# Optical Forums > Ophthalmic Optics >  Progressive Prism balancing in Anisometropes

## Iakwin

Hi All,

How should i fit a progressive in a anisometrope who has a such a RX:

R) +2.00
L) -2.00
Add +2.00

The amount of prism will be different in both eyes for definite. I have been always advised that the lab recommends doing the same prism along the PRP.

Does anyone have a good idea of how to fit such Px and still get a high success in progressives? I sometimes adjust the lens nearer to the eyes for closer image size in BE.

I think the progressive designs will be different too in a + lens as compared to a - progressive design. In this case, should freeform lens work better? 

Please give me some pointers  :>

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## Optical Enigma

I would grind no prism in the prp.  Is a slab off required?

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## Iakwin

Hi!!

thanks for your reply.

What is a slab off? do you mean those slabs that appear in Lenticulars?


Please pardon me .  Oops.

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## wmcdonald

.....Bi-Centric Grinding/Slab-off and you will se it is designed to correct the significant imbalace at the reading level. The imbalance in this Rx in the 90th meridian, assuming a 10 mm reading level, is 4^. In the past, this was done on glass flat-tops and required a great deal of hand-crafting. Today it is available on progressive lenses via molding, and becoming more common in the US.

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## HarryChiling

Just a thought, and I don't know if it is even a good idea to do but in a flat top you can use two different segment designs to try to eliminate the prism imbalance.  What about useing two different progressive designns with varying coridor lengths and powers to accomplish the elimination of the prism imbalance.  Has anyone thought of it and if so is it feasable?

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## TPL

I believe this is called antimestropia{oppisite signs/anismetropia is a difference in powers but the same sighn} Please do not take this as nit picking but just wanted to clarify.

In my experiance the first thing I would look at is; what is the patient wearing now as far as rx and a bifocal.

In other words is this rx similar to what they are currently wearing or is it a signifacant change? Are they currently wearing a bifocal and if yes is it aprogressive?If they have a similar situation and are not having double vision you can prescribe without slab-off.

I have fit patients with progressives with slab-off if they complain of double vision at the near{more so with implant patients with a one lens change in a current progreissive wearer}you can try it without slabb-off and see if the patient experiances diplopia/or just order it right at the git go/it all depends on you and your relationship with the patient if they want to aproach it what way as far as evaluating the rx and lens type.

If slab-off is needed order it as REVERSE-SLAB-OFF/your lab can advise as this is becoming the way to aproch grinding slab-off

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## Iakwin

TPL  quote (I believe this is called antimestropia{oppisite signs/anismetropia is a difference in powers but the same sighn} Please do not take this as nit picking but just wanted to clarify.)

Thanks! Learnt something new  ;)

Sadly, i have enquired with the labs and none of them know what is the slab off for progressive. The problem here is that, if the job is too difficult to do, not many labs will want to accept the job. They are very commercialised.

Can you kindly give me some site that provide good write up for slab off for progressives?

Btw, i did a pair of progressives for a antimesotrope some months back.

1st pair, 

did the same amount of prism along PRP
Adjusted the vertex distance as near as possible to reduce image size

Px cannot adapt. Finds distance ok, near is terrible.

Redo a 2nd pair,

Adjusted the prism to be closer on the near progression zone (As compared to the 1st pair)
Now prism are different in PRP and more different in Distant zone than in 1st pair.
Px cannot adapt too.

I used Seiko Back Surface progression lens (Normal Corridor design) for both orders.

Sorry, when you say slab off, it will show as a slab in the progressive lens?? Wouldn't that be quite ugly? Sorry for asking but i have never seen such a lens yet.

Thank you

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## Ory

The correct term is antimetropia/antimetrope.

A slab off lens has a horizontal line across it.  It is not typically too noticable but may be intolerable for someone who wants progressives due to vanity rather than visual reasons.  Apparently some freeform lenses can incorporate the slab off without a noticable line.

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## CME4SPECS

If slab-off is needed order it as REVERSE-SLAB-OFF/your lab can advise as this is becoming the way to aproch grinding slab-off[/QUOTE]

The slab is always done on the concave surface of a pal. Reverse slabs are molded on the convex surface of flat tops and must be surfaced on pals.

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## wmcdonald

......is a term that refers to any difference in refractive power between the two eyes. It is only significant at 2 diopters or more. It is called antimetropia when one eye is myopic and the other hyperopic, but is still a form of anisometropia.

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## ziggy

I would first try to make them with out adding any prism. just order the Rx as you normally would. Most of the time, we can adapt to 2.5 D of imbalance.

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## tmorse

You might try 'SLABS Plus'- 

They are Slab-Off specialists with address:
319 First ST NE
Ruskin, Florida  33570
(813) 649-0225
(800) 237-8501
FAX:(800)552-0957

They slab down to 0.5^ in glass, plastic, Hi-index, Poly with three (3) day turnaround and used to offer 50% off on first order.:cheers:

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## tmorse

I would first try to make them with out adding any prism. just order the Rx as you normally would. Most of the time, we can adapt to 2.5 D of imbalance.

On what facts do you make such a statement?

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## Laurie

Hello,

The Rx has 4.00^ of vertical imbalance at near.  It is highly unlikely that the patient's brain will be able to fuse a single binocular image.  If the patient doesn't get slab off or reverse slab, they will either suppress vision in one eye, alternately suppress vision, have asthenopia (tired, uncomfortable vison), and maybe even diplopia.

The text book criteria is 1.50^ or more.

: )

Laurie

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## tmorse

ZIGGY says: "I would first try to make them with out adding any prism. just order the Rx as you normally would. Most of the time, we can adapt to 2.5 D of imbalance."

Where do people come up with these numbers?

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## foreyesemg

I learned something in CE's about 2 years ago.  I have done this several times and it has worked even on patients that were already wearing slab off.  Reverse the base curves used.  ie...If you use a 4 base on the +2.00 and a 6 base on the -2.00, or even a 3 base on the +2.00 and a 7 base on the -2.00.  Like I said I have had success with this at least half a dozen times in the past year or so.  Not sure exactly why it works but I am sure someone out there would know.  Good Luck

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## tmorse

> I learned something in CE's about 2 years ago.  I have done this several times and it has worked even on patients that were already wearing slab off.  Reverse the base curves used.  ie...If you use a 4 base on the +2.00 and a 6 base on the -2.00, or even a 3 base on the +2.00 and a 7 base on the -2.00.  Like I said I have had success with this at least half a dozen times in the past year or so.  Not sure exactly why it works but I am sure someone out there would know.  Good Luck


Your 'reversing' the base curves would result in a shifting of the two (2)  len's primary and secondary principal planes, such that the respective difference in size of their images would be less apparent, thereby reducing the aniseikonia. But the quality of both len's imaging would become compromised due to the 'irregular' base curve selections. 

However, there would still remain substantial vertical prismatic imbalance (VI) at reading distance for near, so slaboff would still be required in this antimetropia Rx.

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## Jim Mush

Biggest problem here , a bunch of ignorant advice. 
Lots of problems here .  There are nO reverse slabs on progressives. Slabs themselves are stupid on progressives.  You can only match the prism in one spot.  Most patients needing slabs read with one eye. This because most opticians miss the fact that they may need a slab.  If I were despinsing a progressive of this RX, I'd try with out the slab and let the patient read with one eye.  Not explaining this to the patient.  (call it a diservice if you will, but you ever heard of monofit?)  If the patient later complained, I'd then explain the problem in detail and suggest a st!

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## tmorse

> Biggest problem here , a bunch of ignorant advice. 
> Lots of problems here .


Mush should specify exactly what specific post's advice is 'ignorant', and then back it up with facts.:finger: 
Slabs Plus, the 'Slab-Off Specialists' specifically advertises the availability of slab-off on progressives. I personally do not recommend slab-off on progressives for cosmetic reasons. But so what if the VI is balanced at one spot only, that is the case with using ST's as well. 
There is no need to order reverse slab-off at all. Most full service labs can do the old BU regular slab-off.

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## Jim Mush

> Mush should specify exactly what specific post's advice is 'ignorant', and then back it up with facts.:finger: 
> Slabs Plus, the 'Slab-Off Specialists' specifically advertises the availability of slab-off on progressives. I personally do not recommend slab-off on progressives for cosmetic reasons. But so what if the VI is balanced at one spot only, that is the case with using ST's as well. 
> There is no need to order reverse slab-off at all. Most full service labs can do the old BU regular slab-off.


Pretty freaking to try to equalize the imbalance in progressives.  It might have been yours. Somebody accused me of not wanting to slab a progressive for cosmetic reasons.  Crap! I consider optics first always.  Did I hit a sore spot there tm!?? Sounds like it WAS you!  Fix it at only one spot and you may as well have a flat top.

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## tmorse

> Pretty freaking to try to equalize the imbalance in progressives. It might have been yours. Somebody accused me of not wanting to slab a progressive for cosmetic reasons. Crap! I consider optics first always. Did I hit a sore spot there tm!?? Sounds like it WAS you! Fix it at only one spot and you may as well have a flat top.


Looks like MUSH mouth needs therapy.

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## Jim Mush

> Looks like MUSH mouth needs therapy.


OK then there Tmo!  I'll go get me some therapy.  You go get some optical education!

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## chip anderson

My we are getting ugly boys.  Just because you see things differently, no need to get nasty.

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## mullo

tmorse actually provides the education......he is known as the "optical encyclopedia". A very acurate label. I have seen him in "action".




> OK then there Tmo! I'll go get me some therapy. You go get some optical education!

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## Jim Mush

> tmorse actually provides the education......he is known as the "optical encyclopedia". A very acurate label. I have seen him in "action".


  LOL.LOL.LOL.LOL  Butt kisser!:D Just don't let tmo talk you in to slabing a progressive.  It really is a dumb and waistful thing to do.

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## tmorse

> . It really is a dumb and *waistful* thing to do.


Has anyone checked this so-called *'ophthalmologist's???* education
credentials??? :Rolleyes:

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## mullo

Get a life. Troll......




> LOL.LOL.LOL.LOL Butt kisser!:D Just don't let tmo talk you in to slabing a progressive. It really is a dumb and waistful thing to do.

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## Robert Martellaro

> Has anyone checked this so-called *'ophthalmologist's???* education
> credentials???


My guess is an ophtho or optometry student, most likely the latter because opththos know sqaut about optics. 

However, if it wasn't for bad manners, neither one of you would have any manners at all.

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## the dog

I Love To Do Slab Offs !!  The Harder The Better.  I Slab All Materials Except Glass. From Progresives To Flat Tops. A Progressive Lens Is Actually Easier To Craft.  My Only Limitation Is The Ammount Of Prism I Can Grind On My Generator Is 10 Degrees.  I Haven't Seen One That Requires More Than That .  It Would Take A Lot Of Imbalance To Go That Far.

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## Darryl Meister

> On what facts do you make such a statement?


The visual system is actually capable of adapting to quite a bit.

Vertical fusion reserves range from 2 to 4 prism diopters, and research has demonstrated that some spectacle wearers can adapt to as much as 3 prism diopters of vertical imbalance. Further, it is not uncommon for persons to develop an "adaptive vergence," known as _gaze-specific adaptation_, to the differential prismatic effects produced by asymmetric lenses. And all this assumes that the wearer exhibits binocularity at near in the first place, and isn't habitually suppressing one eye.

If the patient is currently symptomatic (exhibiting double vision, asthenopia, etcetera), demonstrates phorias at near through the correction, or has acquired the anisometropia abruptly or later in life, then he or she is more likely to benefit from a slab-off (with either a bifocal or progressive). And progressives will generally induce more prismatic imbalance at near than traditional flat-top bifocals, simply because the distance to the near zone is longer.

That said, I've never seen any evidence to suggest that anisometropes have difficulty adapting to slab-offs. And, in at least one study, anisometropes found that lenses with a slab-off were either comparable to or preferable to lenses without one. Consequently, if you want to err on the side of caution when in doubt, just use a slab-off.

However, I wouldn't recommend using the full prism correction, which is probably overkill in most cases. And if the patient has chosen a progressive lens, which are often purchased for their cosmetic benefit, you would definitely want to recommend an antireflection coating to offset the visibility of the slab line.

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## keithbenjamin

We will often recommend trying an Rx without the slab, if the patient has never worn a slab before and the imbalance is less than 3D on the simple basis of cost (if that is an issue), since patients can often adapt in that range. 

In this Rx you have 4 diopters of prism at 10 mm below OC, however since we're talking about a progressive, as Darryl alluded to, it is important to keep in mind the reading area will be lower than 10mm and you could likely be dealing with 6 diopters or more of prism imbalance at near, depending on your corridor length.

-Keith

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## William Stacy O.D.

> We will often recommend trying an Rx without the slab, if the patient has never worn a slab before and the imbalance is less than 3D on the simple basis of cost (if that is an issue), since patients can often adapt in that range. 
> 
> In this Rx you have 4 diopters of prism at 10 mm below OC, however since we're talking about a progressive, as Darryl alluded to, it is important to keep in mind the reading area will be lower than 10mm and you could likely be dealing with 6 diopters or more of prism imbalance at near, depending on your corridor length.
> 
> -Keith


This is exactly why if you MUST use a progressive in such a case, you MUST use a slab, unless the patient is non-binocular. It's also the reason that for most of these types (aniso more than 3 D.) contacts are the first treatment of choice (and most vision plans will cover them in full as being "medically necessary"), regular lined bifocals are next best choice, and progressives are the WORST choice.  And for what it's worth, I never met an ophthalmologist who understood ophthalmic optics, except one who was first an optometrist.

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## Dave Nelson

There are a number of options presented in this thread, some touted rather agressively, but I see no reference to two other options: 2 pairs of single vision, and dissimilar segments. Now I'm not advocating either in this particular case, but rather presenting all options. Strongly advocating any one method over all others is futile. There are just to many factors to consider before initiating treatment options. The acuities, the degree of disparity. the time of onset, the expected duration of the condition, the hobby and vocational needs, the quality of life, the cost, the waiting time the practicality, ect ect. Maybe single vision readers will keep someone working until their bicentics arrive. Maybe dissimilar segs will solve the problem entirely for one person. Maybe we need to apply the KISS principle. (keep it simple,stupid.) At any rate, ophthalmic pros should have a good fundamental understanding of prism and eikonic disparity, and sound knowlege of a number of different options, and remain flexible when presented with these types of problems. Jumping up and insisting there is only one way to proceed by only looking at the spectacle rx is simplistic, limiting, and not exercising professional judgement.

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## Robert Martellaro

Dave,

You said it. 

Moreover, add "listening closely" to the above... the OP said PAL slabs might not be available in his area, not too hard to believe when you consider that about 25% of the world's population doesn't have safe drinking water.

Regards,

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## William Stacy O.D.

> There are a number of options presented in this thread, some touted rather agressively, but I see no reference to two other options: 2 pairs of single vision, and dissimilar segments.


2 pair is obviously always an option, but was not part of the original post.  Dissimilar segs might have been mentioned, but I'm not sure what dissimliar segs would do for the 4 ^ vertical prism/cm of vertical off center viewing.  Maybe an example of what you're talking about would be helpful.

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## William Stacy O.D.

> Just a thought, and I don't know if it is even a good idea to do but in a flat top you can use two different segment designs to try to eliminate the prism imbalance. What about useing two different progressive designns with varying coridor lengths and powers to accomplish the elimination of the prism imbalance. Has anyone thought of it and if so is it feasable?


You can get a minor reduction by using the wider flat top on the more minus or less plus side, but the wierdness of it to me far exceeds the wierdness of a slab off.  I don't see how different corridor lengths on pals would work at all. The limited area of near viewing with pals would be further narrowed by such an idea.

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## Dave Nelson

Hi William. Harry did indeed refer to dissimilar segments, but referred to using two different flat-tops to eliminate prism imbalance. In fact, one of the segments is usually a round seg, either 22mm round or an ultex and one a flat-top. The method is an old means of correcting a relatively small amount of vertical prism imbalance. It isn't used a lot these days, but can still be a very cost-effective way to bring vertical imbalances to within tolerable levels. It can, and should be another tool in the toolbox for opticians or optometrists. One applies Prentice's rule to the segments only to calculate the amount of compensating prism: thus the method is fairly simple to use. A flat-top has very little prismatic effect or "image jump," due to its design, while a round seg has considerably more due to the distance from the segment edge to its oc. For example, with an add of 2.50, using a ftop-28 on one side, and a 22 round seg on the other. The oc on a 22 round seg is 11 mm, or 1.1 cm from the seg top, giving 1.1 x 2.50= 2.75 bd. Since the oc on the ftop is 5 mm below the seg top, the wearer will be reading 6mm below that. .6 x 2.50= 1.5 bu, giving 1.25 bd on the eye wearing the round seg: not much prism for what may amount to an objectionable cosmetic appearance, but may, again, reduce the total from say 3.00 of imbalance to 1.75, easily tolerable for most people. Some don't care about the cosmetics, and it remains an inexpensive means to bring an imbalance to tolerable levels, either on a permanent or temporary basis.

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## William Stacy O.D.

> A flat-top has very little prismatic effect or "image jump," due to its design, while a round seg has considerably more due to the distance from the segment edge to its oc. For example, with an add of 2.50, using a ftop-28 on one side, and a 22 round seg on the other. The oc on a 22 round seg is 11 mm, or 1.1 cm from the seg top, giving 1.1 x 2.50= 2.75 bd. Since the oc on the ftop is 5 mm below the seg top, the wearer will be reading 6mm below that. .6 x 2.50= 1.5 bu, giving 1.25 bd on the eye wearing the round seg:


Interesting.  Your example means the round seg ht is set about 5 mm higher than the flat top.  To me this means that the patient will have a 5 mm window  where he is looking through a round bifocal and the other eye is still looking through the distance part of the flat top.  Not only that, but he will have two very different amounts locations AND shapes of diplopic "jump" between the two eyes. I can't  imagine anyone getting used to that.  If OTOH you adjust the specs so the lines are more or less coincident, you will eliminate up to half the prismatic benefit.  Slabs are so inconspicuous and trouble free that I just can't understand their avoidance.  They do cost, but not much more than going out for a nice dinner with your honey.

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## Dave Nelson

William, The segments are set at the same hight. The 5mm discrepancy is because the oc on a flat-top is not right at the seg line, its normally about 5 mm below it. The prismatic benefit is derived from the disparity in the distance from the segment top to the oc on each type of segment, and from the very same image jump you indicate would be intolerable. Image jump and prism are one and the same. The amount of prism can be increased by using an ultex type bifocal, but would be quite impractical if that were the case. High segment placement is also an advantage when using dissimilar segments, since less imbalance is created in the first place. In closing, I certainly agree other methods are more practical in most circumstances, particularly the slab off, but dissimilar segments are still a viable option in some limited circumstances.

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## William Stacy O.D.

> William, The segments are set at the same hight. The 5mm discrepancy is because the oc on a flat-top is not right at the seg line, its normally about 5 mm below it. The prismatic benefit is derived from the disparity in the distance from the segment top to the oc on each type of segment, and from the very same image jump you indicate would be intolerable. Image jump and prism are one and the same. The amount of prism can be increased by using an ultex type bifocal, but would be quite impractical if that were the case. High segment placement is also an advantage when using dissimilar segments, since less imbalance is created in the first place. In closing, I certainly agree other methods are more practical in most circumstances, particularly the slab off, but dissimilar segments are still a viable option in some limited circumstances.


If the segs are set at the same height, as in your example, the eye reads 6 mm below the seg top.  That would have to also apply to the round seg, or at a location where the prism is much less than you indicated, and certainly less than that at the seg line.  Prism is not the same as jump.  Jump is the amount of prism at a seg line.  The prism amount 6 mm down from that seg line is quite different, significantly less.  You calculated this correctly for the flat top, but not for the round seg.

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## Darryl Meister

> If the segs are set at the same height, as in your example, the eye reads 6 mm below the seg top.


What Dave was saying is that the vertical prism produced by the flat-top at, say, 6 mm below the ledge (or 1 below the seg OC) is different from the vertical prism produced by the round seg at 6 mm the edge (or 5 mm above the seg OC). Since there is a 6 mm difference between the vertical positions of the two segment optical centers, a vertical prismatic effect equal to 0.6 x Add is induced anywhere in the segments when they are fitted at the same height.

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## William Stacy O.D.

> What Dave was saying is that the vertical prism produced by the flat-top at, say, 6 mm below the ledge (or 1 below the seg OC) is different from the vertical prism produced by the round seg at 6 mm the edge (or 5 mm above the seg OC). Since there is a 6 mm difference between the vertical positions of the two segment optical centers, a vertical prismatic effect equal to 0.6 x Add is induced anywhere in the segments when they are fitted at the same height.


Agreed.

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## Bezza

i recently fitted a patient with considerably more anisometropia than this, i think he was +1.00 ish in one eye and -5.00 ish in the other, with a slab off progressive. It took a fair bit of effort to get it right and we had to drop the slab line from where the lab initially placed it by about 2mm as it was too high and causing double images in his distance vision but when he collected the glasses this saturday he was amazed at how much better they were than his previous flat tops.
Point to remember.....always specify where you want the slab off line to be otherwise the lab will just slap it on the prism reference point.

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## Fezz

Bezza,
Where did the slab line originate on the first pair? Where did you put it on the second. Was it in line witht the fitting cross, horizontal/180 line, or below? I had assumed that it always went with the prism reference/180 horizontal reference point. Thanks!

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## Bezza

> Bezza,
> Where did the slab line originate on the first pair? Where did you put it on the second. Was it in line witht the fitting cross, horizontal/180 line, or below? I had assumed that it always went with the prism reference/180 horizontal reference point. Thanks!


In the first pair the slab line was along the prism reference point, which is the default position, but being a lens design with the fitting cross 2mm above the PRP this was a little too high for the patient to tolerate and so I telephoned the supplier and asked if i could specify where I wanted the slab line placed, they said thatd be fine but that typically the optimum position was at the PRP, so I went ahead and moved it 2mm lower anyway and it worked a treat.

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## Fezz

Thanks Bezza!

:cheers:

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## tmorse

[quote=Darryl Meister;160855]The visual system is actually capable of adapting to quite a bit.

Vertical fusion reserves range from 2 to 4 prism diopters, and research has demonstrated that some spectacle wearers can adapt to as much as 3 prism diopters of vertical imbalance.  

Although we all have a vertical fusional reserve, leading authorities suggest solving for Vertical Imbalance when power difference between OD & OS is one (1) dioptre of more. This might explain why we have a maximum vertical prismatic imbalace tolerance of 0.50^ between two (2) eyes as found in any list of acceptable optical tolerances.:cheers:

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## Darryl Meister

> Although we all have a vertical fusional reserve, leading authorities suggest solving for Vertical Imbalance when power difference between OD & OS is one (1) dioptre of more.


Honestly, I've never really seen any evidence to suggest that 1.0 PD of vertical imbalance will routinely result in symptomatic wearers, and I think this might be overkill. For that matter, many labs won't even try a 1.0 slab-off, and your other vertical imbalance options are limited. And there are certainly thousands of wearers out there right now with more vertical prism imbalance than this at near. Traditionally, the "working limit" has been around 2.0 PD in the US, though many clinicians seem to ignore vertical imbalance altogether anymore.




> This might explain why we have a maximum vertical prismatic imbalace tolerance of 0.50^ between two (2) eyes as found in any list of acceptable optical tolerances


Keep in mind that the vertical prism tolerances used in optical standards are based in no small part on the process capabilities of a typical laboratory, and are not necessarily limited by the acceptable visual "tolerances" of the actual wearer. Besides, if I recall correctly, the vertical prism tolerances proposed by many countries (except the US) for the new ISO mounted pairs standard would actually exceed 1.0 PD for lenses in excess of +/-5.00 D.

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## Dave Nelson

People can tolerate horizontal imbalances far greater than vertical ones, but the allowable tolerances for unwanted horizontal tolerance are very small. It isn't a matter of how much people can tolerate, but how much they should have to tolerate. Deciding when to correct a vertical imbalance is still debated on this board, but there is no real right answer. It depends largely on the acuities, and ocular dominance: a parameter often overlooked by spectacle opticians, but considered by contact lens fitters who practice with bifocal and monovision. I submit we need to give far more consideration to ocular dominance when deciding on our approach to vertical prism imbalances. Note this is entirely different from acuities, but may play as important a role. even assuming equal and normal acuities, the degree of dominance may be an essential parameter in determining the amount of vertical imbalace which may be tolerated by any given individual. Essentially, the more pronounced the dominance, the more quickly and readily suppression can be "activated" or learned. There are many people who are strongly right eye dominant, some who are mildly dominant, (yes I mean their eyes) and some who are somewhat equal, just as people who are ambidextrous with their hands. (I'd give my right arm to be ambidextrous.;) ) Their are a numbr of tests one can give to determine ocular dominance, but the majority of people who are right handed are also right eye dominant. Have the person, with both eyes open, line a pencil up with a distant object while focussing on the pencil. Then have them close their left eye. If the pencil is still lined up, the person is right eye dominant, if the pencil has moved from the distant object, the person is left eye dominant. There are many other factors to consider when determining an action plan for a vertical prism imbalance, as already posted on this thread by myself and others. Never overlook acuities and dominance as parameters to consider as well.

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## Darryl Meister

If the visual system of the patient is capable of binocular fusion and stereopsis, and the vertical imbalance induced by the lenses will result in suppression of either eye, I'd certainly recommend correcting it...

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## Dave Nelson

unless of course, the anisemetropia was a post-op temporary condition, and one was only trying to determine the likelihood of tolerating a given amount of prism imbalance for a given amount of time and the person was balking at paying for something they're not sure they really need...

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## Darryl Meister

Agreed.

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