The biggest problem is the size of the frame. Vision 20/20 Protocol Review In order to house two lenses within a single frame, there is a need for the lens to have sufficient vertical distance for the prescription to change. There are ways around this though. Many varifocal prescription glasses require a height of at least 25mm so as to function properly. Now though, you can often buy short corridor varifocal lenses that can be housed in frames less than 25mm high, and often as small as 13mm.
You may also select from a range of lens thicknesses. For stronger prescriptions the lenses in standard varifocal glasses tend to be quite thick which some wearers find unattractive. For infrequent wear, this doesn't particularly matter, but if the glasses are your main pair, you may consider a thinner alternatives. A standard, thinner varifocal lens is the 1.6 option. For ultra-thin, you can choose a 1.67 premium varifocal lens. Lastly, if you want the absolute thinnest lens currently available then you might wish to try the 1.74 grade. As you might expect, the thinner the lens, the more expensive they get, so it's worthwhile giving some thought if you really must get the more expensive lenses.
As with other types of glasses, coatings are available for varifocal lenses such as scratch protection, anti-glare coatings, and sunglasses tinting. As varifocal lenses are usually a factory order, some coatings are not available on all lenses. This may affect your choice as to which lens option to select, depending on your requirements.
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