The modern world is very fast and dynamic. Consumer requirements rise to every commodity part of their everyday life - food, clothing, cosmetics, and medical devices. Eye care and eye health are also part of them. Companies producing contact lenses work daily to improve the safety and comfort of wearing, as well as on the technical characteristics of the material (type of material, wear time, module, Dk / t etc.). Silicon hydrogel contact lenses (SiHy) were introduced almost two decades ago. At that time it was estimated that there are about 70 million contact lenses all over the world. Since then, their number has doubled and a significant majority now have silicone-hydrogel contact lenses, resulting in a steady and noticeable reduction in the number of regular hydrogel lenses. When the first one-day silicon-hydrogel contact lenses were introduced in 2008, they were announced as breakthroughs in technology. When they were introduced to the market, they were presented in spherical, toric and multifocal designs, which led to a significant increase in the use / prescription of silicon-hydrogel daily disposable contact lenses. A survey conducted in 2014 by the International Consortium illustrates this point. Although, according to this study, the use of SiHy contact lenses varies widely across the world. In the United States, Canada, Australia and the United Kingdom, four to six times more patients were fitted with silicone-hydrogel CLs compared to hydrogels in 2014 and in each country, daily disposable SiHy contact lenses were prescribed with a larger frequency compared to daily disposable hydrogel lenses. It is important to make a good fit to ensure and increase the comfort of wearing contact lenses. In addition to some of the standard fitting techniques such as: keratometry and choice of base curve of the lens; size and eccentricity; an assessment of the mobility of a lens placed in the eye - look positions, mobility, push up test, can be added and the wetting of the contact lens. Even in perfect fit, if the lens does not interact well with the tear film, it would lead to complaints and discomfort in the patient. The degree of wetting is determined by the balance between adhesive and cohesive forces acting on the surface of the lens. CLs, which can support full wetting, allow a tight coating of the tear film, a smooth recovery of the tear layer after eyelid opening and good visual acuity. The interaction between CL, eye surface and tear film is vital to their successful fit. It has long been known that both the organic and inorganic components of the tear film and anterior surface of the eye can deposit deposits on the contact lenses. There are various non-invasive methods for assessing the tear film and, above all, the lipid layer. Some of these are Non invasive breakup time (NIBUT) and specular biomicroscopy. In the present work we will look at daily disposable silicone-hydrogel contact lenses that have been tested in vivo for good wetting, stability and good regeneration of the tear film.
Contact Lens Materials: A Materials Science Perspective