polycarbonate v. high index lens

[nelce]

hey guys, i was just wanting to seek some advice regarding my lens. i recently put in an order at pearlevision to have my glasses & lens made. my prescription is OD -8.75, OS -6.25. i am seeking the thinnest and lightest lens possible, and at pearlevision, they told me their "microthin plus" lens made from premium polycarbonate is their thinnest lens. however, i'm hearing from many sources that the high index lens is even thinner? is this true? when i confronted pearle vision about it, they told me they use "polycarbonate plus" which is thinner than high index, and that high index is only thinner than ORDINARY polycarbonate.

here is pearle vision's website on the microthin plus lens: http://www.pearlevision.com/webapp/w...&storeId=10001

any insight on which is thinner for my prescription? these "microthin plus" lens made from premium polycarbonate or the high index lens. thank you all in advance!

[HarryChiling]

They are refering to aspheric polycarbonate lenses, but you can get high index lenses in a aspheric design as well. The high index in an aspheric design is going to be thinner than a polycarbonate.

[RT]

Harry, you're only half right. If you're comparing an aspheric Poly with a 1.0 mm CT to a higher index (1.60, 1.67) that is only surfaced to a 1.5 mm CT, and the frame isn't huge, the poly will be thinner. Note that in the US, most 1.60 and 1.67 products require either a minimum CT of 1.5 - 1.8 to pass the impact resistance standards, or a "cushion coat" to enhance the impact resistance at lower thicknesses.

It is fairly easy to engineer real world situations where higher index does NOT equal thinner.

[OPTIDONN]

If you took an aspheric poly lens with a 1.00 CT and an aspheric 1.66 to a 1.70 high index with a 1.5 to 1.8 CT I feel pretty confident that the high index lenses will be thinner than the poly.

[OPTIDONN]

Also keep in mind that the higher the index the less curvature is needed. This will result in a thinner profile. Going by CT is not the most accurate way to judge a lenses overall thickness.

[Robert Martellaro]

Due to index of refraction alone, 1.66 is 12% thinner than 1.586 (poly). 1.66/1.67 is available with a 1mm center thickness (finished).

[nelce]

thank you all for your replies :)

so i called up costco..i was thinking about transferring my frames to fit the lenses there...they sell a 1.67 high index lens. will this be a thinner lens for my high prescription compared to this aspheric polycarbonate lens that pearle vision is offering me? i don't really have any information on the CT though...

[Happylady]

thank you all for your replies :)

so i called up costco..i was thinking about transferring my frames to fit the lenses there...they sell a 1.67 high index lens. will this be a thinner lens for my high prescription compared to this aspheric polycarbonate lens that pearle vision is offering me? i don't really have any information on the CT though...

The thinnest lens you can get in the States is a 1.74 high index. Generally speaking the higher the number the thinner the lens. With your prescription the 167 should be fine, though.

[OPTIDONN]

thank you all for your replies :)

so i called up costco..i was thinking about transferring my frames to fit the lenses there...they sell a 1.67 high index lens. will this be a thinner lens for my high prescription compared to this aspheric polycarbonate lens that pearle vision is offering me? i don't really have any information on the CT though...

Keep in mind that the change in thickness MAY not be extreme. Depending in the amount of asphericity etc. etc. that vary from one manufacturer to another it could be as little as .5mm to 1.5mm.

[AWTECH]

Unfortunately the question you are asking can not be properly answered here since there are so many variables.

My company produces lens from 1.67 MR-10 using freeform surfacing technology and are custom made aspheric design rather than a premade aspheric design and the way we process a 1.67 lens will result in a thinner lens than the traditional 1.67 aspheric processing. We place the aspheric design on the back surface and this will result in a thinner individualized. Using traditional methods for making the lens you could get two different thicknesses from two different labs based on each labs production standards.

The type of retail opticals you mention will offer you good basic quality lenses, however for specialized products, few of these type of retailers offer specialized products such as the lenses that my company makes. Different labs have different center thickness minimums.

With your strong prescription you may want to consider a truely custom lens that is individualized. These will cost considerably more than a traditional aspheric design, so it depends on how much you are willing to pay for the thinnest lens possible.

[mirage2k2]

what about optical quality? I made the mistake of going for the thinnest lightest thing that money could buy and ended up with lenses that gave me eyestrain because the vision was not good enough ... the fact that they cost SO MUCH just rubbed salt into the wounds My advice, for what its worth, get the thinnest lense that also provides good optics ... with rx OD -8.75, OS -6.25 I would not touch polycarbonate or 1.74 ... go for a good 1.6 ... Hoya eyas, Sola finalite ... the ones with ABBE above 40.

[OPTIDONN]

Chromatic aberration can be annoying but in general will not riun the optical quality of the lens. I would be more concerned about marginal astigmatism created by a well meaning optician by selecting a base cure thats too flat in order to make the lens thinner. Besides if the eye is well centered and the frame small enough the chromatic aberration will be minimal.

[AWTECH]

Mirage2K2: Unfortunately many people blame Abbe Value for their adaptation problems, when in fact there is no equipment at the optical retail level to prove or disprove this.

For example I would estimate that more than 99% of the Rx jobs filled in both 1.60 and polycarbonate if surfaced in the same manner to the same standards would provide comparable vision. Abbe value is not the problem in over 99% of the cases even though it is pointed to as the problem.

I would be curious to know in your cited example how you concluded your vision problem was related to Abbe Value.

[OPTIDONN]

Mirage2K2: Unfortunately many people blame Abbe Value for their adaptation problems, when in fact there is no equipment at the optical retail level to prove or disprove this.

For example I would estimate that more than 99% of the Rx jobs filled in both 1.60 and polycarbonate if surfaced in the same manner to the same standards would provide comparable vision. Abbe value is not the problem in over 99% of the cases even though it is pointed to as the problem.

I would be curious to know in your cited example how you concluded your vision problem was related to Abbe Value.

You have a good point. Chromatic Aberration is probably one of the better known aberrations by both eye care professional and consumer alike. As a result I think it get blamed for alot of things that are totally unrelated.

[Diane]

MR-10 with index of 1.67 has superior optics, super thin, better tensile strenght, superior solvent resistence, more resistant to temperature extremes....better than poly.

You'll pay more for it than poly, but it is a better product.

Just my 2 cents worth.

Diane

[For-Life]

Here is the thing, what is the rx? What is the PD? What is the frame size? Ect.

Even add to that the centre thickness and such. Are we really helping this consumer thus far? Probably not. Lets get our answers to be answered by the fitters, and maybe give the poster some guidance.

[mirage2k2]

I would be curious to know in your cited example how you concluded your vision problem was related to Abbe Value.

... sorry guys forgot to mention my 5d base out prism ... which does give me considerable trouble with my +6 rx in 1.74 lenses. The sharpness of the vision is definately affected by the amount of prism ... and although my optician has not been able to measure the amount of chromatic aberration, as AWTECH has suggested, they have made several lenses with differing amounts of prism and the ones with lots have poorer vision than the ones with less ... for example, with a 4d left the chromatic aberration (mainly color seperation) is clearly visible when I look straight on ... I dont even have to look off-axis to see it ... thanks to the OC already being displaced by several mm.

In this thread I saw the rx of -8 or so and thought ... off-axis vision ... lots of induced prism + low abbe = lots of chromatic aberration.

[AWTECH]

Mirage 2K2:

You could be seeing different colors as you describe due to hard coating. I assume you have hard coating and anti-reflective treatment. I doubt that the lenses are processed with a hard coating with an index of refraction greater than 1.60 and it may only be 1.50. This hard coating differencial could be why you are seeing different colors in certain viewing angles.

A lower index lens material with matched hard coating may stop the problem. You could find that a hard coating of 1.60 on Poly could eleminate this issue even though you would have an abbe value that is not that high.

Conclusions about abbe value that many people draw is like conclulding that if you drive down the road you are going to die. You can make this conclusion about dying if you use the following premise. When I drive down the road I may cross the center line at the same time a large bus is approching at high speed. Based on these facts you are likely to die driving down the road, however the number of people who cross the center line at the exact time a bus is fast approching is a very small percentage of people driving.

My above example is to point out that there are many factors that can cause one to draw an incorrect conclusion and without the method to test your premise that the abbe vaue of the lens is the problem, there is no basis to conclude that tht problem with your vision is caused by abbe value.

As OptiDonn stated:

Chromatic Aberration is probably one of the better known aberrations by both eye care professionals and consumers alike. As a result I think it gets blamed for alot of things that are totally unrelated.

The original question of this thread? The tinnest lens possible is going to cost considerablly more than the lens that was recommended. Thsi recommendation could have been made due to the patient statements during the fitting that he wanted a total cost within a certain range. Let a competent eyecare professional guide you with your total selection and do not think that you can become an expert by seaching the internet and asking a question and getting a total answer on line. Without seeing the patient and the total sum of the information at the same time a proper recommendation can not be made. The answer to your question is quite different if cost is not object, vs. you have a specific budget range.

[OPTIDONN]

MR-10 with index of 1.67 has superior optics, super thin, better tensile strenght, superior solvent resistence, more resistant to temperature extremes....better than poly.

You'll pay more for it than poly, but it is a better product.

Just my 2 cents worth.

Diane

Superior optics? OK I use this phrase all the time with out thinking about it. Aside from abbe how would these other materials have better optics? And how much does abbe affect the optical performance of the lens? Design and physical properties may be better but these are seperate from the optical properties. I think I should stop using that phrase and come up with something else.

[OPTIDONN]

... sorry guys forgot to mention my 5d base out prism ... which does give me considerable trouble with my +6 rx in 1.74 lenses. The sharpness of the vision is definately affected by the amount of prism ... and although my optician has not been able to measure the amount of chromatic aberration, as AWTECH has suggested, they have made several lenses with differing amounts of prism and the ones with lots have poorer vision than the ones with less ... for example, with a 4d left the chromatic aberration (mainly color seperation) is clearly visible when I look straight on ... I dont even have to look off-axis to see it ... thanks to the OC already being displaced by several mm.

In this thread I saw the rx of -8 or so and thought ... off-axis vision ... lots of induced prism + low abbe = lots of chromatic aberration.

OK 5 diopters base out with a +6.00 rx that can make you crazy! My rx is around a -4.00. When I worked at Lenscrafters I had a pair of safety glasses made in poly. I chose an aviator shape, don't asky why!. The excessive thisckness created significant chromatic aberration. It really did not affect the optics of the lens but I found it very, very distracting.

[nelce]

hey guys. i just got my glasses from pearle vision, and on the receipt mentioning what was done to the lens, there's a number under the "cylindrical" and "axis"? I thought these values were astigmatism, which I don't have...could these values mean anything else?

[OPTIDONN]

hey guys. i just got my glasses from pearle vision, and on the receipt mentioning what was done to the lens, there's a number under the "cylindrical" and "axis"? I thought these values were astigmatism, which I don't have...could these values mean anything else?

Nope! they are for astigmatism.

[nelce]

thanks for your reply. damn it, pearle vision just keeps screwing up. and i wore those glasses for an hour or so...feeling weird....i hope they didn't make my vision worse :(

[loncoa]

It's the optometrist who would have prescribed the cylinder in your prescription. I expect that you DO have astigmatism, but if you doubt it, or if you wear the glasses for a week straight and they don't start to feel fine, you need to contact the optometrist.

[nelce]

It's the optometrist who would have prescribed the cylinder in your prescription. I expect that you DO have astigmatism, but if you doubt it, or if you wear the glasses for a week straight and they don't start to feel fine, you need to contact the optometrist.

um. actually i don't. and my prescription ALSO says that i don't. pearle vision is the one who ADDED the prescription for astigmatism in my lens.