# Optical Forums > Ophthalmic Optics >  prism in reading segments

## epiclabs

Hi everyone.  I wanted to put out the feelers a little bit on the subject of prism segments.  You see, I work for a specialty laboratory and we construct these segments on a regular basis.  Lately, with a little more emphasis on marketing and education, we have seen a substantial increase in the amount of inquiries and requests for prism segments.  I would like to know if you think prism segments have a logical place in the industry.  What I mean by that is: Is there enough of a need for a product such as a D28 with 5 diopters of base in prism at near only to warrant an all-out marketing campaign?  Please give me your feedback when you get a chance.   Thanks.

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## John R

I guess you are talking about "plastic" lenses here.. We sell glass 30 prism segs and will move about 2 pairs a month as a rough guide.

I can see no reason why not you should market them more. We have seen a few requests here about "plastic" prism segs.

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## sarahr

I would say we have a definite need for prism controlled bifs. There may not be many people requiring 5 prism in at near only but I see people regularly who have mono cataract extraction leaving substantial anisometropia. Slab off, unequal segs + glass lenses are not fantastic but plastics p.controlled bifs are a great idea.

Tell more about your lenses?

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## chip anderson

We will always need these but the cost must be not too much higher than we can do with a Franlin Bifocal.  And the delivery must not be months (the patient requirements can change before you can get some of this stuff out of the lab..

I would not look for the market to be sufficent to have this as my only marked niche.   As an added capability to a lab , yes.  But there aren't near as many presbyopes with squints as there are myopes.


Chip

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## epiclabs

The plastic prism segs that we make are laminated on either the front or back surface of a base lens.  We construct them based on individual needs so we are not limited in terms of prism amount, seg shape or style, add powers, etc.  We can (and have) made prism segments with +5,6,7 add powers and over 12 diopters of prism.  Obviously, these are rare cases, but we have done a number of them in this extreme range in the past.  We currently receive 3-5 jobs/day that require some kind of a multi-component lens where distance and near portions of the lens vary in prism, power or seg location requirements.  I'd say that roughly 50% of those jobs are straight prism segs where we put 3-4 diopters of base in/out prism in a straight top bifocal along with a standard add power of +2.50 or so.  The other 50% consists of varying other modified lenses such as high add spots (jeweler's spots, golfing segs) where we put 10-20mm round +10,15,20 spots on different locations of the lens, plastic quadrifocals, split-powered trifocals (+2 intermediate, +10 near), overviews, prism wedges, etc.  All in all, the business that we've been getting in this area has grown incremently over the past year or so and shows no sign of slowing.  I am really just trying to get a feel for the demand.

To answer your question, Chip, about costs and turnaround times.  I have no doubt that people who have tried to order these products in the past have run into problems in these areas.  I am aware of that perception.  However, in our particular case, we only run jobs of this nature.  Our lab processes 70-80 slab-offs/day, 20-30 extremes (high prism, high powers, myodiscs, etc.), and 3-5 of these multi-component lenses/day.  The point being that these "strange" jobs have a certain flow in this lab.  In most other labs, these jobs are the white elephants.  Therefore, not only are they priced through the roof, but they also become a victim of what I call, "Backburner Syndrome".  These jobs will often sit for weeks upon weeks because they have to be run in a different manner than the rest of the lab's commodity work.  This is the reason you find those month-long delays on work like this.  Most labs are just not set up to accomodate it.  The bottom line is that these jobs can flow through the lab in a matter of days instead of weeks and months.

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## Jeff Trail

As a wholesale lab owner (who has done his fair share of the "tough" odd ball stuff) You have a good idea, most lab owners I know have started using "specialty" labs geared for the odd ball stuff so it does not interfer with the work flow..that includes farming out stinking glass :-) 
  Now as for pushing this I would start with the other labs on that slab stuff, I know a few specialty labs that only deal in slabs and the special stuff and we guys are more than happy to keep them working.. as for advertising near prism and it's uses and educating I'll tell you from my point of view as someone that has been around a few years :-) one of the very best bang for your buck investments is to get a really great speaker and make sure you hit EVERY OD trade show and offer it as a cont. Ed. class .. I know I can tell when my OD's have been to the show in Atlanta and they went to the classes on prism..all of a sudden I get orders for vertical imbalance out the ying yang for a while... amazing how they remember about giving binocular balance testing after a little nudge :-)

Jeff "see's the wholesale market being splintered more and more" Trail

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## epiclabs

Jeff,

I have actually recently become an ABO certified speaker.  I have given 1 seminar for continuing education credit already and it went great.  The response I got from this 1 seminar has been part of the reason for the rapidly growing number of inquiries we get concerning this type of work.  As a specials lab doing sub-contract work for other labs, we already do have a reputation around the lab community so, what I am trying to do is expand that into another product niche.  The main problem that we have found is that there is a bit of resistance from labs to promote this stuff because they don't deal with it on a daily basis.  Slab-offs are one thing, sure.  We get oodles of them every day and will continue to because all labs are at least familiar enough with them to take the order.  In the case of prism segs, however, labs tend to shy away from them because the subject is unfamiliar.  If the labs don't promote them and eyecare providers don't know about them, then that really leaves the specialty lab no choice but to do the educating themselves.  In our case, we deal exclusively with other labs so we have very little contact with the actual eyecare provider.  That's basically the reason I tried Optiboard.  I wanted to get a feel for what people in other segments of the industry feel about the subject. 

Please continue to give me your feedback on this!

Thanks.

JA

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## Jeff Trail

JA

    Another good option to get it out there, have you written anything for any of the industry mags yet? I wrote a couple things for Review of Optometry and Review of Ophthalmology and contributed a number of times to VM stuff... it's pretty simple to get people interested is to send a brief outline to the managing editor, Rich Kirchner (sp) I forget.. is who I dealt with at Review of Opt. ... another good thing is to work with an OD for the Rev. of Opt. and get an MD to work with you in Rev. of Ophth. ... 
     You can also make a simple demo Vid for these guys, no need for high cost production do it yourself stuff works just fine.. I had a 15 min. vid I used to send out years a go to my accounts on any new stuff coming out or things they found confusing.. Your hardest part is going to have to get an OD or MD to do something most are not used to doing, I know of one OD I work with often who is prism crazy when it comes to "near" ... it is going to be an educational thing more than anything.
       I would try to shows... try the industry mags...20/20 and VM might not be the two best for the target you want you need to gear the articles for the refracting side mags.
        The nice thing about it as a a bonus, they PAY you for the articles if they run them ;) You just need to make sure that you write it in a fashion that is "educational" and not just trying to promote your business. That's where making an instructional vid of say your lab process and show some things a long that line and have an OD or MD throw in some stuff and mention that at the end of the article.. or in the Tag line that if they want info how to contact you and send them a free vid. ...
          I can probably think of others but I'm running late and got to get to the grind!!  :Rolleyes:  Oh one other thing, even though it is something that the other "labs" are not doing you need to make sure that they do not feel like they are getting cut out of the loop and that if you do go into the accounts offices you won't be taking the slab work from them (even though you do it already) it's a very competitive biz we work in and cut throat.. we wholesalers are worse than a tank of sharks ;) 
       got ta scoot, got ten minutes to get to work ... maybe others will post some ideas or I'll think of something else today I will add..

Jeff "grind em if ya got em" Trail

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## Lee Prewitt

I really like going through the older threads to see what I have missed.  This one has been really interesting.  I ran across one of theses prism at near Rx's once before.  Really stumped the doc and myself as to how one could grind it.  My question is what are these types of Rx's generally used for?

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## Jubilee

I must say you guys do a wonderful work with your prism segs. I remember a couple of years ago having a gentleman come in to see me who had seven diopters out in each eye. So when it came to reading using his bifocals, no use to him at all. He didn't like to switch between glasses and really wanted something better. He had been searching for an answer for years...had tried ben franklins and the like..didn't like it at all...

It just so happened that in one of the optical magazines Epic Labs was mentioned in specializing in this sort of thing. I was able to talk to the dr and come up with reducing the prism in the seg to only 1 out in each, so it required a 6 diopter in seg. It came back in a week, and my 70 year old retired engineer actually *jumped* with joy!

I really have to agree with the idea on marketing and promoting what is available out there.  Especially as the knowledge and desire lessens for most folks to reach out and do the odd stuff. Heck we have to send out all execs, blendeds, slabs, and most of our other odd stuff. Granted we are an one hour optical, but still most of the odd stuff we could do in the hour if we just had the lens stock or a good drill... If we are scaling back like that, how many other companies are in doing non bread and butter stuff, and as wholesalers get more of this, why do they want to spend a lot of time on high breakage potential jobs?

Go for it! Market it! Educate !

Cassandra

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## Darryl Meister

> *Lee Prewitt said:* 
> My question is what are these types of Rx's generally used for?


Generally, prism is prescribed for bifocal segments because of binocular vision anomalies that either a) occur only during near vision or b) occur with differing magnitudes between far and near vision. For instance, some patients might have eyes that converge too much during near vision for the required amount of accommodation (i.e., high accommodative-convergence to accommodation ratio) or not enough. Consequently, they may need little or no prism at distance, but some prism at near.

Best regards,
Darryl

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## Lee Prewitt

> *Darryl Meister said:* 
> 
> 
>  b) occur with differing magnitudes between far and near vision.


Darryl, are you referring to a slab off situation with this statement?  My understanding from previous conversations was that prism segs dealt with in/out and not up/down?  Also are there specific disease/ocular health issues related with these types of lenses?

Thanks for your wise wisdom!!!

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## John R

> *Lee Prewitt said:* 
> 
>  My understanding from previous conversations was that prism segs dealt with in/out and not up/down?


A prism seg can have any direction you need. up, down, in, out or a resultant axis if you need it..
At least in glass anyway.

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## Lee Prewitt

Thanks for the info John. My you Brits do do alot of glass lenses, don't you???

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## John R

> *Lee Prewitt said:* 
> Thanks for the info John. My you Brits do do alot of glass lenses, don't you???


For my sins yep...Just keeps me of the streets...

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## Darryl Meister

> *Lee Prewitt said:* 
> Darryl, are you referring to a slab off situation with this statement?


Actually, slab-offs are for an altogether different application. You can create vertical prism at near using special bifocal segments or bicentric (slab-off) grinding, but this is most often done to relieve the vertical prism imbalance created by having significantly different distance prescriptions. For instance, if you have a +1.00 D in one eye for distance vision, and a +4.00 D in the other, you will have a total difference of 3.00 D. Now, at 10 mm or so below the distance optical centers, which is about where one would be reading through his or her bifocal segments, that 3.00 D of power difference results in 3.00 prism diopters of vertical imbalance at near. This vertical imbalance (which is up/down) can be relieved by a number of methods, including slab-offs, dissimilar segments, multiple eyewear, Fresnel Press-On optics, R-compensated segments (if they are still made by anyone), etc.

I would think that prism segments nowadays are generally used for binocular vision anomalies -- like esophoria and convergence excess, etc. (usually in/out) -- not for vertical imbalance corrections. While there might still be one or two manufacturers out there who offer the R-compensated ribbon segments (similar to the old Univis lenses) for vertical imbalance corrections, slab-offs are generally the most common method of vertical imbalance correction. It is also possible, as I think John pointed out, to surface your own glass prism-segments, but this does take some "old school" talent that you might not find at that many surfacing labs today.

Best regards,
Darryl

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## Lee Prewitt

Darryl,

The use of slab off I am aware of, I guess my real question now that I have taken additional time to think it through is this....You mentioned usage in  different magnitudes at far and near.  Would this be more akin to dissimilar adds? Say a +2.00 OD and +3.00 OS?  Would this be a situation were one would use vertical prism segs?

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## epiclabs

Hey guys, great conversation going here.  Darryl makes a good point about slab-offs being the main way to combat vertical imbalance problems.  We have had our fair share of requests, however, for up/down prism segs to correct for vertical imbalance.  The one good thing that can be accomplished by doing this is you can eliminate the need for the horizontal "slab line" that runs across the lens.  From a cosmetic standpoint, some people think that eliminating the slab line cleans up the appearance of the final product.  However, when using a prism seg to correct for vertical imbalance, it is almost always going to result in mismatched looking segments.  You are either going to need base up/down prism in one eye only or else a combination of one lens base up/one lens base down.  The end result of such a procedure is a pair of lenses that are not cosmetically similar and much more expensive than the initial slab-off option.  Also, when dealing with prism segs, you are limited to certain materials.  A slab-off, on the other hand, can be ground in any material and will ultimately find its way through the lab cheaper and faster.  

In/out prism segs are an alltogether different situation.  Because you are usually going to be using in/in or out/out prism segs, the segments match very well and make for a cosmetically superior product.

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## John R

> OD  +2.00  +0.25  18
> 
> OS  +2.75  +0.50  3
> 
> Add + 2.50 OU  Prism  2D base in, reading portion only (no prism in the intermediate)
> 
> 7x 28 Flattop (D Seg) trifocal (of maybe bifocal if trifocal not available)
> 
> Sunsensor Gray.


Had someone ask me if this was possible and i remembered this thread.
Can it be done or not.

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## epiclabs

Yes, this can be done.  There are a couple of obstacles to overcome however.  First of all, when using coated, high index materials, we can not laminate prism segs to the front surface of the lens like we could do in regular CR-39.  Instead we would do what we refer to as a Franklin Seg.  We would start by grinding the patient's distance RX in a sunsensor 7x28 trifocal with zero prism.  In addition, we would then grind a pair of D28 sunsensors with +250 adds and include the patient's 2 base in prism.  We would then cut each lens in half, using the 7x28 as the top and the D28 as the bottom.  We'd cut the 7x28 straight between the intermediate and near portions and "replace" the near portion with the D28 with ground prism.  When we cement them together the end result is a 7x28 sunsensor with a +250 add, no prism in the intermediate or distance and 2 base in at near.  The one drawback to this design is the horizontal line that runs through the lens.  Cosmetically, it will look similar to a slab-off or an executive.

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## John R

Thanks for the quick reply.
I will mail of the reply and hopfully they will be in touch with you over this.

Many thanks John R

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