Prejudice against poly--totally unfounded!!!

[Jim G]

I just read the notes posted to "PLEASE HELP ME :(" and I feel compelled to reply.

Maybe I'll be accused of getting on my soapbox but, the PREJUDICE out there against poly is appalling. Yes, prejudice! Webster: "A strong feeling about some subject, formed UNFAIRLY or BEFORE ONE KNOWS THE FACTS." (Caps mine.)

I don't mean to talk down to you professionals but some of the comments made have to be traced to a complete lack of knowledge of optics.

Some background on poly. Back in the 80's, poly had significant peripheral aberrations. However, these were caused by primative manufacturing methods that resulted in "wavy" front surfaces. Q.C. standards often established a 25 or 30 mm spherical aperature for clear vision allowing for "junk" surfaces outside that aparture. This fact, misinterpreted as chromatic aberration, gave poly it's bad name. Today's manufacturing methods have mostly eliminated this problem leaving us with real optics as an issue.

All powered lens systems have some degree of distortion away from the optical center of the lens. Remember the 6 common aberrations in any lens system? 1) Chromatic aberration--lateral & axial; 2) Spherical aberration--longitudinal and transverse; 3) Coma; 4) Marginal or Oblique astigmatism; 5) Curvature of field; and, 6) Distortion.

Corrected curve designs address spherical aberrations and marginal astigmatism. The other factors either are of limited effect or not capable of correction by lens design. (Don't get me off on base curves here; dispensers who try to maintain a base curve as the correction progresses are going against all that we've learned in optical physics.)

Chromatic aberration IS PRESENT IN EVERY POWERED LENS. Transverse Chromatic Aberration is calculated as follows (Longitudinal Chromatic Aberration is not a factor): TCA = (Lens Power x Deentration)/Abbe Number. The operative is at what point does it affect normal sight. Obviously, the lower the abbe number, the closer to the optical center this LINEAR progression of aberration will be noticeable.

Multiple studies have shown that patients will move their heads at between 20 (80%) and 30 degrees (100%) of viewing away from the center of the lens (Angle of Gaze). At a vertex distance of about 10 mm, 2 degrees are about equal to 1 mm. Taking the above, 30 degrees would be about 15 mm's off center.

With some degree of certainty, we can therefore use the 30 degree angle of gaze as the point to measure where an aberration would become bothersome to a patient.

Using a -5.00 powered lens (which encompasses over 94% of myopes), at a gaze angle of 30 degrees, the Snellen Notation for different materials is as follows:

CR-39 = 20/26
Poly = 20/31
1.60 plastic = 20/29
1.66 plastic = 20/31

And yet some of you will insist that 1.60 and 1.66 work where poly won't. For comparison, a 0.25 diopter power error equates to 20/27. I would challange any refractionist to refract within that error 10 times in a row on the same patient at the same time of day let alone the differences between morning and evening! IT JUST AIN'T AN ISSUE FOLKS. GET OVER IT!

Sure, CR-39 and glass edhibit less aberrations. Why then should we even consider poly?
o Poly is unequivically today's best value in lenses.
o Poly gives patients what they are looking for...lightness and thinness, at a fair price.
o Built in UV attenuation.
o Unequaled protection.
o Poly's "inferior" optics (similar to 1.6 or 1.66 but "worse" that CR-39) ARE NOT A FACTOR UNTIL THE POWER EXCEEDS -4.00 OR -5.00 DIOPTERS. Further, at these and higher powers, the loss of acuity is LESS than that for marginal astigmatism or power error.

For higher powers, aspheric/atoric designs become attractive. The Vizio, from SOLA, is a poly option as are 1.60 & 1.66 products from Optima, Pentax and SOLA's Vizio 1.66.

You can do a couple things when dispensing (any high index material) to minimize power errors. Ensure that placement of the lens relative to your panto angle is correct to ensure that the optical center and visual axis intersect. Because lenses with smaller corneal vertex distance have lesser decentration for the same angle of gaze, fit the lenses as close as anatomically possible. Stick to the manufacturers (or DVI's) recommended base curve to minimize accentuating the aberration.

Lastly, some seem to believe that an AR coating will reduce chromatic aberration. While I am a strong proponent of AR, it will have absolutely no effect on chromatic aberrations. That's optics folks.

I'll further the debate by throwing out that the independent opticians survival is based upon using your knowledge (not prejudice) to recommend the optimal combination of a lens system with consumer needs to satisfy that patient.

By the way, I have a Thin & Dark PAL, 1.50 C.T., Rx (-3.25, -2.50 +2.25) in a small frame and it's very comfortable, affords "superior" optics and is the optimal base for an AR coating! How many of you would consider giving a patient this option. Could a prejudice also exist against glass?

There, I said it!!! And, I have my gloves on.

[hcjilson]

I've got to say I'm with Jim on this one...and thats coming from one whose earlier predudice was based on nothing more than having to use a different wheel when edging them :).Last year I was comp'd a pair of Gradal's in poly and can honestly say I couldn't see any difference between them and CR39 Monomer.All this talk of Abbe values is BS.My customers don't usually have spectrometers, lensometers, or lens clocks with them.How can those of us so concerned about abberation sell progressive lenses?? Poly is here to stay! When so much of our time is taken up by solving customer's problems (the majority of which deal with uncomfortable spectacles) why do we insist on biting the hand that offers the customer some satisfaction?

To digress...Jim, did I read that you were with Walman? If so is my friend Connie Lewis still there? If so tell him "Hey" from Harry Jilson.
Tx

------------------
Harry J

[This message has been edited by hcjilson (edited 04-05-2001).]

[Judy Canty]

I'm with you guys on this one, also. I use a great deal of poly and I haven't had any fallout from patients.
I knew Connie also, back in his Hilbert days in Norfolk, VA. Great guy!

[pedseye]

Hey Jim,

1st let me say...ya, you betcha! If you've read my take on this, you'll see I have never been afraid of poly and never had any problems with it...Ya know. I've dispensed poly in powers as high as they could be made with NO problems. Very soon I will be dispensing to a majority of children and I am glad to hear of the success you are still having with poly. What's YOUR favorite poly manufacturer, eh? If ya haven't figured it out yet, I used to live in Plymouth and worked in Minnetonka. My husband is from up north...Brainerd lakes area. Nisswa.

[Texas Ranger]

Jim G, never fear to speak the truth. must say that we were weened on glass, was around when "plastic" came into the market. my boss then wouldn't sell it! over the years it's gotten better, but so has poly. we use lots more of now that we edge it in-house, realized that it was really an in-house edging issue before, now we send out glass work. my next lenses are to be the panamic in 1.6 glass photo-bronze with a zeiss ar. looking forward to it. wear airwear panamic crizal's now, just love em'. Al.

[JRS]

Very good post Jim G. So on the money. Poly, and for that matter, CR-39 are not the same as when I first started (35 years ago). The improvements are fantastic.

I was really tickled by the poster on the other thread who said "wholesalers on DVI are messing up base curves". Talk about guess work....

[Joann Raytar]

I have worn poly polarized lenses in my sunglasses for a couple of years now and don't see much of a difference from plastic except they are much lighter.

In my dress glasses I still prefer plastic. Poly was good during the day but at night I was seeing halos around street lights, etc. I wasn't looking for them; I just picked them up. I know that if I were to wear them more often my brain would get over it.

In my own experience I may have had one person who I felt I needed to switch out of poly due to adaptation issues and one other who changed jobs and ruined his lenses with acetone. Personally, if I were in a position to get that much acetone splashed in my face on a daily basis I would be wearing safety shields anyway. During the days of my youth I had a bag pressurized bag of alcohol blow up all over me and that was no fun (when the directions on the surface coater say turn off the compressed gas tanks, they mean it); I can't imagine getting acetone sprayed all over yourself.

Now, I have also seen poly save a few folks from injury. Actually the lenses fared much better than the frames. A customer of mine was working on his car engine with a hooded sweatshirt on, hood down. He leaned over to do something and the hood got caught in the belt. He was pulled face first into the engine. He ended up with several stitches from the bridge of his nose up his forehead and had a broken nose. The frame was seriously bent and one of the lenses ended up with a decent gouge but there was no damage to his eyes. Also say a special on the learning channel. A golfer took one in the eye after it bounced off a tree. He was wearing PGX. The ball drove shards of glass as far back as the macula. Poly wins for safety in the case of freak around the home accidents.

[This message has been edited by Jo (edited 04-05-2001).]

[This message has been edited by Jo (edited 04-05-2001).]

[Alan W]

Jim G
Your posting is impressive.
Your logic is impeccable.
Your knowledge is beyond dispute.
Now, you go tell that to the truckers that come storming into my dispensary and watch how they make minced meat out of you when they see the edges of objects unclear, tree lines that are yellow to brown, and the edges of the white lines on some roads edged with a slight blue.
You tell them thar dumb stupid truckers that according to your logic they are wrong.
You are presenting an impeccable argument full of theory. I used to be just like that. But, I have changed my viewpoint (you'll excuse the expression!) and I listen to my patients and not the slide rule. I, in my old age, with limited knowledge, have suddenly become very real world. And, you wann know something?
I sold them the polys for all the right reasons . . . just like you. But, if you'll excuse me and my apologies to a dear colleague named Joe Bruneni, who put poly on our plates, . . . if my patients tell me they see better when I move them over to Hi-X or whatever, I am happy, they are happy, and THAT is the base curve that makes the difference.

PS the number of poly rejects is very small, but real and there. You need to get a hold of yourself and put things in their right context. Some people can't take Cardizem and others can take Procardia XL. Both are there for the same reason. Some people see blue when they take Viagra. Others don't. So, don't be so positive your theory is fullproof.
Now I need to take my prune juice and Geritol!

[PBS]

JimG,
I don't use poly very much. Only for safety issues and if someone actually asks for it. I just don't like the way it looks, feels, and sounds. It dents and I've seen more poly lenses look like crap after a year than any hi index. They just don't seem to take abuse very well. And....as we all know, they're harder to shape and I don't like my wheel clogged. They're messy and well.... listen to me.... I guess I'm just thinking about myself. But then again, I don't think I'm hurting any patient by offering hi index over poly. That's that, and that's the way it'll always be. Poly just has a cheapness about it that turns me off. Period!!

[Alan W]

Oh, BTW, JimG . . .
Re:
"I don't mean to talk down to you professionals but some of the comments made have to be traced to a complete lack of knowledge of optics. "

You did, it doesn't, and don't ever insult your colleagues again, especially the ones who use Walman Optical, and the ones who use Walman Optical who could give you a bath in optics! That sucks!

[Pete Hanlin]

I've been a poly fan for quite some time- its nice to see from the responses here that we're in good company. I do find that some otherwise great Opticians/ODs do seem to have a grudge against the material, however. One OD I work with swears he gets about a 50% reject rate- which he attributes to the "internal stress" of the lens. He is fond of pointing out the stress pattern you see in poly when viewed through a polarizing filter. I pointed out that heat treated glass lenses have a very distinct cross pattern, and that doesn't seem to disturb patients.

The only time I'm wary of using poly is when it is surfaced. Poly is very sensitive to heat during the generating/fining/polishing process, and I prefer poly products which are cast.

Good points, Jim. The RVA values you referred to are part of a CEC I'm presenting in Ft. Walton Beach tomorrow. Having been a -4.75 at one time, I found poly worked just fine for me (though I did enjoy the pretty blue fringe it would put on the purple flowers in front of our office ;) ).

Pete

[lguess]

Leaving all the arguments about abbe values, etc. I've got to tell you guys a story: I was at Vision Expo East and staying at a funky hotel in lower Manhattan. I figured out the bus routes and took buses to and from the show at Javits Center. I had just returned to W. 34th St at 5th Avenue on a bus when one of NYC's famous potholes got me. I went down, my glasses cut a couple of nasty gashes in my right eyebrow and forehead. I bled like a stuck pig, and somehow or other staggered back to our hotel (New Yorkers, of course, didn't even notice this CA guy walking along bleeding like crazy). After cleaning up the wound I realized that my eyeglasses just needed some adjusting (of course I had pliers in my toilet kit!). Let's hear it for a titanium frame and poly lenses: If I would have had glass or even CR39 lenses my injury would have been a lot worse. I'm definitely a poly wearer from here on out. BTW, my wife says my new scars make me very rakish looking, and she'll love me anyhow-

Larry

[chip anderson]

Have any blind test been run where the patients were: Given 3 pairs of glasses in the same Rx's, the same frames with the same centers, etc. except the lenses were made of : 1 Glass, 2 CR-39 3 Polycarbonate. Then had the patient's use these in real life situations and asked which did you seem to see the best??

Would be most interested in the results if not paid for by the winner.

Chip

[Corey Nicholls]

Hi Guys,

I personally think that poly like any other material, have their place.

I remember when I first started, the old optom I worked for didn't trust CR39! Mind you this same old fella still doesn't trust multicoat! He said that CR39 would never be as popular as glass!

Corey.

[Alan W]

Chip
I am not authorized to mention the company name as I am no longer with them with respect to this issue. However, here in Houston, the largest chain back in 1997 -98 had a customer rejection rate of about 6% on poly lenses over 3Diopters minus and slightly higher on plus. That's very small. But, it's enough to make us smarter in advising our patients. Interestingly, the info came from a lifestyle sales study, and the figures showed that over 70% of the rejections were from people who spent a greater amount of time outdoors due to occupation. My statements above to JimG were erred in that the statements came from "truckers" in Houston not in Minneapolis. I note that JimG's company does far less business in the south than in the North (I know those people very well and the company is highly reputable). We come from all over the country on this board and our experiences can and will vary regionally. As I said in the past, I have been in seven major markets and I have learned to be very careful about generalizations supported ostencibly by scientific data. The classic case is in sun glass tints. Regionally, due to weather conditions, Brown is favored over gray and vice versa. People who transfer from market to market don't always change lens colors. But the locals behave by adaptation. I won't get into Darwinian debates, but we should be aware of the diversity of preference and reaction on a regional if not intercontinental basis. Science be damned . . . people rule and the finest of clinicians know it. And, don't think the lens buyers in several of the chains see the buying behaviors statistically vary from market to market. This is NOT an issue of what's good and what's not good. Its an issue of the human equation throughout the optical industry if not other industries in general and its been that way since dirt!
My apologies to JimG. But, when you put wholesalers and clinicians in the same room, you have the potential for dents in at least two of the walls! If the clinicians also have big pretty labs with state of the art machines to grind them, then the scales of experience tend to tip toward the clinician (who can also be a nasty thing like a retailer).

[Jim G]

Geez, I was ready for more fights...come on, I know you're out there!

First, any posting I make here is as an individual and has absolutely no connection to Walman Optical other than I work there and base my experiences on Walman's experiences...and resourses. When someone is discussing a chain, I obviously take it to mean that individuals position, not the chains. Please give me the same consideration.

Alan, I used the caveat about "talking down" not to demean anyone but to try to overcome prejudice by presenting "facts" upon which someone can then make a more informed decision. I acknowledged that upfront knowing that I would affront someone. I am sorry.

Re: fringe colors. Yes, your truckers would see those, particularly in higher powers...BUT, not to any greater extent than with 1.60 or 1.66. And, no, poly is not for everyone. That's why we have professionals like you folks to recommend solutions to your customers. I will stick to my contention tho that poly is today's best value for the average patient.

For PBS. Dents? Huh? Yeah, it will dent if you hit it with a hammer. I used to give some talks on poly. One of my lines was, "Prescribing poly for safety reasons gives us a "good news, bad news" sceanario. It will stop a bullet! But, you'll have to retrieve the lens from the back of the guys head!" In the early days, and still today for many dispensers, poly was only used for kids, safety glasses and those involved in sports. This naturally resulted in higher returns for abuse; that's the only environment they were used! Put 100% of CR-39 into that environment and you'd see the same results. Our experience with 1000's of pairs of poly show a return rate equal to other materials.

You're probably doing this but poly should be edged dry on a diamond wheel using water only on the last revolution. This will minimize any build-up while giving you a good looking edge.

Lastly, high index lenses are wonderful. They just cost more than poly.

Pete. On heat build-up during surfacing. Absolutely correct. I believe we may have pioneered many of the surfacing techniques used today for poly. And, I guaranty you that we have probably broken more poly than any other wholesaler in the country. We actually melted many of the old blanks using the standard plated wheels. We then developed a fly-cutter that worked wonderfully and virtually eliminated the heat. Even sold it for awhile as the "Cool Tool." Using modern lab equipment, heat build-up is really no longer an issue.

Finally, Chip regarding a test of CR-39, glass and poly. Providing the powers were under +/- 4.00D, poly would win hands down. And, that constitutes about 90% of your customers. Consumer test after consumer test shows that light and thin wins every time. Your patients could care less about abbe values.

Thanks, I feel better now.

[This message has been edited by Jim G (edited 04-06-2001).]

[Ryan]

I think you hit the nail on the head. Jim, you mentioned hi index lenses are great, but they are more expensive. I think that is the bottom line, is the cost of the lens. If poly and high index were the same price, I think more people would prefer to use hi index. You mentioned that there is no problems with polycarb until you get to a +/-4, so you are telling me that a person with an RX of
-0.50 -2.50 003
-0.25 -3.00 009
that poly would be the same or better than a 1.56 or 1.60 hi index?

[Jim G]

Ryan. The mid-index lenses have a somewhat higher abbe than poly. Therefore, theoretically slightly less chromatic aberration. However, the difference should be undetectable to a user in that power. The abbe for 1.60 is so close to poly that the optics would be virtually identical.

[Alan W]

Jim G
Thanks for the clarifications. I am an "80% poly" person and believe, as you do, it is the best value for the average rx. As for prejudice . . . I suppose one might say a doctor prescribing Celebrex over Viox is prejudiced, especially if he has had too many patients come back with problems. But, I dare say that prejudice is not professional discretion unless the drug rep is a drop dead knock out! However, in the case of the exceptions to the rule as in the "trucker" situation (and, I might also add from personal observation, some photographers like in video who are RGB sensitive, and some artists) there are those situations when we practitioners will exercise professional discretion. But, again, professional discretion is NOT prejudice. In all other ways, as you described, I am in agreement. And, yes, economics is a factor. I just can't help but believe that in some situations, regardless of the bucks, the coated hi X is a pretty elegant piece of optics over coated poly. Remember now . . I'm an 80% poly person. Let's keep it in context.

[UtahOD]

I for one do a lot of poly and patients love it. Anyone around -2 to -4 or so is great, and a good aspheric does wonders. Hyperopes do very well in it, as well.

The local Hoya rep came around talking about a new material called Trivex. He claimed it was as strong as poly with the optics of better materials.

Here is a link on it:

http://www.visionmonday.com/NewsItem.cfm?AN=5712&Cat=5

[sandeepgoodbole]

Originally posted by lguess
[B: If I would have had glass or even CR39 lenses my injury would have been a lot worse. I'm definitely a poly wearer from here on out. BTW, my wife says my new scars make me very rakish looking, and she'll love me anyhow-
Larry [/B]

I have do have a different prediction.Had it been glass, it would have broken in to pcs.Projectile Splinetrs might have missilled on some other targets of your face. So,likely, you would had a distributed injuries rather than pin point bloody fountain. Had it been Cr, probabaly, it would have protected you well by Jihading itself in two parts and falling apart quietly.

[Jeff Trail]

Oh some fine points made BUT lets look at this a little closer shall we? Their are a number of things that seem to not have been mentioned here.. First, I can tick off a number of opticals that push poly for every RX, and the higher the RX (+/-) the MORE they push it. Next, lets face it not ALL poly is the same and NOT all manufactures process it the same way, I can also tick off a list of companies that make FSV poly's that vary widely in distortion.
I can even see Pete jumping up and down here (Hi Pete:-) BUT Pete has even stated he likes to farm out the uncut poly because of inconsistency during grinding..I as a lab owner have seen a number of problems arise from this as well, of course if you ask the "lab guy" they will say.."oh no problem, whip them out just like CR39 with low breakage".. and as someone in the lab to long I know better. If they are doing it, out of the 40 or so lab owners I know they are in a class of their own if they have a low breakage rate as CR39(that includes those nasty scratches before you get to backside it).
In the perfect world poly being ground would meet the threads expectations, other than the one where the was it impact of unequaled something or another, sorry Jim forgot the exact phrase, but Tri-vex is not mentioned which happened to actually test slightly higher :-) but they didn't even claim that just claimed it as impact resistant.
I always say it's not the base product (other than some types of poly production are differing cold/hot cast, cold cast being far superior) it's what is done to it AFTER the casting that makes the bigger difference.
Same applies to PAL's it's 95% fitting.. I have had opticians tell me all the time that they won't try that PAL because they are junk, but when you get right down to the actual numbers between the very best to the worst there is not really that big of a difference, till you get into front wave technology.. oh their are some but since we like to use "well I" here, I did do a bunch of combinations when converting a lot of my accounts from Varilux Comfort to Natural's where I put both RX's in each material in the exact frames and not one OD or optician I did it for could pick one over the other in difference, trying them on. Other than one is less expensive at the end of the month than the other.
So a sitting poly is nice, but the problem is in producing it..no matter what anyone wants to say poly's are a touchy lens to produce and are VERY heat sensitive in the lab process.. on paper theoretically it may have all the right numbers but in real world production you have a lot of swings in those numbers.
BTW I was kind of insulted as well from the original posting, since I seem to be one of the few lab people on here who seem to dislike poly because of the reasons I have just stated and have done so numerous times. I love the theoretical side as much as the next guy, but I know real life production at times tosses those numbers out the window.
I have done a number of the tri-vexs(mostly Youngers Trilogy version) and wish the price of it was lower because for ease of use and running it beats the pants off of poly production.. if that does come down once the lic. runs out to Younger and Hoya and other companies get to tinker with it than I would love to see it come into the poly cost range and you won't have to just shake your head when you get that order for +8.50 in poly,
OK, you had the gloves off and seem to know more than I about poly so start bashing :-) Nothing I love better than a good debate, just seems I'm always the one who stands out there and takes the beating around here..especially in the "political" ring..:-)

Jeff "let me have it, maybe we can put it on pay per view" Trail

[chip anderson]

If it's so damn good, why can't we get Executive Bifocals and aphakic corrections for the kids that need the protection of poly so bad?

Chip

[Johns]

Everyone that gets glasses from our office signs a form that states they were offered poly lenses (if the rx is available in it) as a legal measure.

We fit 90% poly and have a (big guess here...) 1-1.5% failure rate. It has come a long way in the last 10 years.

No arguement here...

[Dale]

Sorry,

No argument here on poly. lenses. I started fitting them in the late 80's and yes there were problems with them at that time. I also remember the issues with CR39 when they were first introduced. ( Jeez I've been around a long time) But thanks to the many wonderful lab people out there it was soon taken care of.

I have been wearing poly. plz sunglasses for the past 4 years with no problems and I also wear poly., ar coated lenses and still no problem. I have encountered very few people including high minus RX'S that have had an issue with the material. Of course I always pre-adjust all my frames and double check the pd's & oc heights.

I do like poly, but on some patients I do fit Hi- Index. It's all about lifestyle dispensing.

Just my 2 cents.
Dale