[QUOTE=Barry Santini;557782]I agree poly has improved over the decades.
But CR39 has not. In fact, its quality has decreased to the point that I will not use it unless I absolutely have to.
Barry...….curious as to what your normal go to material is?
Regards,
Golfnorth
I stock:
Essilor AR poly (EAAR)
Essilor poly (EAA)
Hoya Phoenix EX3 (trivex)
Zeiss Duravision Blu Protect (Poly version)
I order surfaced:
Poly
Trivex
1.60
CR39
1.67
1.74
In that order.
B
The majority of what you state I agree with. I don't think anyone was calling the 1.67 a miracle material and while it may not be much better in terms of it's ABBE value, I have never gotten complaints against 1.67 with regards to visual issues like I've received with Polycarbonate. While CR-39 and Polycarbonate may be the most cost effective solution for a patient, that does not make it the right solution for every customer especially when getting into higher prescriptions. Cost does not enter my mind when helping a customer pick out frames or their lenses unless they make it known that cost is an issue.
Thank you.
Too many “opticians” only see higher indices and expect them to be better, with zero to little knowledge of the actual properties of the material.
High index means I can sell a bigger frame. No. I see this everyday.
Understanding the pros and cons of every material, every frame/lens combo is all I’m asking.
I bend light. That is what I do.
> But, if you want your clientele to become frustrated when their lenses chip and crack, please use poly. They will then become your former clientele.
Classic mistake of associating a product with the business/service. If you sold the glasses and they chipped and the customer is blaming you or your business enough to not come back, you deserve to be out of business. It means you are providing no value customers. All the value is PERCEIVED to be in the product. If the product is bad, you are bad.
IMHO That's a horrible way to run a retail establishment.
Sounds like something someone who has never worked in retail would say. The vast majority of the general public doesn't care about the why, the how, or your "added value". Cost, product, convince, all rank higher to most people in a retail setting. This is coming from someone who owns a very small relationship, type of business. I imagine in a high volume retail setting it is even more skewed.
Further, as an optician or a as customer, I would 100% blame the optician for chipped lenses if they used a material they knew could chip or crack in my glasses when there were better options for the application available. I don't care how good my optician is as replacing chipped lenses. I do care that the optician is smart enough to make glasses with lenses that won't chip the first time.
Let's say you got new tires on your car. You get a flat 2 weeks later and the store replaces it at no charge. Great. 3 weeks later you get a flat on another tire. You go in understandably upset. You speak with the manger who informs you that they are sorry about these tires not working out for you, but they can be predisposed to blowing out on your type of vehicle. Then asks if you would like to get the type of tires that won't blowout on your type of vehicle. You would be ok with this? Are you joking? I would be justifiably irate.
I worked 3 years in retail. Made many mistakes like these. I still do. I know exactly how hard this is. Not everyone can do. Very, very few can do it, effectively, all the time.
Cost, product and convenience are all added values. And they are YOURS, not your product's. Pay attention to what you are saying. Added value is what they care the most. If not, you already lost. They will just buy online. They are talking to you because they think there is a chance YOU (not your products) might add value. They just need to confirm it. You can break their expectations by passing the value over to the product and suffer the consequences of that, or confirm by getting it to yourself. It's all a slight tweak on your language and how do you present yourself.
Last edited by vfpamp; 02-19-2020 at 02:32 PM.
Amen to that !
Seems we all have our go-to's and our biases, eh? Here is a chart that I have been working on for my work group so that they can try to avoid biases, personal or professional.
Yes, its true that there are some that are sensitive to CA. Most are not. It is not always the material. It could be a combination of material, base curve, fit and/or physiology. It could be surface aberrations or warpage. Not just one or the other.
Last edited by lensmanmd; 02-20-2020 at 11:31 AM. Reason: PNG did not populate
I bend light. That is what I do.
Biases are reinforced by the small set of suppliers opticians and labs tend to work with in a recurring basis.
I like the simplicity of the table, but I am not sure how effective it is given the high variability of specs within multiple products of the same supplier.
For instance, when phones are manufactured, each of them go through a sequence of tests to validate their assembly. But failing one of these tests doesn't mean that the phone is not working as designed. For instance, a few tests will indicate memory longevity. Phones that are A quality, have results that inform the memory will last at least 3 years. B, C, and D qualities will last less. One worse than the other. When you buy a phone at a promotion or a discounted price from the main manufacturer, you are getting the C and D phones. They are exactly the same brand and model, they will work as good a the A one, but will present issues sooner than the As and Bs.
Obviously, no one tells the consumers which quality they are getting and most people don't even know there is an internal ranking system for phones. And virtually every electronic component.
The same thing happens with lenses and frames. With in the same type, within the same supplier and the same product line, you can buy A quality or D quality. If you cry for discounts, they will give you the D (pun intended). And those variances are big enough to change the table you have. Maybe the lenses will chip sooner. Maybe the abbe values are not as good due to an extended dying process. Maybe mold was getting old and slightly warped.
And that's yet another reason why opticians diverge so much in their statements here.
This practice is so interesting that some companies only buy Cs and Ds and fix them individually to resell as A-like or B-like.
Last edited by vfpamp; 02-20-2020 at 12:22 PM.
The reality is simply this: The VAST majority of patients can't tell ANY difference WHATSOEVER between the optics of poly or Trivex, or even CR-39, when even remotely competently fit in appropriate prescription ranges. It's that simple. And the amount of CA induced in each material is not mathematically or optically significant to rise to a level that approaches human perception. The math doesn't lie.
If you prefer Trivex for other reasons, and you're able to stay in business with the margins it provides you - great! You get a gold star. If someone else can do exactly what you're doing in the patient's eyes with poly, or CR, or 1.56, or the lid from a take-out food container - great! They're every bit as competent to the patient at the end of the dispense. The tired old Coke vs Pepsi, Ford vs Chevy, America vs anyone else tropes are beyond tired. Let's bury the endless misinformation in the past, where it belongs.
I look at it this way:
1. Poly for everyone because of it's good features. Groovy, thinner, lighter, impacty, UV. A great base lens.
2. High index for those who are bad. (That's really a small number.) 1.67 is not the pick, here, but it's super available so we go with it. The optics are no better or worse than poly.
3. Low index for those who are optical snobs. (That's really a small number.) Trivex is here with CR39.
Remember, all the bad stuff about poly is power dependent. If you use poly right, the disadvantages disappear.
And don't forget, 1.5 CT poly with a FFSV is pretty dang cool.
While I agree with you, and not only with patients, sometimes I can't tell the difference between them myself, I also understand that people will not see the difference *until the appropriate environment highlights their difference*. Chromatic aberration only truly matters in broadband high contrast situations. Until the patient sees, and gets used to the benefits on a good lens and then goes back to a poorer one, he will not know the difference. But once he goes up, he will not like going back. And sometimes it takes weeks for them to notice that they went backwards in quality. By that time, most opticians already computed that patient as one of the "happy ones".
Again, the scenario is impossible, with properly fit lenses. If you're fitting high Rxs in poly, then sure, you get everything you deserve when the patient's wrath comes down. But the reality is EVERY single lens material - including our old beloved glass - exhibits CA. If a pt is *that* picky, a discussion of CLs is in order. But to continue to beat the dead horse, as far as CA is concerned, when properly fit, in a reasonable SRx range, the amount of CA a given eye will experience in poly is literally below human perception. It's in the math. It's easy to show.
Stronger hyperopic presbyopes are very sensitive and aware of the effects of low abbé.
B
Sphere's +3.00 and up = stronger hyperope Barry?
IF Abbe alone were the end all - be all of lens design, every patient would still be wearing glass. Which of course, STILL exhibits CA as well. Just to a slightly lesser degree. Poly is no miracle lens, but as a material, it is unquestionably viable for a VAST number of prescription lenses. But feel free to continue pushing Trivex as the only other option if it makes you feel better at the end of the day. Peace!
Maybe due in part to magnification that decreases the apparent field of vision, forcing the eyes to rotate further to see objects away from the primary gaze, compared to emmetropes and myopes.
I switched many folks from CR39 to Poly when 28's, Execs, and 7x28's were introduced in the early 80's. The results were mixed, with more than a few non-adapts. One case in particular that I'll never forget was a +3ish 7x28 wearer who rejected poly due to blurred text when reading. When I measured the add power the mires were very blurry, but became clearer as I moved the target towards the OC. I had no clue, except to switch back to CR39. That single case drove me to research aberration in lens systems, realizing that many of these lens material failures were due to chromatic aberration, sometimes aggravated by oblique astigmatism.
Twenty years later I advanced to a +1.75 add after spending some time as an emerging presbyope, and acquired my 1st pair of computer eyeglasses. Being a -4.00 myope, I ordered -3.00 SV. I had been using Spectralite (Sola/Abbe 47 density 1.21 grams/cm3) at the time, but the lab said they had Poly with a good AR in stock, to save a few bucks and time I took the Poly. They worked fine, except that I noticed slightly blurred text at the edge of the screen. The base curve relationship was proper, I attributed the blur to CA. Although not good enough for a radiologist, I could grin and bear it. That was the last Poly lens I wore.
So yes, about three diopters of focal power or prismatic power (assuming all the other parameters are optimal), the latter also affecting the vision in the primary gaze, where it's generally accepted that the average threshold value of Lateral or Trans Chromatic Aberration is .1∆. Use the formula TCA=P/A where P is the prismatic effect at the oblique visual point on the lens, and A is the Abbe value of the material used. Use Prentice's rule to determine the value for prism.
Best regards,
Robert Martellaro
Last edited by Robert Martellaro; 02-24-2020 at 07:02 PM.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
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