4 above. With an imbalance of 2 diopters of power you will induce 1.6 degrees of prism imbalance between OD and OS at distance, even more if the patient views higher than 4 above.

I agree jofelk, many opticians try to check powers at the OC. But the general rule of thumb when dealing with children in bifocals is to split the pupil. This usually means the seg hgt. will be at or above geo center of the B. The ideal is to have an optician knowledgeable enough to make a good frame selection in the 1st place with the seg line as close to the geo B as possible and have a lab to put the OC at seg line. If an account calls about not being able to read the power at OC, instruct them to verify power and imbalance above the seg line, the same way they do with progressives.

I feel for you. I've run several large labs and it's amazing how many opticians I've had to educate on the relation of frame selection versus the Rx.

[gemstone]

[quote=optical24/7;179366]

2. Tell them you would like it ground so the oc is centered vertically in the frame. (In this case that would be 4.5 down into the seg or 13.5 hi.) If the lab manager can't understand or handle this call another lab. (If you don't understand or can't figure this, don't sell the glasses.)


quote]


This will not always work if you have a vertical power imbalance at 90 degrees. Say you put the OC 4 below the seg line but the patient is viewing distances at 4 above. With an imbalance of 2 diopters of power you will induce 1.6 degrees of prism imbalance between OD and OS at distance, even more if the patient views higher than 4 above.

I agree jofelk, many opticians try to check powers at the OC. But the general rule of thumb when dealing with children in bifocals is to split the pupil. This usually means the seg hgt. will be at or above geo center of the B. The ideal is to have an optician knowledgeable enough to make a good frame selection in the 1st place with the seg line as close to the geo B as possible and have a lab to put the OC at seg line. If an account calls about not being able to read the power at OC, instruct them to verify power and imbalance above the seg line, the same way they do with progressives.

I feel for you. I've run several large labs and it's amazing how many opticians I've had to educate on the relation of frame selection versus the Rx.

In MOST cases this will work. True, you should consider the imbalance if any is created by power differences.

[jofelk]

I think we have come to the conclusion that with any solution, a new problem is introduced. Another conclusion is the need for COMMUNICATION.

[CDOT]

Easy answer: ....lab note: O.C. on Datum... and its a done deal:D

[gemstone]

Easy answer: ....lab note: O.C. on Datum... and its a done deal:D

I like to know at how many labs this would be effective. I'd guess,

75% no effect
20% would call to find out what you mean
5 % you'd get your desired effect

Test your lab. Without warning.

[HarryChiling]

I agree jofelk, many opticians try to check powers at the OC. But the general rule of thumb when dealing with children in bifocals is to split the pupil. This usually means the seg hgt. will be at or above geo center of the B. The ideal is to have an optician knowledgeable enough to make a good frame selection in the 1st place

So true the frame has to be a good fit for the Rx, but with children sometimes the frame has got to be what the frame has got to be. It is unfortunate, but with a child it is almost more important to have the child like the frame and want to wear them than to have the right frame. It is a difficult dance in the office, because you have to hype up the frames that would work best and try to stear them clear of the junk with all the beads and garbage on it that seems to atrack the kids.

Easy answer: ....lab note: O.C. on Datum... and its a done deal:D

Definately the right way to do it.

I think we have come to the conclusion that with any solution, a new problem is introduced. Another conclusion is the need for COMMUNICATION.

You are right, communication is the key, but often times the optician does not know that the glasses are going to look like this untill they have them in their hands, then it's a problem, the lab also doesn't have the time to scrutinize every Rx and call to OK the job before making it. I think the need is for EDUCATION and COMMUNICATION.

[icare]

Easy answer: ....lab note: O.C. on Datum... and its a done deal:D

OK, here comes my unfortunate query....

What is Datum?

I'm with gemstone on which labs will proceed properly. I've written OC at top of seg numerous times and have had nil effect on the outcome. The job pictured is just the extreme of what I've encountered and it really miffed me.

I'm almost certain that I've seen more 7x28's and 7x35's with the OC much closer to the seg. I like the prism specification idea, too, but the extra cost would be tough to endure.