Pt wears Poly w/ no aberration, Hi-index drives her crazy!

**ilanh** · 12-23-2005, 10:48 PM

I just had a mild myope who has been wearing CR39 and Poly for years. She has had no problems with either (although she says the CR39 is clearer). Rx is the same. We made her a 1.60, Shamir Piccolo lens with AR. The 1.60 was chosen because she picked a T-2 rimless frame (we could have used Poly). She came back complaining of horrible yellow lines in her vision. I thought it was the coating and had the AR removed. The chromatic aberration was still there. I am now pretty sure it is the 1.60.

My question: Is it common to have a patient who tolerates Poly but has chromatic aberration to 1.60?
-How can I be sure that the lens material that I received is hi-index? I can tell Poly by its sound; but I can't differentiate 1.60 from 1.67 or CR39. Note that we don't edge or cut any materials in my shop (last time I asked this question I didn't really get any serious answers).

Lastly, would it help to have some Poly, CR39, 1.67 blanks in the office so that we can put them up to the patient's eye and see which one causes chromatic aberration? (in cases where the pt has chromatic complaints).

I couldn't find Shamir Piccolo in trivex so I was thinking of doing it in Poly. However, to my surprise, the T-2 lab (Lensworks) said that they could do it in CR39 and that "we do it all the time". I suppose this is possible because they don't use screws but a proprietary bonding method.

**fjpod** · 12-24-2005, 07:59 AM

I don't have answers to all our questions, but consider the possibility that the aberrations noted with the hi-index could be coming from dislocation of the OC.

**karen** · 12-24-2005, 08:45 AM

Hi Dr H!
I have run into a few patients that can't wear 1.6. In most of the cases it was a BC issue put I suppose it could just be the material itself. It is strange that poly causes no problems but 1.6 does.

I don't know if having samples on hand would help to weed out the choromatic abberation people (I AM one of those people, most of us who are know it and tell who is dispensing us but it could be a newbie to poly) if you do it I suggest you do a pair mounted in a frame instead of just holding a lens up in front of the patient. The power and or base curve may make a difference so you may do this and the patient says no problem and then they pick up their Rx and it is a problem.

What's the center thickness of the lens? What's the RX? the CT may help you determine if it is 1.6.

Lastly, ask the lab if they warranty CR39 when they drill it. We'll drill it too but if it cracks c'est la vie...

**cinders831** · 12-24-2005, 10:13 AM

I have also noticed that some pts arent able to adapt to an aspheric design. Perhaps that is your trouble?

**GOS_Queen** · 12-24-2005, 10:18 AM

We encountered a similar situation with one of the OD's that work next to our store.

She has a very mild Rx, has worn poly a/r for years successfully. We put her in 1.67 a/r for her new pair. When she came to pick the new pair up, she couldn't get off the dispensing chair the new lenses made her so nauseous !! We did remake it to "match base curves" but that still made her nauseous (but not to the extreme). We ended up putting her back in poly and she is happy as a clam:bbg:

(note: she just wanted to "try" the new material)

Karen :hammer:

**OPTIDONN** · 12-24-2005, 02:04 PM

If she is only seeing yellow it may not be chromatic aberration. I know that some high index materials have a bit of a yellow color (I am not sure if the Shamir lens does though). It could be the concentric circles caused by the polished edges and given a yellow color from the high index material. It would be hard to tell without seeing the glasses.

**Matthew** · 12-24-2005, 02:32 PM

Image comes in Trivex.

One thing to look for, in her old lenses....Is there prism thinning?

Some labs will typically put about 2 units on a 2.00 add.

If old lenses do not have prism thinning and new ones do that may account for the yellow.

If you look through any hi index or poly you will notice that looking extreme right through the blank will make things have a yellow shadow and to exteme left a blue shadow.

There is something optics related in the way that lens is made that gives it that shadow.

Definatley the OCs and or prism thinning can do that.

**ilanh** · 12-24-2005, 03:41 PM

Interesting responses. I was almost sure by now that this was a chromatic aberration issue related to the lens material. The OC is not an issue since we marked both PD's and the OC's were identical. My understanding of base curve issues is that it could cause perceptual discomfort but not chromatic aberration (I did not compare base curves). With regard to prism thinning I have to confess that I did not even remotely consider that as a possibility? Does anyone else think this could cause chromatic aberration? From an optical/physics point of view it would make sense.

Ilan

P.S: Does anyone know what is VSP policy regarding patients who need multiple redo's? This is the third time she's sending this back.

**Darryl Meister** · 12-24-2005, 05:59 PM

Chromatic aberration (or at least "color fringing") will vary based upon either the Abbe value of the material or the amount of prism present (Chromatism = Prism / Abbe). Keep in mind that 1.6 High-index lens materials all have higher Abbe values than Polycarbonate, so increased chromatic aberration could only be due to the amount of prism involved. This could be due to the pupil positions above the optical centers, prescribed prism (including prism-thinning), longer vertex distances, larger frame sizes, and so on. While the choice of base curve won't increase chromatic aberration, it can make the wearer more susceptible to its effects in some cases. I have a course on chromatic aberration at OptiCampus - Chromatic Aberration Course, which you may find useful.

**spartus** · 12-24-2005, 06:36 PM

Originally Posted by ilanh

P.S: Does anyone know what is VSP policy regarding patients who need multiple redo's? This is the third time she's sending this back.

If memory serves, I think VSP gives you one redo within 90 days.

**Darryl Meister** · 12-24-2005, 07:41 PM

Is she wearing progressive lenses for the first time?

**QDO1** · 12-25-2005, 05:15 AM

whats the prescription please?

**karen** · 12-25-2005, 12:08 PM

Originally Posted by ilanh

P.S: Does anyone know what is VSP policy regarding patients who need multiple redo's? This is the third time she's sending this back.

Depends on the lab. VSP makes us do 1 redo for up to 6 months no charge. By this time you will probably fall back on whatever the labs regular redo policy is for a third time redo. Your Shamir rep's name is Vanessa (I think-or it's Anthony) call them and ask for a coupon if you end up doing it in the Shamir again, can't hurt to ask. Then neither you or the lab has to pay...

**Andrew Weiss** · 12-27-2005, 11:24 AM

Originally Posted by ilanh

Does anyone know what is VSP policy regarding patients who need multiple redo's? This is the third time she's sending this back.

VSP's requirement on free redos is one time within the first 6 months, and only if there's a defect in the lens, in fabrication, in the Rx or in fitting measurements, or a non-adapt problem. I have yet to find a VSP-authorized lab that will do multiple free-redos on VSP jobs, for the (very good) reason that VSP cuts their profit margin to the bone, just as they do with dispensers.

(PS: The VSP labs I know will also honor scratch-warrantee and AR-warrantee redos, usually one free redo within one year for scratch-warrantee and whatever redos are required for AR-coating failure for however long the AR provider warrantees it.)

**QDO1** · 12-27-2005, 01:29 PM

Originally Posted by ilanh

I just had a mild myope who has been wearing CR39 and Poly for years.

big jump between CR39 and poly, small jump between poly and 1.6

Originally Posted by ilanh

I am now pretty sure it is the 1.60.

are you sure the old ones ARE poly

Originally Posted by ilanh

I couldn't find Shamir Piccolo in trivex so I was thinking of doing it in Poly. However, to my surprise, the T-2 lab (Lensworks) said that they could do it in CR39 and that "we do it all the time". I suppose this is possible because they don't use screws but a proprietary bonding method.

Your lab "changes them all of the time"???

Are you very certain you know exactly what materials are in each job??

**Metronome** · 02-15-2008, 12:32 AM

Delete this post.

**Judy Canty** · 02-15-2008, 02:07 PM

Caution...2+ year old thread!

**jediron1** · 02-15-2008, 02:18 PM

Originally Posted by karen

Hi Dr H!
The power and or base curve may make a difference so you may do this and the patient says no problem and then they pick up their Rx and it is a problem.

What's the center thickness of the lens? What's the RX? the CT may help you determine if it is 1.6.

Lastly, ask the lab if they warranty CR39 when they drill it. We'll drill it too but if it cracks c'est la vie...

I agree with everthing said. I would double check the oc right to left or what ever your strongest lens is then check the other. I know that's basic optics but you would be surprised at how many oc's that I have found that are way off especially in stronger lenses and 1.60.

just my 2 cents

**FVCCHRIS** · 02-15-2008, 05:05 PM

Originally Posted by Judy Canty

Caution...2+ year old thread!

I love it! Thanks Judy for pointing that out. Do you think they ever solved the problem??:hammer:

Leftover Pot roast is a good thing, maybe not 2 years though!

**Judy Canty** · 02-15-2008, 10:17 PM

I sure hope so. The warranty has probably expired. ;)

**Happylady** · 02-16-2008, 06:47 PM

Why are all these old threads being revieved?

**jediron1** · 02-17-2008, 10:30 AM

Originally Posted by FVCCHRIS

I love it! Thanks Judy for pointing that out. Do you think they ever solved the problem??:hammer:

Leftover Pot roast is a good thing, maybe not 2 years though!

Left over spaghetti fried in butter is great too but not after two years. Just a thought! ;)

**jediron1** · 02-17-2008, 10:34 AM

[quote=FVCCHRIS;229003]I love it! Thanks Judy for pointing that out. Do you think they ever solved the problem??:hammer:

Ya but they may still have the same problem. 2 years hummmmmmmmmmm
maybe not. But inquisitive minds would like to know.