So I have -4 for both of them, which results in -8 in total (same for left and right eye). At my optician, I have to choose the best package they have to make sure my sunglasses can be as light as possible (30% less thick). Now there is a problem, I wish to have my sunglasses polarised as well but they said it will make the glasses thicker, but I still can make it thinner again by buying an extra package for 45% thinner, so it may be as thin as the original glasses without the polarised option.

I don't know much about how physics behind how the glasses are made. But can someone help me to verify if my optician is being honest or it is just a trick to sell more products?

  • $\begingroup$ For those unfamiliar with the design of lenses to correct for astigmatism, see en.wikipedia.org/wiki/Toric_lens Xitrum's lenses range from -4 to -8 dioptres, i.e., they have a -4 spherical component combined with a -4 cylindrical component. $\endgroup$ – PM 2Ring Mar 26 '19 at 12:45
  • $\begingroup$ As an aside, are you sure that your eyes will be ok with polarized glasses? As my eyes got worse and my astigmatism increased I got to a point (well before your situation) where I could not stand polarized glasses (eyeballs would freak out, bad vision, headaches from just putting on polarized glasses). $\endgroup$ – Jon Custer Mar 26 '19 at 14:38
  • $\begingroup$ @JonCusterThank you for the concern. I will be fine with it :) my old one was a polarized one and i didn't have any problem with it $\endgroup$ – Xitrum Mar 26 '19 at 14:53
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    $\begingroup$ I'm voting to close this question as off-topic because it's about verifying the claims of medical professionals and not physics. $\endgroup$ – Kyle Kanos Mar 26 '19 at 21:59
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    $\begingroup$ If you are concerned about the practices of the optician you have, go get a second opinion from another optician, not random strangers online. $\endgroup$ – Kyle Kanos Mar 26 '19 at 22:00

There is no core physics reason why this should be the case. The polarizing layer is a coating which does not contribute any appreciable thickness or weight to the glasses - and particularly once the glass is in the thickness range that you mention.

At best, it could be conceivable that the thinner lenses are made from a different type of glass which does not work well with the standard coating, and that the coatings that do work with that type of glass are more expensive. But, frankly, that sounds rather unlikely to me. (At best, those inflated prices will be due to economy-of-scale effects more than anything grounded in physics.)

The simple answer, however, is that the pricing on glasses has nothing to do with physics. The opticians market is deeply uncompetitive (see e.g. the references here as a starter) and the pricing is controlled by what the consumer is willing to pay, with only thin links to the price of production. For your situation, I would recommend shopping around on a wide canvas of the outlets in your area and online.

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No. Polarisers are typically a few mm thick. The nanorod package is probably outside of your price range.

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    $\begingroup$ "A few mm thick" for the polarizer filter? Where have you seen such a thing? $\endgroup$ – Emilio Pisanty Mar 26 '19 at 12:09
  • $\begingroup$ so it should be thinner ? $\endgroup$ – Xitrum Mar 26 '19 at 12:12

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