In the process of choosing cosmetic contact lenses, it is best to choose cosmetic contact lenses with high oxygen permeability. In the international contact lens industry, the standard for judging whether contact lenses can be worn overnight is that the oxygen permeability of contact lenses must exceed 125, so the oxygen permeability higher than 125 is within a relatively safe range. It is suggested that it is best not to wear cosmetic contact lenses for more than 8 hours regardless of oxygen permeability.
Generally speaking, the thinner the lens, the higher the water content and the higher the oxygen permeability, but this is not absolute, and the oxygen permeability is also closely related to the material of the lens itself. To detect the accurate value of oxygen permeability of contact lenses, it is necessary to go to a professional testing institution to measure the value.
Concrete concept
Corneal energy metabolism must depend on adequate oxygen supply. When the contact lens partially or completely covers the cornea, there are three ways for the cornea to get oxygen: draining tears, infiltrating tears and combining materials. The oxygen permeability of contact lenses depends on two factors, namely the material and thickness of the lenses. The ability of lens to allow oxygen permeation is called the oxygen permeability coefficient of lens, so the oxygen permeability of soft lens is directly proportional to the water content of lens and inversely proportional to the thickness of lens.
The permeability of materials is calibrated by DK value, and the oxygen permeability can fully improve the oxygen supply rate of high-energy glass. For people who wear contact lenses all day, the oxygen permeability of contact lenses needs to be greater than or equal to 35 degrees, which is equivalent to a minimum oxygen permeability of contact lenses. Of course, the higher the oxygen permeability of contact lenses, the better. If the oxygen permeability can reach 125 degrees and reach the standard of continuous wearing for many days, then the eyes will be healthier.