Contact lens moisture content detailed
The water content of contact lenses is a very important parameter. Today, author is specifically for the water content parameter to answer your questions.
For the definition of water content, I believe we all know more about it - refers to the percentage of water in the total weight of the contact lens after the material is saturated with water absorption. The water content of the traditional annual and half-year dumping is generally 38% and 40%, which belongs to the relatively low water content, while the short-cycle discarding type is generally 50% or more, which belongs to the high water content.
In theory, the higher the water content, the more moist and comfortable the lens will be. But in the actual wearing process, because the lens itself does not produce water, then after the water evaporates, the contact lens will absorb tears to replenish water. Therefore, high water content also means that the evaporation rate is faster, which is more likely to lead to dry eyes, and the water retention of low-water contact lenses is stronger. Therefore, we can not simply understand that high water content contact lenses are better, if easy to dry eyes, you need to choose a lower water content contact lenses.
The relationship between water content and oxygen permeability varies slightly depending on the material. For hydrogel contact lenses, oxygen permeability is basically dependent on water content to achieve, water content and oxygen permeability is proportional to the relationship, and oxygen permeability is greatly limited by the upper limit of water content. However, for silicon hydrogel contact lenses, the delivery of oxygen mainly relies on silicon molecules, and is no longer affected by the decisive water content, so oxygen permeability has been greatly improved.
To achieve the dual requirements of safety and comfort, the water content must be carefully considered, and the appropriate value should be selected according to the tear secretion situation. At the same time, the parameters of contact lenses affect each other, and we can not only focus on water content and ignore other parameters!