Types of Contact Lenses

There are different classifications of contact lenses: the material of which they are made, the frequency change (the period after which the lenses are replaced by new ones), mode of wearing (daily, flexible, prolonged, continuous), design (spherical, toric, multifocal), the degree of transparency (transparent, colored, fine). In general, contact lenses are divided into two groups: soft and hard contact lenses. Soft contact lenses are worn about 90% of users of contact lenses in the world. Soft contact lenses are in turn subdivided into 2 classes: hydro gel lenses and silicone hydro gel lenses. Soft contact lenses are often used as daily lenses.

Hard contact lenses are used primarily for vision correction in complicated cases (for example, at high degrees of astigmatism in keratoconus) and in orthokeratology. Rigid lenses allow increasing the visual acuity due to the fact that they retain their shape. Such lenses are rarely used as daily. Such lenses are made of polymers that provide a high degree of transmission of oxygen to the cornea of the eye, so they are called rigid gas permeable contact lenses.

Discount colored contact lenses are used for a radical change in color of the iris, tint, respectively, to enhance or change color. Color and tint contact lenses come in both diopters for vision correction and eye color changes simultaneously, and zero for those who want to achieve only a cosmetic effect. Colored lenses do not affect the color perception of surrounding objects, as in the center is transparent.

There are several methods of manufacturing contact lenses: a centrifugal molding, turning, casting, as well as methods that combine these techniques. Turning it dry polymerized billet is processed on a lathe. With the help of computer programs it is to control receiving lens of complex geometry with two or more number of radii of curvature. After turning the lens polished, hydrated (water saturated) to pass the required parameters and chemical cleaning. Daily lenses are made this way.

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