Soft contact lenses are divided into two classes depending on the material from which they are made: hydrogel and silicone hydrogel.
The first soft contact lenses were made from hydrogel, and it continues to be used in their production. This is a polymer whose feature is high moisture content. It is biocompatible, so it does not cause a rejection reaction, it feels very natural, you quickly get used to it.
The oxygen permeability in this material depends on the water content. It absorbs moisture, but does not allow oxygen to pass through, so water performs the function of oxygen saturation. The more water, the more oxygen enters the cornea of the eye. However, moisture should be no more than 80%. If this value is exceeded, then the lenses will not be able to keep their shape and it will be impossible to wear them.
Many consider them more comfortable due to the smoothness of the material and high moisture content. They do not have the feeling of a foreign body and a film on the eyes. The main disadvantage is the low level of oxygen permeability. For this reason, it is not recommended to sleep in them.
There may be different scheduled replacement periods: one-day, two-weeks, < a href="/catalog/ezhemesyachnye-linzy/">monthly, quarterly. They are perfect for daily use, if worn up to 8-12 hours. With longer wearing, there may be a lack of oxygen for the eyes, an increase in the frequency of blinking, irritation and other unpleasant sensations. It is believed that silicone hydrogel lenses, which have a higher gas permeability index, are more suitable for prolonged mode.
It is necessary to have an appointment from a contactologist: it is the doctor who, on the basis of many data, determines the brand, material, generation of contact lenses that are suitable for you personally. In optical shops you can have your vision checked by a professional ophthalmologist and get a prescription.
Knowing the brands that suit you and having a prescription, you can buy lenses in online stores and lens mats.