HI all
i denmark where i am from almost no optometrist use polycarbonat, but as i understand it, you guys from the states use it all the time.
what are the reasons that you use it, and how does the AR stick on polycarbonat lenses.
best regards
Peter
HI all
i denmark where i am from almost no optometrist use polycarbonat, but as i understand it, you guys from the states use it all the time.
what are the reasons that you use it, and how does the AR stick on polycarbonat lenses.
best regards
Peter
We don't use MR-6 in the U.S. it's MR-8 for us.
The A.R. on poly is as good as any other material.
Most use it because of the 1.59 index, specific gravity, safety and price.
No other material has all the attributes, most other only have 2.
I don't like working with it because of optics and drill and grooving cracks, sometimes poor SRC depending on the manufacturer.
but you don't used them for 3 pieces right ?
best regards
Peter
We do in the U.S. I dont personally because they tend to form stress cracks along the drill holes which never happens with Trivex, MR-8 or MR-10.
oki great, any idea to why we don't use it in EU, it seam strange to me if its all better.
best regards
Peter Skjold
It's not all good, since poly has an abbe value of 30, which is the worst of any commonly dispensed material. A 1.60 is a good alternative, since most modern versions (MR-6, MR-20) have abbe value of 41 or 42. If a safety lens is truly needed, then Trivex (abbe value about 43) is available.Originally Posted by Mr.Powers
The main reasons why it used so much in the USA are:
- It is pushed heavily by Essilor
- It is pushed heavily by LensCrafters
- The USA is a highly litigious society which allows patients to very easily sue companies, Dr's, opticians, etc when a safety lens (such as polycarbonate) is not dispensed and something happens (car accident, sports injury) that causes eyewear to injure the eye. There are no financial limits to liability or malpractice law suits in the USA (as there are in most countries) and the average medical doctor pays over $100,000 USD in malpractice insurance per year. I don't know how much the average USA optometrist pays in malpractice insurance (I am sure much less), but that is because they regularly recommend polycarbonate to avoid the possibility of such lawsuits. In almost all such lawsuits, the plaintiff lawyers are paid based on a contingency fee, whereby the patient would not pay any legal fees to their lawyer if they do not win the lawsuit, and the lawyer gets about 30% of the settlement if they win. With a glut of lawyers in the USA, many have nothing to do but file such lawsuits against medical providers and companies in the USA.
drill and grooving cracks on Polycarbonate lenses are non existent anymore .........
The drill and grooving cracks on Polycarbonate lenses are non existent anymore for the last 5 years, if you use a drop of "DRILLSEAL" in every hole after drilling, or wipe it on the groove.
See at: http://optochemicals.com/products/info_drillseal.htm
and how does the AR stick on polycarbonat lenses. .................................
The AR sticks well, but there is a big difference as the polycarbonate lens will get totally damaged by AR strippers, the surface will get milky white. No problem with CR39 that way.
yes the law system i hear that before strange thing i USA that the rules are so, based on that no person have to take responsebelity of there own action.
our legal system is based on "Bonus pater" that means the god family father, and by that they mean, what a normal human should know.
coffee is hot, you don't but an animal in a oven etc.
but thanks for the insight , don't really kow how big different abbe value 30 and 41 are i can't se the difference .
best regards
Peter
It depends on the patient Rx. Most with a lower power Rx don't notice differences in abbe value. Abbe value differences are more noticeable in higher power lenses, and in aspherical designs.
I often wonder how often lawsuits are brought on by not using polycarbonate or "safety" lenses. My guess is that the number of lawsuits is extremely small or all but non existent.
I think that is true mainly because most optical professionals are diligent about "duty to warn" when it comes to safety glasses. In the case of many optical shops, they don't have to warn because they pretty much dispense polycarb all the time, unless someone needs a really high index lens.
On the other end, I doubt that there are many incidents where a lens actually gets broken (unless you happen to be Moe Green), so there are not many actual cases where a lawsuit could even happen. But the "duty to warn," or general sales policies of some opticals, are very deeply ingrained in the US industry. Look how long it took for Trivex to be allowed as a substitute for polycarb in cases where a safety lens is needed, and in many situations Trivex is still not even accepted when mandated by government or company policy for certain types of jobs or activities.
Neither can most people (perhaps some extreme rx's). Eyecare professionals here in the States often use this as a reason to not dispense it, when in actuality it is because of reason #2 from m0002a's post above; differentiation from the mass retailers.
dont poly get yellow by time ?
I would disagree with that on two grounds:
- It is not just "extreme" Rx's, but any moderately strong Rx could see the difference with proper A/B testing.
- I think independent opticals don't dispense polycarb every time because customers often want a higher index lens (usually 1.67), and also because of the abbe value. Even opticals like Walmart and Costco dispense mainly 1.67 on high-end lenses.
We almost never make 1.67 a lot more problem whit ARīs and they AR not not that more slim to be honest. i guess 10% are 1.67 the rest is 50/50 on 1.5 and 1.6
Ever since the newer 1.60 monomer with abbe value of 41/42 became available, I think it is the most underrated lens material in the industry.
1.6 monomer never heard of it how offers that ?
1.6 was originally MR-6 with abbe value of 36, but newer versions have been released with abbe value of 41 (MR-8) and 42 (MR-20).
yes that all we use in europ just dint new the name monomer. no reopen shop use polycarbonate, and thats what i am trying to find out why ?
Probably because they are smarter than US opticians, and always use Trivex when a safety lens is required.
but trivet is not as light at poly is it ?
Trivex is slightly lighter in weight in the low powers (Trivex's lower specific gravity trumps Poly's higher refractive index), about the same in the medium powers (it's a wash), and slightly heavier in the high powers (Poly's higher refractive index trumps Trivex's lower specific gravity).
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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