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    Specsavers offer these different options to make your glasses lenses thinner and essentially lighter. I want to know what high index equivalent each option is? High index 1.6-1.9. Which is equvalent to 1.74? Etc.

    I understanf my post is a little confusing. Does anyone know a page that goes in detail on each option? Thank you.

    The free thin and light is either 1.56 or 1.59 (Polycarbonate) or 1.61. (I think it is 1.61, they do mention the up to 40% thinner thing, but it could be just due to aspheric design of 1.56 lenses in + prescriptions.
    1.67 is even lighter, but with prescription under -4 or +3 it would not be noticeable at all.
    1.8 and 1.9 are Mineral lenses and are made for very high prescription for esthetical reasons only, they are heavier than 1.74.

    The lenses thickness goes from 1.499 (standard lenses) which are the thickest to 1.9 Mineral lenses which are the thinnest. Usually the higher the index is the thinner the lens is. However, there are a few exceptions with certain materials and designs, but basically this is how it works.

    Ask them at the store if it is 1.61 or 1.56 lenses, if your prescription is lower than -4 or +3 it will make no difference with a higher prescription lens so go for the free lenses offer.

    I am an optometrist.
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