What is the oxygen transmission coefficient of the contact lens?
When buying contact lenses, there is one parameter that is always mentioned, and that is the oxygen transmission coefficient. Today, author will give you a detailed introduction of what the oxygen transmission coefficient of contact lenses is, and what it will be affected by the factors.
The oxygen transmission coefficient of contact lenses, written DK, represents the ability of oxygen through the lens. Where D is the diffusion coefficient, K is the dissolution coefficient, and the oxygen transmission coefficient is the product of the two. When wearing contact lenses, the oxygen in the atmosphere must first be dissolved in the material to reach the cornea, and then transmitted through the lens. Water molecules and silicon molecules are important "assistants" to help transport oxygen. There is also a parameter, DK / L, which is closely related to the oxygen transmission coefficient, which represents the conductivity of oxygen, where L is the thickness of the contact lens.
The oxygen transmission coefficient is affected by the lens material, thickness, water content and other factors. We often say that silicon hydrogel is an upgraded version of hydrogel material, because the oxygen permeability of silicon hydrogel is several times higher than that of hydrogel. In terms of current materials, contact lenses made from silicon hydrogel have the best oxygen permeability. In addition, when the thickness of the lens increases, oxygen is not easy to pass through, the oxygen conductivity of the lens will be relatively reduced, and when the water content of the lens increases, the oxygen transmission coefficient of the contact lens will increase.
For contact lenses, the oxygen transmission coefficient is a standard to evaluate the quality of contact lenses. The higher the oxygen transmittance, the better the contact lens. At the same time, the level of oxygen permeability will also affect the wearing comfort and safety. Because corneal hypoxia can induce various eye diseases, contact lenses with high oxygen permeability are significant for eye protection. However, we should also pay attention to that, no matter how high the oxygen permeability, contact lenses can not be worn all night!