# Optical Forums > Progressive Lens Discussion Forum >  Anisometropia PALs?

## stanley_tien

Besides Individual PALs, does any lenses suitable for anisometropia patient? Zeiss ? Varilux? Hoya? SOLA?

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## chip anderson

Surely you jest!

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## stanley_tien

hi Chip, 

I mean most suitable for anisometropia

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## eyepod

Hmmmmm.  Anisometropia is anyone with a diopter or more difference from one eye to the other.......pretty common.  Is there a specific Rx you can give us?  Is the difference huge?  One eye myopic, one hyperopic or with a lot of astigmatism?  More information may help.

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## drk

It all comes down to corridor length.  Go short corridor.

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## stanley_tien

Hi Eyepod,
R -1.50
L-0.75 
Add+1.50 
Patient used to have Vx.Physio, feel uncomfortable at intermediate?

By the way,could you guys tell me more about anisometropia patient which PALs more suitable for those patient with huge different power,One eye myopic, one hyperopic and with a lot of astigmatism

i mean which PALs suitable in which cases

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## drk

Actually, the definition of anisometropia is a 2D difference in sphere or more than 1D difference in cylinder (especially oblique axes). 

This does not meet the criterion. 

Sure, anyone can have imbalance problems, but this doesn't look sufficient to cause a problem.

Any discomfort in the intermediate is more likely due to improper fitting issues, or lens design limitations, or unrealistic patient expectations.

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## au

Hi drk,

very good explaination !

if for the case, I definitely choose short corridor PAL, because easy for 1st PAL user to learn.

:cheers:

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## eyepod

> Actually, the definition of anisometropia is a 2D difference in sphere or more than 1D difference in cylinder (especially oblique axes). 
> 
> This does not meet the criterion. 
> 
> Sure, anyone can have imbalance problems, but this doesn't look sufficient to cause a problem.
> 
> Any discomfort in the intermediate is more likely due to improper fitting issues, or lens design limitations, or unrealistic patient expectations.


 
drk,
 You are so right.  My goof.  The books are pretty dusty.  One of these days I'll learn to verify mt "facts" before I post them.  DOH! :hammer:I agree with all of the other stuff you said too.  And with an expert like me behind you.......................

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## drk

:):):):)

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## Metronome

Delete this post.

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## Bobie

Stanley ,
Please try Varilux Comfort.

In case that you would like to have better , please go for TOG Excilite Freedom 15.

In case that you would like to have even better , please go for Hoyalux iD 14 or Rodenstock Multigressiv ILT.

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## Bezza

Where there is only one or two dioptres of anisometropia it usually does not cause a problem, although some patients will notice that the vision is slightly better in one eye.
Using a short corridor lens or an individual design are both great options for these patients, although when there is a significant amount of anisometropia neither will suffice as the patient will be unable to fuse the two retinal images due to the difference in spectacle magnification and the amount of differential prism induced when looking through a point away from the optical centre. 
In these cases a slab off is the only viable solution if you intend to fit a progressive. Don't be scared to fit slab-off varis for anisometopes either, the ones i have fitted have said that they are much better than their previous slab off bifs. It's a tricky task, you have to be very accurate with your measurements and remember that you can specify where you want the slab line to be (in between lower limbus and lower pupil margin seems to be the sweet spot) but it is very satisfying when you get it right.

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## Diane

> Actually, the definition of anisometropia is a 2D difference in sphere or more than 1D difference in cylinder (especially oblique axes). 
> 
> This does not meet the criterion. 
> 
> Sure, anyone can have imbalance problems, but this doesn't look sufficient to cause a problem.
> 
> Any discomfort in the intermediate is more likely due to improper fitting issues, or lens design limitations, or unrealistic patient expectations.


Drk,

Interesting topic...I'm wondering which book states 2D difference in sphere or more than 1D difference in cylinder (especially oblique axes).  I can't find that particular statement.  As a matter of fact, the books I have, state as eyepod stated by definition.  However, I agree that 1.00D is not usually a problem.  The problem arises when you look at the total powers in ANY meridian and how much difference there would be.  That would require placing the Rx on a lens cross and even using Prentice's rule to determine the power in any meridian of gaze.  Since the thread is about PAL's, I wouldn't see a problem with the patient in question, since regardless of the meridian in the sphere power, there is insufficient difference to cause prism imbalance.  

Just wondering.  I love this topic.:)

Diane

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## Bobie

Free Form PALs is recommended for anisometropia.

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## Andrew Weiss

I just dispensed a pair of Zeiss Individuals to a patient with the following Rx:

R: -1.25 -3.75 x 092, 1.0 prism down
L: -6.75 -2.00 X 090, 1.0 prism up
Add 2.50

She had been wearing progressives before with some difficulty.  She put on the new ones and loved them immediately.

For years I relied on Rodenstock's Multigressiv II as my "go-to" lens for anesometropic patients who insisted on having progressives.  Since it was discontinued, I've been using the Zeiss Individual and Individual Short with similar success.

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## OPTIDONN

> Free Form PALs is recommended for anisometropia.


OK I'll bite. How do free forms work better with verticle imbalance or unequal image size?

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## Bezza

_Anisometropia_ is defined simply as an unequal refractive error as opposed to _isometropia_ (equal refractive errors) or _antimetropia_ (opposite refractive errors) which is a case of anisometropia where one eye is + and the other is -. 
In the strictest sense anisometropia could be as little as 0.25 difference, however small differences such as this are of little or no significance when dispensing.

Anisometropia is only really significant when 
(a) the difference in refractive error is such that it produces unequal retinal image sizes (_aniseikonia_) that are 5% different in size. (this equates to 1.5% per dioptre difference) 
(b) the amount of differential prism induced in the vertical meridian when the px looks away from the OC exceeds 1 prism dioptre. (in particular with multifocals we need to consider a point approx 10mm below and 2mm in from the distance OC ie. the NVP).

When the retinal image sizes are 5% different or there is more than 1 prism dioptre differential in the vertical meridian (there is much more tolerance horizontally) you can be fairly certain that the patient will be unable to fuse the two images and hence will not achieve binocularity and will likely experience anisometropic amblyopia or diplopia.

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## drk

The sources I have used are:

1.) College lecture notes, not in print
2.) In John Amos' _Diagnosis and Management in Vision Care,_ Jimmy Bartlett's chapter "Anisometropia and Anisekonia" defines two levels of ansiometropia: 
"...(1) low, in which the anisometropia does not exceed 2.00 D, and (2) high, in which the anisometropia exceeds 2.00D." 

*So, in reality, I think I owe eyepod an apology! :shiner:* In fact, the 2D level is more of a clinical rule-of-thumb than a true defining criterion. 

Interesting note: only about 3-4&#37; of people have an anisometropia at the 1.5-2D or more level. 


Borish's _Clinical Refraction_ would be considered the "bible" on any refracting subject. I don't own a copy! It would be interesting what it says.

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## Diane

> The sources I have used are:
> 
> 1.) College lecture notes, not in print
> 2.) In John Amos' _Diagnosis and Management in Vision Care,_ Jimmy Bartlett's chapter "Anisometropia and Anisekonia" defines two levels of ansiometropia: 
> "...(1) low, in which the anisometropia does not exceed 2.00 D, and (2) high, in which the anisometropia exceeds 2.00D." 
> 
> *So, in reality, I think I owe eyepod an apology! :shiner:* In fact, the 2D level is more of a clinical rule-of-thumb than a true defining criterion. 
> 
> Interesting note: only about 3-4% of people have an anisometropia at the 1.5-2D or more level. 
> ...


 
I agree that, clinically, the 2 D level is pretty much commonplace.  I think, that I loaned that book out.  I though I had another one.  I'm going to look for it.  I'm not going to "loan" books out anymore.  

Bezza,

I believe that you added useful information as well.  I teach about the types of prescription imbalances, and would have discussed isometropia, anisometropia, and antimetropia as well.  You included the magnification/minification aniseikonia issues that go along with the prescription imbalances.  

Next we'll discuss how to correct image size with base curve, index of refraction, center thickness and vertex distance and the concerns with meridianal aniseikonia primarily due to refractive surgeries.  

Like I said, I love this topic.:)

Thanks,
Diane

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## orangezero

FYI

Clinical Refraction by Borish states "a difference between the refractive states of the two eyes that occurs in one or both principal meridians."

Thats the way I've always understood the definition.  So, +0.25DS OD and +0.50DS OS is technically anisometropia.  A 0.12DS difference would technically be as well.  

How many people aren't anisometropic??  How many people have optical problems due to the amount of their anisometropia?  Huge difference :)  I think a more reasonable application would be the amount  of anisometropia that leads to optical "issues."

For those interested, Clinical Refraction states it becomes clinically significant when 1D or greater, while System for Ophthalmic Dispensing (also by Borish) states 1.5D.

In a study quoted in Clinical Refraction, 20.2% were over 0.62D of aniso, 8.4% exceed 1D, 0.7% over 4D(!!!).

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## orangezero

and yes, I look in Borish on occasion, but it was handy as it was currently propping up my monitor a bit higher.  blasphemy perhaps...

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## Diane

> FYI
> 
> For those interested, Clinical Refraction states it becomes clinically significant when 1D or greater, while System for Ophthalmic Dispensing (also by Borish) states 1.5D.
> 
> In a study quoted in Clinical Refraction, 20.2% were over 0.62D of aniso, 8.4% exceed 1D, 0.7% over 4D(!!!).


1.5D was the clinical significance I found in System.... "I didn't loan it out."  Most eyecare professionals that I've been involved with have primarily used 2.00D imbalance as the clinical concern, however, some patients have issues with less than that.  It changes depending on the patient.  I've found over the years that any facial anatomy variances that places one eye higher than the other caused issues as well.  

I'm still loving this thread.:)

Diane

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## Scott R

I dont remember the formula, but surface labs can calculate the verticle prismatic difference in order to creat a "no line slaboff" with just about any progressive. I know essilor offers conventional slab off progressives in a number of different materials. I would imagine zeiss, hoya, rodenstock and others offer similar options.

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## chip anderson

Personally I think the idea of a pal for anisikonia is rediculous. 
However if you must try this, surely one of these genius individually computer generated places with digital surfacing should be able to do this for you in a heartbeat! If they can't the whole concept is a farce.

Chip

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## HarryChiling

I believe that in the case of Aniso, the freeform designs would allow for definate improvements over traditional progressives.  The free form lens can have the inset compensated based on the specific scenario, where the traditional lens will have the inset set in the lens and is in some cases compensated based on base curve (prescription range that will fit into that base) and/or add power (the amount of additional inset needed due to the add powers prismatic effect).  The problem with aniso (higher power anyway) is that generally when picking a base I will match both R and L lenses, however since the Rx is so different the Rx may call for different bases and if the bases are the same one of the eyes is going to recieve additional error.  That's my take on thigns what do you guys/gals think?

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## OPTIDONN

Sure I know that the potential is there but can or will the manufacturers of free form lenses generate them to certain specifications. Of course by using different placement of the addition etc. it will have an over all effect on design and blending and will lack symetry between the right and left lens. It could neutralize some of the prismatic effect but would these over all changes effect the performance?

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## HarryChiling

I don't know if they will or won't, but the potential is there.  The bases could be different between both eyes reduceing the difference in magnification without having to worry about the corridor being offset too much or too little for the patients Rx.  It's not even difficult when you break it down into what needs to be done.  I could almost definately say yes it is being done right now.  I would only really trust a freeform progressive that was solely on the back of the lens, this way the compensations don't have to account for any errors in the inset on the front part of the design plus the reduction in the keyhole effect is greatest in the back side desgins which would further help in this case.

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## OPTIDONN

Key hole effect is greatest in free form. Like looking through a key hole the closer it is to your eye the larger the field of view. I wouldn't be surprised if soon free form lenses get so advanced in their design incorporates correction for anisometropia. Doubt if any free form lenses available today would do much better than a traditional PAL for anisometropic patients. But the technology is there, designers just need to find away to incorporate this into existing designs. But with the reading addition higher, a consideration to neutralize some of the verical imbalance, than the other this could create a lens that may have "harder" design charachteristics than the other. I wonder if this unequal amount of surface astigmatism could cause a whole other set of problems. I'm sure that with extereme amounts, over 3.00 to 4.00 diopters, this lack of symetry could be pretty significant. Shouldn't be too far into the future that lens designers can significantly reduce this problem without the use of slab off.

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## Andrew Weiss

I'd love Darryl to get into this discussion.  My sense is that Zeiss already is doing much of this in their Individual lens; it'd be great to find out specifically how they handle Rxs such as the one I posted earlier in this thread.

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## drk

I think you're on to something, Harry, Andrew, and Donn.

Now, we have to be specific: which clinical problem are we talking about?
a.) prismatic imbalance induced by anisometropic Rxs or 
b.) anisekonia with isekonic lens design

With prismatic imbalance, there is no new territory to cover, here, I don't believe.

With isekonic lens design, then we get into a whole lotta fun.

As you know exhaustively, spectacle magnification is a combination of two phenomena: "power" magnification and "shape" magnification.

Of course the simplest and therefore most common option is to manipulater power magnification and deal with the resultant blur.

The more difficult task is to manipulate the variables in shape magnification: CT and BC.

-Manipulating CT only leads to physical/cosmetic drawbacks.

-Manipulating BC leads to optical drawbacks in SV and segmented MF by going off "corrected curve" 

-Manipulating BC in a progressive (as noted) leads to further optical/design drawbacks:
a.) Inset is varied based on base curve chosen. If one is prescribing a steeper base (which is usually the case), then the patient is getting less inset than necessary. 

b.) Very probably, there is a reduction in width of distance, intermediate, and near zone in the lens that has been fabricated with the "incorrectly steep" base curve. I'm assuming that a modern design will vary according to base curve (I'll call that _the Percepta Principle_).



So, how can individualized progressives help?
1.) I think by having overall wider near zones (if add has back surface component) and more precise design by prescription (atoricity on cylinder lenses).

2.) By being able to customize features, someday/now:
a.) Corridor length can be ordered "short"
b.) By applying the correct inset to match the near pd, modified by the appropriate prismatic power of the overall lens
c.) Probably by being able to match subtle design intricacies (Percepta Principle) to achieve the best match for the best binocular vision.



And, some day...gradient slab prism??????

Is this summary complete?

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## eyepod

> The sources I have used are:
> 
> 1.) College lecture notes, not in print
> 2.) In John Amos' _Diagnosis and Management in Vision Care,_ Jimmy Bartlett's chapter "Anisometropia and Anisekonia" defines two levels of ansiometropia: 
> "...(1) low, in which the anisometropia does not exceed 2.00 D, and (2) high, in which the anisometropia exceeds 2.00D." 
> 
> *So, in reality, I think I owe eyepod an apology! :shiner:* In fact, the 2D level is more of a clinical rule-of-thumb than a true defining criterion. 
> 
> Interesting note: only about 3-4% of people have an anisometropia at the 1.5-2D or more level. 
> ...


 
AWWWWWW, thanks, DRK!!

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## HarryChiling

Drk, sounds good. That is my greatest concern is the coridor placement when going off of manufacturers suggested base curves you run the risk of problems due to inset. I don't worry about the prism because like you've mentioned that area has been tread before and a slab can deal with any issues related to prism. The Zeiss Individual has variable inset and I believe others do as well, I know AWTECH with his Seiko Backside progressives can make the design just about anything you want so the Seiko lenses are also a great option. Just about any lens that's design is based upon the actual prescripiton (freeform) should do better than the traditional mono, multi or design by prescription series progressives. I say just about any (freeform), because I do see draw backs in using a design where the front surface has a progressive surface too it, because this surface is going to again have a set inset which will not be adequate, althogh they would still work better than the traditional lens due to low amounts of add powers on the front leading to wider widths throughout the lens, giving a little more leeway when it comes to corridor placement.

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## Metronome

Delete this post.

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## Optowoman

Don't know if this helps.  My husband is over the two diopter mark in difference and ALL he can wear is the GP Wide.  Could not adapt to Maui Jim (Image)   Even after changing B.C.  I can wear just about anything but he is the complete opposite.  His dist. is plus and as long as he fit high and in his beloved GP he is happy. Can't abide short corriders at all.  A bit disappointing as he is always my guinea pig for new lenses.  
 :Nerd:

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## bhess25

ok lab person at work here back up....when we surface any progressive lens we dont use a prism ring to move the OC for any compensation, this usualy results in (in some cases) extreme prism in the lens..ive seen a -4.00 @ as much as 4dbu..same with a +3.00 seen them with as much as 4.00dbd..its much easier to compensate any prism with a FT or RT than with a progressive..typicaly even if you try to use the prism ring while surfacing a progressive the end result is the same...if a person has a problem with anisomatropia and is experiencing "double vision" through the reading..really the only way to fix this is by fitting a FT and using slab off prism...ok its safe to return to the area now!

P.S. the "double vision" in the reading is usualy experienced when the difference in RX is at or above 3.0 diopters...this is when a reverse slab on the more minus comes into play.

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## tmorse

> ... the "double vision" in the reading is usualy experienced when the difference in RX is at or above 3.0 diopters...this is when a reverse slab on the more minus comes into play.


Regular slab-off  provides ^BU at the reading level, and if OD & OS are both minus, you slab the higher (or more) minus.

Reverse slab-off provides a ^BD, and is done to the *lower minus. ;)*

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## bhess25

> Regular slab-off provides ^BU at the reading level, and if OD & OS are both minus, you slab the higher (or more) minus.
> 
> Reverse slab-off provides a ^BD, and is done to the *lower minus. ;)*


right..i thought i was detailed enough...thanks for catching that.:cheers:

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## Win C

Hi everyone, I have a patient who has difficulty adapting to her new Rx.

R pl /-1.50 x120    VA 6/9+
L +3.50 /-1.25 x5  VA  6/6

Add for both eyes is +2.50 

Fitted her with XL transitions, previoulsly she was wearing Hoya GP.

The power difference for her previous RX was about 1.5D, but now it has increased to 3.5D. When she put on her new Rx , she felt uncomfortable and "giddy".

Prismatic difference measured thru the focimeter at the fitting height is about 1D BD. I put up a 1 prism BD in front of her right eye over her new progressve lens and she felt more comfortable for the distance. There is no  noticeble difference for near.

I am thinking for grinding 1D BD for her right lens. Is this the correct approach? Any advice?

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## bhess25

> Hi everyone, I have a patient who has difficulty adapting to her new Rx.
> 
> R pl /-1.50 x120 VA 6/9+
> L +3.50 /-1.25 x5 VA 6/6
> 
> Add for both eyes is +2.50 
> 
> Fitted her with XL transitions, previoulsly she was wearing Hoya GP.
> 
> ...


just taking a crack at this one (you might get a better response from one of the smarter people like harry, andrew or donn (not being a smart a**..i mean it)..being that the O.D. is a minus this would inherently have BU prism..and the O.S. being a plus would inherintly have BD prism...it might be easier to move the OC in the O.D. by grinding the prism there being that its the weaker Rx..to achieve the same effect in the O.S. being a +3.50 may lead to some thickness issues....my thoughts...1BD is a great idea in the O.D...what do the brains think?

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## Win C

> just taking a crack at this one (you might get a better response from one of the smarter people like harry, andrew or donn (not being a smart a**..i mean it)..being that the O.D. is a minus this would inherently have BU prism..and the O.S. being a plus would inherintly have BD prism...it might be easier to move the OC in the O.D. by grinding the prism there being that its the weaker Rx..to achieve the same effect in the O.S. being a +3.50 may lead to some thickness issues....my thoughts...1BD is a great idea in the O.D...what do the brains think?


By grinding 1 BD in the distance solves the distance problem. What about the reading? :o

In the past I did not even do any prism compensation for anisometropia as much as 4D and did not have any problem.

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## Win C

> I just dispensed a pair of Zeiss Individuals to a patient with the following Rx:
> 
> R: -1.25 -3.75 x 092, 1.0 prism down
> L: -6.75 -2.00 X 090, 1.0 prism up
> Add 2.50
> 
> She had been wearing progressives before with some difficulty. She put on the new ones and loved them immediately.
> 
> For years I relied on Rodenstock's Multigressiv II as my "go-to" lens for anesometropic patients who insisted on having progressives. Since it was discontinued, I've been using the Zeiss Individual and Individual Short with similar success.


those prism are usually ground in the distance part of the prescription? 

at the prism reference point, there is no prismatic difference. when the prism is ground in , will there be a prismatic difference in the prism ref point?

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## Just Optician

> Hi Eyepod,
> R -1.50
> L-0.75 
> Add+1.50 
> Patient used to have Vx.Physio, feel uncomfortable at intermediate?
> 
> By the way,could you guys tell me more about anisometropia patient which PALs more suitable for those patient with huge different power,One eye myopic, one hyperopic and with a lot of astigmatism
> 
> i mean which PALs suitable in which cases



I don't know what their previous rx was but in this prescription if the patient removed their glasses at the computer it would act as a monovision where the right eye would do the reading and the left eye would see the computer screen.  If you compare the width the patient is seeing with the naked eye to any progressive I would complain too about the intermediate.  Anisometropia is not the issue nor is it the type of progressive, (nor would a change in prism thining) ,it is a factor of the patient's present rx.   I would explain that their glasses offer good stereo vision where both eyes see at all distances but the intermediate zone will never be as wide as the naked eye.  When they reach a stronger add next time their prescription changes they'll probably work better.  

Just an opinion

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## bhess25

> By grinding 1 BD in the distance solves the distance problem. What about the reading? :o
> 
> In the past I did not even do any prism compensation for anisometropia as much as 4D and did not have any problem.


grinding the prism in would only comp. distance, with no effect on reading...the patients reading wouldnt change at all.
besides the patient isnt having any problems with the reading, with or without prism!

also some people can absorb prismatic differences in anisometropia better than others.I recently had to do a slab off for a patient that only had 1.00^ difference in Rx between eyes.

the Rx read like this

O.D. -1.50 -.50 X 180
O.S. +.50 _.50 X 13
Add +2.25

she experienced the usual diplopia with the reading card there were 2 #1's, one high one low.

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## bhess25

> those prism are usually ground in the distance part of the prescription? 
> 
> at the prism reference point, there is no prismatic difference. when the prism is ground in , will there be a prismatic difference in the prism ref point?


yes

and 

yes

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## rdcoach5

> I just dispensed a pair of Zeiss Individuals to a patient with the following Rx:
> 
> R: -1.25 -3.75 x 092, 1.0 prism down
> L: -6.75 -2.00 X 090, 1.0 prism up
> Add 2.50
> 
> She had been wearing progressives before with some difficulty. She put on the new ones and loved them immediately.
> 
> For years I relied on Rodenstock's Multigressiv II as my "go-to" lens for anesometropic patients who insisted on having progressives. Since it was discontinued, I've been using the Zeiss Individual and Individual Short with similar success.


You didn't mention if you used high index, but I think that's the only way the Individual is made.The higher the index the better . The Individual probably has the least peripheral distortion which undoubtedly helps. I would think that the Definity would also be a good choice.

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## Robert Martellaro

> Hi everyone, I have a patient who has difficulty adapting to her new Rx.
> 
> R pl /-1.50 x120 VA 6/9+
> L +3.50 /-1.25 x5 VA 6/6
> 
> Add for both eyes is +2.50 
> 
> Fitted her with XL transitions, previoulsly she was wearing Hoya GP.
> 
> ...


Maybe. This will eliminate VI on the distance gaze, but will increase the VI on the near gaze. Doing this without a slab might cause more harm than good. However, if you slab the lens, you'll need to compensate for the 1^ BD in right eye by increasing slab-off an extra 1^BU (assuming a custom slab on the right eye). If there is vertical prescribed prism, then add this to the prism that was used to eliminate the distance VI. The (adjusted) slab prism remains the same. (Note- the prescribed prism might not measure correctly at the PRP, but will read correctly at the FC and near vision point).

http://www.zeiss.de/4125680f0053a38d...256cfd002b9e3d

Another approach is to use a short corridor PAL that has a 2mm distance from the FC to the PRP. This minimizes VI on the distance, and also for the near VI by reducing the reading depth. Or, use a standard PAL for general purpose use, and readers for extended close tasks (I've found this to be best solution for most of my clients). If there is reduced VA due to pathology, I'd strongly consider segmented multifocals, especially if the add is above +2.75.

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## HarryChiling

I just recently had a patient with a Rx of:

-1.75 -0.50 x 175
+1.75 -0.50 x 180
Add +2.00

DPD = 29.5/30
NPD = 27.5/26

Interestingly enough the lenses were made using a progressive that had a 2.5mm inset now looking at the powers she would have less issues with ocular rotation in the right eye and more in the left eye if we factor the power and the prism into it.  This became evident when I took the NPD and DPD's seperately.  Her eyes roated 2mm in OD and 4mm in OS when viewing up close.  At first I ordered this job complete since she wanted AR, the lens came  back with a flatter base no doubt optimizd for the right eye.  She is having a hard time seeing out of the left though and is really having a problem with it.  I looked through my lens book and the ovation I believe has a 3.3mm inset, this makes it easier for the left eye and makes it so the right eye needs to work to get into the sweet spot.  I also chose to split the bases to optimize for each lens seperately.  I'll post when she picks them up and let you all know what went down.

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## TradeoffH8er

> This became evident when I took the NPD and DPD's seperately. Her eyes roated 2mm in OD and 4mm in OS when viewing up close.


Harry, what was the reading distance (lens to reading target) you used?  Also did you make sure that the reading distance was identical for both eyes?

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