Anisometropia PALs?

[stanley_tien]

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

[chip anderson]

Surely you jest!

[stanley_tien]

hi Chip,

I mean most suitable for anisometropia

[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.

[drk]

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

[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

[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.

[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:

[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.......................

[drk]

:):):):)

[Metronome]

Delete this post.

[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.

[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.

[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

[Bobie]

Free Form PALs is recommended for anisometropia.

[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.

[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?

[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.

[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% 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.

[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.


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.

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

[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(!!!).

[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...

[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

[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.

[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