During last 10 years rimless glasses became very popular. But not everybody knows that they have been extremely popular even 100 years ago! Honestly that popularity wasn’t because of fashion. Now we are going to tell you about the history of that kind of glasses. In the beginning of the XX century lenses were made from mineral glass, and had a big weight, and if to multiply the weight of the frame, it wouldn’t be convenient to wear such super-glasses. In addition, frames were so massive and not good-looking, and frequently were not comfortable. With developing of the manufacturing it appeared an opportunity to produce lenses using more light materials, but rimless glasses were still in fashion. Now there are two types of rimless glasses: semi-rimless and rimless. In semi-rimless glasses lenses are fixed by nylon fishing line, screw and other fastening devices. In glasses without ring it’s often used screws that are screwed into the holes on lenses. Good and quality rimless glasses may cost little bit more than glasses with plastic or steel frame. It depends on special manufacturing. The fact of the matter is that for creation the high quality glasses it’s necessary to follow many standard specifications – they must be convenient, light, strong, safe. Not every material will be good for lenses and in rimless glasses the most important parts are exactly the lenses. For example the producers of rimless glasses flatly refuse from mineral glass – it is very brittle and has a big specific weight. But polycarbonate is in high requisition, because it’s very light and strong. Besides, it’s very soft, this makes the processing more easily, and it has a high refractive index and absorbs ultraviolet rays in range of UVA and UVB. Some years ago optician started using synthetic material called Trivex. It’s more light and impact resistant than polycarbonate. But the most popular material for manufacturing of lenses is CR-39. This material is widespread, but it’s not a high quality one. It has some fundamental defects. First is low reflactive index – because of this it’s needed to make lenses more thick, that is the reason for difficulties while manufacturing. Second is while comparing CR-39 with polycarbonate or Trivex, the CR-39 yields to them with impact resistance.