How big does a lens need to be for progressive glasses?

[San Perlita]

How big does a lens need to be for progressive glasses?

[San Pierre]

Progressive glasses,also called no-line bifocal glasses, help glasses wearers to see things clearly in different viewing distance.The proper height of this kind of lens must be a minimum of 30mm from the top edge of the lense to the bottom.

[San Quentin]

Progressive glasses allow people see clearly from far to near. So a lens of progressive glasses is usually bigger than a regualr one. The common height of progressive glasses lens must be at least 28mm. However, the height varies depending on the type and brand of the progressive glasses.