The lenses are made in a specialised laboratory according to the data transmitted by the optician. They are customized to fit the necessary correction, with the selected material and treatments (anti-reflective and scratch-resistant coatings), the size of the frame and the visual behaviour of the wearer. The lenses are then sent to the optician who fits them into the selected frame.
There are two categories of lenses, depending on the material :
Mineral lenses : made of glass, they are produced from silica glass (extracted from sand) mixed with different elements melted at high temperature.
- : scratch-resistant
- : heavy and fragile
They are not advisable for children and are used by adults less and less.
Organic lenses : half-synthetic, they are made from solidified resin.
- : light and impact-resistant
- : more sensitive to scratches
They can be used with all sorts of frames. Those in polycarbonate are particularly advised for children and sportsmen, because they are both extremely strong and light. They need a special coating in order to be resistant.
Whatever materials they are made of, the lenses are adapted to perfectly correct all eyesight disorders.
In the case of short-sightedness or long-sightedness combined or not with astigmatism, the lenses are called single-vision. They are "simple" lenses that have the same optical focal point over the entire area of the lens.
When you become presbyopic – around the age of 45 – you can wear bifocal or trifocal lenses such as progressive lenses, ensuring ultimate long-sight or short-sight vision.