If you want your eyeglasses to be lighter in
weight then you should use organic lenses. The organic lenses are
much lighter then the crystals and they also do not break. If you
use to do sports with your eyeglasses then it is neccessary to use
the organic lenses for protection purposes. The same is valid also
The disadvantage of the organic lenses is that
they might need to be replaced more often because they tent to get
scrached more easily than the crystals. That depents of course on
the use that you make of your eyeglasses. There is a special antiscrach
treatment for the organic lenses to avoid the scraches on the lenses'
surface. This treatment helps very much but the inorganic lenses
have still a harder surface than the organic ones.
The refractive index of the organic lenses can reach the 1,7 therefore
they can be as thin as the 1,7 crystals. But the crystals can get
much thinner, because we have inorganic materials with a refractive
index up to 1,9. That means that the organic lenses can't be as
thin as the inorganic ones.
The antireflective coatings can be done also on the organic lenses
in order to be clearer and better looking.