Heeeelllllppppppp......

[OPTIFREAK]

Can anyone help me?
I am new at optiboard and I was hoping someone could tell me
how to find the decentration of a bifocal or trifocal lens?
If I'm looking for it in the bifocal or trifocal itself? Is that inset?
I'm getting confused as I cannot tell if it is vertical or horizontal that is the decentration?
Simple words as I cannot understand alot of this stuff yet.
Thanks

[uncut]

Welcome to the Forum, OPTIFREAK! I would suggest that you start this thread in the General Optics area, and there you are more likely to get responses. Very good general questions.

regards,

uncut

[chip anderson]

You talkin about a line type bifocal or double lined trifocal?

[Uncle Fester]

Can anyone help me?
I am new at optiboard and I was hoping someone could tell me
how to find the decentration of a bifocal or trifocal lens?
If I'm looking for it in the bifocal or trifocal itself? Is that inset?
I'm getting confused as I cannot tell if it is vertical or horizontal that is the decentration?
Simple words as I cannot understand alot of this stuff yet.
Thanks

What is your specific profession?

[Chris Ryser]

Actually if you ever figured the word decentration in relation to lenses it affects the optical centers, whatever the lens is..............so you have to be more specific. You are supposed to be a professional and what you want to know you should have learned in the optical kinder garden.

[uncut]

Yeah....we are all on a different position on a learning curve.

Working with bifocals is becoming a lost art/skill, even at the laboratory level, IMHO.

OPTIFREAK:
1) When working with a bifocal, determine width of bifocal, divide by 2 horizontally. This becomes your NRP(near reference point). Lay up accordingly(edging) for near OC, or, for checking for accuracy use this point to determine prism(wanted or unwanted).
2) The distance OC is measured/positioned in reference to the segment top line and the NRP and will result in a "up and out" request/ demand for its positioning. This is where the distance OC (monocular) is surfaced/requested as per order, or the position prism(wanted or unwanted) is determined.

The combined result OD and OS creates the accuracy of the finished product.

[hcjilson]

Uncut has taken the time and effort, not only to answer a new member's question, but to give a new member warm words of welcome.

To Chris and Uncle Fester-If you take the time to look, you will find our new member is an ophthalmic tech, which in my experience means an assistant to an ophthalmologist.Their education and training are allied to optics but not necessarily in depth. It would be a good idea to learn more about that profession before questioning credentials or making remarks about a kindergarten education......if you get the drift. Optiboard grows because of new members and becomes stagnant without them. Please keep that in mind when you see a new member.

[tsmith]

Optifreak:

Inset is the horizonal decentration for multifocal segments while drop is the vertical decentration.

These are typically used when manufacturing, and values may be different when laying out for surfacing and finishing and for different machines.

The answer might be less confusing if we knew what context your question is in regards to -lab measurements, analyzing a completed pair of spectacles, etc.

[Uncle Fester]

Uncut has taken the time and effort, not only to answer a new member's question, but to give a new member warm words of welcome.

To Chris and Uncle Fester-If you take the time to look, you will find our new member is an ophthalmic tech, which in my experience means an assistant to an ophthalmologist.Their education and training are allied to optics but not necessarily in depth. It would be a good idea to learn more about that profession before questioning credentials or making remarks about a kindergarten education......if you get the drift. Optiboard grows because of new members and becomes stagnant without them. Please keep that in mind when you see a new member.

Wet noodle beat down duly taken. :)

[WFruit]

Context is important here. Are you asking about finding the drop/inset amount on a semi-finished blank or on a finished pair of glasses? Or how to layout the lens for edging?

If this is something you're going to have to know and use on a regual basis, buy this book: http://www.amazon.com/System-Ophthal...7087949&sr=1-1 It will hep you through A LOT of stuff.

Decentration, by definition, is "movement away from the center," so for Bifocals/Trifocals, your decentration will be both in/out and up/down.

[uncut]

Inquiring minds wanna know!.......did the lightbulb turn on, OPTIFREAK?

[OPTIFREAK]

Uncut :
Same page/different book
I'm trying to find out about the Lensometer
How to Find vertical and horizontal prism in SV/BF(Distance and near) /TRI/Progressive
and how to read the power cross if it's base up and in
Its all about Survival of the fittest
Thanks Hcjilson...

[OPTIFREAK]

Should I go bartend or what?

[hcjilson]

I'm trying to find out about the Lensometer
How to Find vertical and horizontal prism in SV/BF(Distance and near) /TRI/Progressive
and how to read the power cross if it's base up and in
Its all about Survival of the fittest
Thanks Hcjilson...

I don't think it's realistic to learn that on Optiboard. This is something usually taught in the office, or clinical setting.This would usually be taught by whomever is in charge of your tech training.

[pseudonym]

Alvaro Cordova's explanation for neutralizing lenses helped me a lot:

http://www.opticiansfriend.com/main/...of-spectacles/

Post more questions as you think of them. Most who are new to the profession are shameless lurkers. Whatever you're asking is helping someone who has the same question, but doesn't want to be flamed for asking a "stupid" question. I've asked plenty of stupid questions, but they got answered and that's what matters.

[uncut]

Should I go bartend or what?

Heck, yeaah! Stay diversified, a bartending/optical person is highly regarded. Besides, the tips come in handy.

HCJ is right..it sounds like supervision is lacking in your situation, and pseudonym has posted a link to a valuable resource.

The key in finding the prism with any lens using any lensometer is knowing the required OC placement, vertical and horizontal and locating that on the lens or separation on both lenses in the frame. Once this position is ascertained and marked, prism is measured at those points and recorded.

Up and In prism for OD will always be (with eyeglasses front facing you) above the measured point and towards the nasal. The displacement(of the OC) as viewed in most lensometers, will be recorded by viewing the rings which are numbered in increments radiating outwards. Prism can be recorded as a total amount at a particular axis, or using an imaginary rectangle, a combined amount of ___up, and ___in.

[Wes]

doesn't want to be flamed for asking a "stupid" question

Is that why you use a pseudonym? LOL I kid I kid!

[OPTIFREAK]

Thank you so much....

[tmorse]

I suggest you get a bank loan and consider a formal optical education. Take our 6-month program at BC College of Optics and you will soon be answering questions on Optiboard. see www.bccollegeofoptics.ca
Next class begins April 4th, 2011.

[Speed]

This should heeeeelllllpppp.
http://www.ecpmag.com/ce/in-pursuit-of-precision.asp