Difference in RX OU

[Now I See]

Hi everybody!
I have a patient that has come in with a new pr of glasses:
OD +5.25 -0.50 x 143
OS +7.25 sph pd= 55
Frame A:49 B:26 ED:50 DBL:18 full metal
Lens material: Asph Poly


The pair I made for her last year was:
OD +4.50 -0.50 x 157
OS +6.00 sph pd= 26.0 ou
Frame A:47 B:24 ED:48 DBL:18
Lens Material: Asph Poly

**The problem she is having is that her left lens in the new pair makes her left eye look so much bigger than her right eye. It didn't seem as noticeable in the pair from last year. My question is this...is there a way to solve that problem? I know the RX is playing a role here, but I'm wondering if there is something else I can do? Would a thinner lens help? A different material lens? A digital SV lens? The patient is 11, she wears contacts, but would like to wear her glasses from time to time, but is very self-conscious about the difference in the appearance of her eyes w/ the glasses on.

Any help would be appreciated!

[optical24/7]

Reduce the vertex using a plastic, rather than metal frame. (you didn't mention if she's going from plastic to metal). Make sure the OS especially is thin as possible.

I understand she's 11,(poly) but an Rx this high needs better abbe's for vision. Sometimes poly isn't the best choice even for a child. A 1.70 would give her that (better vision) plus a thinner lens reducing the magnification even more.

[mdeimler]

Were the lenses surfaced or finished blanks ? BC may also be higher on new glasses. 1.67 usually fits the bill nicely.

[Wes]

A slightly flatter curve would reduce the magnification as well, but this would increase off axis aberrations. An aspheric 1.70 would work wonders, but it's not cheap.
decisions, decisions.
Also, that's a lot of decentration. My rule of thumb is: anything over 5 mm means your frame is probably too big anyway; in higher powers, anything over 2.5 mm is too much.

[mdeimler]

Also, that's a lot of decentration. My rule of thumb is: anything over 5 mm means your frame is probably too big anyway; in higher powers, anything over 2.5 mm is too much.

Good point. Decentration is the killer.

[chip anderson]

How or why did her PD change? Use different index for different eyes, will help reduce magnification, don't use poly on anything with this much plus. You might (or you might get in trouble with non-aspheric O.D. and aspheric O.S. Aspherics reduce maginfication O.S.

Chip

[Wes]

Hi everybody!
I have a patient that has come in with a new pr of glasses:
OD +5.25 -0.50 x 143
OS +7.25 sph pd= 55
Frame A:49 B:26 ED:50 DBL:18 full metal
Lens material: Asph Poly


The pair I made for her last year was:
OD +4.50 -0.50 x 157
OS +6.00 sph pd= 26.0 ou
Frame A:47 B:24 ED:48 DBL:18
Lens Material: Asph Poly

**The problem she is having is that her left lens in the new pair makes her left eye look so much bigger than her right eye. It didn't seem as noticeable in the pair from last year. My question is this...is there a way to solve that problem? I know the RX is playing a role here, but I'm wondering if there is something else I can do? Would a thinner lens help? A different material lens? A digital SV lens? The patient is 11, she wears contacts, but would like to wear her glasses from time to time, but is very self-conscious about the difference in the appearance of her eyes w/ the glasses on.

Any help would be appreciated!

How or why did her PD change?
Chip

Children grow up.

[Now I See]

Reduce the vertex using a plastic, rather than metal frame. (you didn't mention if she's going from plastic to metal)....

Both metal frames.

Were the lenses surfaced or finished blanks ? BC may also be higher on new glasses. 1.67 usually fits the bill nicely.

The pair I made last year were surfaced, the current pair, she got from her doctor's office.

A slightly flatter curve would reduce the magnification as well, but this would increase off axis aberrations. An aspheric 1.70 would work wonders, but it's not cheap.
decisions, decisions.
Also, that's a lot of decentration. My rule of thumb is: anything over 5 mm means your frame is probably too big anyway; in higher powers, anything over 2.5 mm is too much.

Thank you...this does present a challenge, because her eyes are a little close set.

How or why did her PD change? ......

Chip

The old pd was taken at my office last year, so that's the pd I read w/ the pupilometer. The new pair were made at her doctor's office, that's the pd I got when I read the new lenses. She's 11, and she has done some growing over the last year.

The patient and her family have been a friends of our family for years, I didn't have a frame that she (the pt) liked, and she found one at her doctor's office. The doc's office put her in Trivex to begin with (can anyone say THICKNESS???) Then they put her into Aspheric Poly, but there is this issue with the larger eye appearance, that wasn't as noticeable with the old RX. So, they were thinking of getting the lenses made at my office, but I didn't want to move forward without feeling confident that I can offer a solution to the problem. I'm all ears for more suggestions, but what I'm hearing so far is...
1. Changing the material
2. Using a flatter BC
3. Less decentration

Do you think a combination of all of these things would make a noticeable difference?

[CCGREEN]

Also, that's a lot of decentration. My rule of thumb is: anything over 5 mm means your frame is probably too big anyway; in higher powers, anything over 2.5 mm is too much.[/QUOTE]

oh yes 6mm of decentration for each eye with that strong of a power is not just to much...its WAY to much. It makes a huge difference in lens thickness. I find that it makes much much more difference then what most people relize. To much decentration will increase nasel thickness on plus lenses thus increasing magnafication.

[Wes]

@ Now I See: Absolutely.

[AngeHamm]

Good for you for being so focused on both how she sees and how she looks. I wish there had been more attention paid to the cosmetics of glasses when I was 11 and getting them.

[Jubilee]

Its always hard to balance out the optics vs the cosmetics on scripts like this. IF digital is not an option, then I would look into matching the base curves of the previous pair, or if possible, use a flatter bc on the OS.

I love the 1.70 idea as well, and have been very impressed with both the cosmetics and clarity with it. This would be my first choice.

[wearegood]

Its always hard to balance out the optics vs the cosmetics on scripts like this. IF digital is not an option, then I would look into matching the base curves of the previous pair, or if possible, use a flatter bc on the OS.

I love the 1.70 idea as well, and have been very impressed with both the cosmetics and clarity with it. This would be my first choice.

Then the problem of thickness will arise.

[Wes]

Then the problem of thickness will arise.

1.70 will be much thinner than poly.
All other things equal, in a plus lens a flatter curve will produce a thinner lens, and aspherics are thinner than traditional spherical lenses.

[Robert Martellaro]

**The problem she is having is that her left lens in the new pair makes her left eye look so much bigger than her right eye. It didn't seem as noticeable in the pair from last year.

Determine if the vertex distance has increased with the new eyeglasses- an increase in vertex distance will not only increase magnification, it will increase the difference in magnification between the eyes, and aggravate the increase in differential magnification due to the Rx change.

but is very self-conscious about the difference in the appearance of her eyes w/ the glasses on.

To decrease the differential magnification, we need to increase the magnification in the right eye. This is done by increasing the base curve (match the left eye for the best cosmetics), and by increasing its thickness.

http://www.opticampus.com/tools/magnification.php

If you are able to match (or decrease) the vertex distance of the old eyeglasses, matching the thickness and BC of the left lens might be enough to duplicate the appearance of her old eyeglasses, depending on the BC and CTs of the old and new lenses. If not, you will need to increase the right eye thickness by 1mm to 4mm thicker than the left eye. Consider using a zyl frame to hide the nasal thickness, a somewhat round shape, and nose pads to help position the 180 line close to the pupils.

[Barry Santini]

Changing BCs by steepening the left is good, but must be done in a good FF lens design that allows BC's to be specified. I would use 1.60 index for best vision, or even better CR 39 if you follow Robert's excellent frame shape/size suggestions.

In CR 39, I would try an 8.75 base OU. and watch that vertex fitting distance.

Also, consider dropping the AR, using using one with more reflectance, such as Zeiss SET Gold. This will hide/distract from the magnified-eye appearance
.

Heck, I've done CR-39 +9.25s in a Silhouette Titan Minimal Art with knife edges and drilled the temporal attachment in by an add'l mm. A round/oval shape, fitted with minimal decentration in a rimless with SET will DO the trick!

B

[Now I See]

Thanks, so much to all!!! I knew this was the right place to ask questions! You guys (and gals) put the "I-C" in optics!

I'm going to talk to her mom and see what we can do...it's a learning experience for us both, so I'll keep you posted and let you know what we come up with!

[sharpstick777]

Even though I am a fan of FF, none of the usual names offer good Anesekonic compensations or options. Ansekonic lenses can be designed by adjusting the power in one, and then the base curve in the other.

There is a good calculator on Opticampus to determine both numbers with a degree of certainty.

Right now, Shaw Lens (Peter Shaw is on Optiboard) has the only lenses that compensate digitally.

[Darryl Meister]

The problem she is having is that her left lens in the new pair makes her left eye look so much bigger than her right eye

Even though I am a fan of FF, none of the usual names offer good Anesekonic compensations or options... Right now, Shaw Lens (Peter Shaw is on Optiboard) has the only lenses that compensate digitally

If I recall, Dr. Shaw is attempting to compensate for dynamic anseikonia. This would not eliminate magnification differences between her right and left lenses. In fact, it could potentially make them just as bad, but reversed, so that her right eye looks bigger than her left, which would not really address the patient's chief complaint regarding cosmetics.

Best regards,
Darryl

[Dave E]

not sure if this would help may be some could let me no but could atoric design in one eye and aspherics in the other would that help with one eye looking bigger than the other .

[Peter J Shaw OD]

Hi all, Van Rue mentioned this thread, I met him on ODs on facebook , SHAW lens addresses both dynamic and static inter-ocular magnification differences. The appearance of the eyes would be equal with our lenses for the above patient. We use a digital back surface design , they would not look worse at all since our method will use a flatter aspheric in the stronger plus eye and a higher shape factor in the less plus eye, the software algorithm is carefully constructed not to create a static magnification reversal. In this case the optimum curves would be to make the higher plus eye appear a little smaller compared to a "standard" lens and the lower plus eye to appear a little larger so that the end result is equality. I hope that this clears up any lack of clarity.

[optical24/7]

Magnification is caused/induced by power, material, index, thickness, vertex along with lens size and decentration ( the last two both relate to thickness). Asphericity potentially could or could not influence magnification by thickness*. ( Atoric, not this Rx.)

To control or reduce magnification as much as possible, you need to address all of the above. The two variables that will mean the most are thickness and vertex on any Rx. Controlling thickness starts with lens size and PD ( As small and round/oval as possible and FPD as close as possible to patient's PD). Material (index) will make a difference because higher index's uses (require) flatter curves reducing the thickness (and vertex). (Be aware that not all hi-indexes have great abbe values. With high powers like the above, you need to start thinking of LCA's and their affect on their vision). Using a frame that sits as close as possible to their eye reduces the vertex distance.

* As far a aspheric/atoric helping. Depends. If you're talking using corrective curve deviation that we traditionally think of with aspheric/atorics, no. A +/-.50 cyl would have an extremely small amount of "curve deviation" for the cyl. The smaller the lens, the less curve deviation or asphericity is required. This is a 49 eye size so little deviation is induced. I don't think just asphericity ( or atoricity) in this small of eye size would reduce thickness much.

Now then, if you were to do a radical aspheric design like IceTech ( I don't work for them) makes then you could reduce the thickness even more. ( by radical asphericity I mean a radical curve deviation to remove lens material, not a corrective curve deviation. Think SuperModular lenses (ok, I'm old and remember those..)

I'm sure someone will add or correct me on the above.

[Darryl Meister]

SHAW lens addresses both dynamic and static inter-ocular magnification differences.

Peter, Can you elaborate on this point? Are you stating that you are correcting static and dynamic aniseikonia, simultaneously? (I can't see how this could work, at least without introducing a great deal of spherical aberration or something.)

Best regards,
Darryl

[Peter J Shaw OD]

Peter, Can you elaborate on this point? Are you stating that you are correcting static and dynamic aniseikonia, simultaneously? (I can't see how this could work, at least without introducing a great deal of spherical aberration or something.)

Best regards,
Darryl

Hi Darryl, and thanks for the question,
I haven't been on optiboard for a while, its been a crazy 6 months since we launched at VE in NY.
Image size is calculated using the corneal vertex distance (well really the true vertex distance which is posterior to the corneal apex, the entrance pupil) this coincides approximately from a cosmetic standpoint at the iris, and the corneal limbus. these structures will appear the same size in each fellow eye with an isogonal lens system). A side benefit is reduced dynamic magnification, now there are many discrete solutions for an isogonal lens system, our (international patent pending) proprietary iterative computer design chooses the optimum combination of base, index, thickness, geometry, asphericity and index to subsequently correct the dynamic magnification (ie prismatic effect) while maintaining an isogonal correcting system. It is rather complicated but that's the beauty of computerized design. Digital surfacing corrects any spherical aberration is fully controlled by our atoric/aspheric backside surfacing even with front side aspheric lenses. We have had great success and our most surprising successes have been patients with small distance Rxs (plano to -1.00) in a PAL with small degrees of anisometropia (0.25D to 2.00D). Spherical aberration is not an issue at all, and our lenses have less barrel and pincushion effect than typical FF lenses (also less pincushion equals less spherical aberration).

[Peter J Shaw OD]

Magnification is caused/induced by power, material, index, thickness, vertex along with lens size and decentration ( the last two both relate to thickness). Asphericity potentially could or could not influence magnification by thickness*. ( Atoric, not this Rx.)

To control or reduce magnification as much as possible, you need to address all of the above. The two variables that will mean the most are thickness and vertex on any Rx. Controlling thickness starts with lens size and PD ( As small and round/oval as possible and FPD as close as possible to patient's PD). Material (index) will make a difference because higher index's uses (require) flatter curves reducing the thickness (and vertex). (Be aware that not all hi-indexes have great abbe values. With high powers like the above, you need to start thinking of LCA's and their affect on their vision). Using a frame that sits as close as possible to their eye reduces the vertex distance.

* As far a aspheric/atoric helping. Depends. If you're talking using corrective curve deviation that we traditionally think of with aspheric/atorics, no. A +/-.50 cyl would have an extremely small amount of "curve deviation" for the cyl. The smaller the lens, the less curve deviation or asphericity is required. This is a 49 eye size so little deviation is induced. I don't think just asphericity ( or atoricity) in this small of eye size would reduce thickness much.

Now then, if you were to do a radical aspheric design like IceTech ( I don't work for them) makes then you could reduce the thickness even more. ( by radical asphericity I mean a radical curve deviation to remove lens material, not a corrective curve deviation. Think SuperModular lenses (ok, I'm old and remember those..)

I'm sure someone will add or correct me on the above.

yes, yes, yes, yes, yes all correct,