Physical properties of glasses
Transparency refers to the clarity of a substance. It is a comprehensive manifestation of material chemistry, purity, hydration and other factors. Usually, light of a specific wavelength is used to express the transparency of a substance by the percentage of the transmittance of a substance sample.
The hardness of the material is an important quality indicator, which reflects the manufacturing of the lens and the durability of the lens. The property of hardness is more closely related to hard lenses than soft lenses. Toughness reflects the degree of flexibility of the material. Lenses made of materials with good flexibility feel good at the initial wearing stage, but cannot correct corneal astigmatism, because it is easy to close to the cornea and fit the shape of the cornea.
Tensile strength indicates the maximum tensile force that a material can withstand before it breaks in a stretched state. High tensile strength → good durability.
The modulus of elasticity indicates the ability of a material to maintain its shape when subjected to pressure. Materials with low modulus of elasticity → low resistance to pressure. Materials with high elastic modulus → better resistance to pressure in order to maintain the shape and provide better vision.