Before the invention of glasses, people's lifestyles and professions were constrained by their visual abilities. With the invention of printing and the increase in reading time, the demand for eyeglasses online for cheap good vision has become even stronger.

The continuous improvement of consumer demand has promoted the development of lens technology. Why lens? Because the earliest lenses were flat-convex lenses with a bean-like appearance, the English name for lenses is the lens.

Nowadays, there are eyeglasses online cheap lenses made of different materials with different refractive indices to meet the needs of different groups of people. For example, PC lenses, high refractive index resin lenses, dyed lenses, etc.

The chemical composition of naturally transparent quartz crystals is mainly silicon dioxide, with a refractive index and density slightly higher than optical glass. Due to poor optical performance and other disadvantages, they are replaced by glass and resin lenses.

The advantages of natural crystal lenses are high hardness, high-temperature resistance, friction resistance, low coefficient of thermal expansion, and moisture resistance. With the development of the glass industry, glass has gradually replaced natural crystals and become a material for making eyeglasses.

The eyeglasses online cheap materials are divided into ordinary glass and optical glass. The optical glass used for making eyeglasses is divided into low-refractive index glass and high-refractive index glass. Nowadays, we commonly use high-refractive index glass, which is replaced by low-refractive index glass resin lenses.

Because glass lenses are relatively heavy, prone to breakage, and have poor impact resistance. Glass lenses can add different elements to increase their refractive index.

Because glass lenses have a higher refractive index and thinner edges after grinding, people with higher heights can choose glass lenses. This way, the assembled lenses are more beautiful, but it is important to pay attention to the safety of wearing and using them to prevent lens damage.