What are soft and hard contact lenses?

Selection method of soft contact lenses Selection of soft lenses: Soft lenses can be divided into traditional types, frequent replacement types and discarded types. As the choice of spherical soft mirror, especially for the first time, it is generally recommended to choose frequent replacement or scrapping type. The center thickness of the lens usually starts from the standard thickness. If the lens has a high degree or is worn for a long time, it can start from the ultra-thin type to increase the oxygen permeability. If the operation ability is poor or low, it is less than 2D. Standard thickness lens or thick lens can be selected, and the water content starts from low water content. Selection of soft lens parameters: the total diameter of the lens is larger than the diameter of the cornea, and the ideal moving range is 0.5 _- 1.0 mm, which is commonly used at present. 14.2。 14.5 mm. The basic curved lens of the lens is worn in the eye, which requires the lens to move with the blinking surface to a certain extent to ensure the exchange of tears under the lens and the discharge of corneal metabolites. In order to obtain ideal mobility, the base arc of the soft mirror should usually be flatter than the reading of the corneal curvature meter. Lens power: It depends on the result of optometry. If the diopter is greater than 4D, the vertex effect of the lens should be considered. You can look up the conversion table and work out the equivalent spherical lens. However, the final power of the lens is determined according to the fitting of the lens and the optometry after evaluation. Rigid contact lenses mainly refer to breathable rigid contact lenses, which are one of the two major types of contact lenses. Hard lenses have their own unique properties in design, manufacture, materials and fitting concept. In clinical application, it is similar to soft lens, such as correcting ametropia, and has irreplaceable application value, such as oxygen permeability of lens material, excellent optical properties, good corneal astigmatism correction, refractive correction of keratoconus and other corneal diseases.