Synonyms in a broader sense
Adhesive lenses, adhesive shells, adhesive lenses, glasses engl. : contact lenses
Soft contact lenses
The soft contact lenses are made of flexible materials and lie directly on the cornea of the eye. Their diameter is slightly larger than that of the cornea, so they cannot slip or fall out. There are many different materials from which soft contact lenses are produced, they differ mainly in oxygen permeability, flexibility and handling and water content.
Soft contact lenses are available as daily lenses, monthly lenses and annual lenses. Generally speaking, the longer the lenses are worn, the higher the quality of the lenses. However, most daily lenses are much thinner than, for example, monthly disposable lenses, as they do not have to be as durable and flexible, which often means that they are better tolerated.
Soft contact lenses are often made from so-called hydrogels. The thinner and more hydrous these contact lenses are, the more permeable they are to oxygen. However, since very thin hydrogel lenses with a high water content are not dimensionally stable and are very sensitive, there are limits to the thickness of the contact lenses.
With many soft contact lenses, a high water content also means that water evaporates more easily. The consequence is that the tear fluid is absorbed by the contact lens, resulting in dry eyes. Hydrogel lenses made of Hioxifilcon and G72HW absorb relatively little water and are therefore also suitable for dry eyes. Soft contact lenses made of Lidofilcon absorb relatively little water and are therefore not suitable for dry eyes.
Silicone hydrogel lenses
These special soft contact lenses have a core of silicone and a coating of hydrogel. The silicone core makes them particularly permeable to oxygen, but they are also less flexible and many wearers find them more uncomfortable than pure hydrogel lenses. All soft contact lenses available on the market so far, which can also be worn at night, are made of this material.
The dimensionally stable contact lenses are made of harder plastics and are not flexible in their shape, so they have to be perfectly fitted to be tolerated and not to harm the eye. The diameter of dimensionally stable contact lenses is smaller than the diameter of the cornea, the lens also rests on a tear film and not directly on the cornea. This makes them ideal for slight irregularities of the corneal surface on the one hand, but on the other hand they do not adhere as well as soft contact lenses and can fall out of the eye in case of fast movements or strong wind.
For people who move a lot and do sports, soft contact lenses are therefore more suitable. Because dimensionally stable contact lenses do not seal the cornea and the tear fluid can therefore supply the cornea well with oxygen and nutrients, they are significantly less risky than soft contact lenses. Dimensionally stable contact lenses usually last for several years and are therefore significantly more expensive than soft contact lenses and therefore only suitable for people with stable vision.
