(1) high light transmission rate of up to 92% light transmission, if the lens coated with one or more layers of magnesium fluoride antireflection films, lens transmittance was 99.2%.
(2) to avoid the UV absorption of UV damage to the eye.
(3) chemical stability in acid, alkali and other corrosive chemicals.
(4) accurate refractive index of 1.523 refractive index constant, constant and accurate, processed and accurate refraction.
Characterized by light optical resin, hardness close to the glass, a refractive index of 1.490. The new high refractive index refractive index of heat hardening resin 1.600, coated with ultra-dura mater and no reflection multilayer film, enhanced abrasion resistance, light transmission rate of up to 98%, and can block UV rays. By the optical resin polished glasses, eye damage easily broken, safety and it is now widely used. Crystal hard wear-resistant material with good insulation, but the UV absorption properties of optical glass than the poor light transmission rate difference, not the ideal material for making optical films, more than eye-candy of high quality goods.
Glasses must be accurate processing of brightness level, made of mirror grinding line with prescription, refractive error is not more than 0.04D-0.09D of the State Ministry of Light Industry of the ministerial standard. Two lens optical center of the pupil distance and the two should also line spacing.
We daily see and wear are mounted on bridge of the nose or ear clip glasses, very convenient. Still others, a greater degree of myopia eyes, other eye a small degree; or one eye to do the cataract surgery, other eye normal. As the two anisometropia too, seeing what a great, seeing what the other is too small, the visual center of them together can not, therefore, can not wear regular glasses. In recent years, there is a wear glasses but can not see, commonly known as contact lenses. It is worn directly on the surface layer of the cornea of the tear lens, cornea and lens in the tear exists between the composition of a liquid mirror. This from the lens, liquid lens, cornea and other refractive eye constitute a new refraction system. In medicine is called contact lens.
Contact lens material according to different lenses, contact lens can be divided into hard and soft contact lens. Hard contact lens by using methyl methacrylate-based glass is made of hard, not easily deformed. Applicable to the correction of high astigmatism and keratoconus. The disadvantage is that ventilation is poor, can not penetrate oxygen, carbon dioxide, water and metabolic substances, wear them uncomfortable. Soft contact lenses are hydroxyethyl methacrylate acid or silicone rubber material, soft, good air permeability, and can absorb water, wear soft and comfortable to use to rule
Corneal treatment, but it is easy to change the shape does not apply to astigmatism.
By way of a wear extended wear and daily wear of the points. Wearing contact lenses overnight, more than two consecutive days for the extended wear, including wearing a type weeks, months or even avoid wearing off type type. Extended wear lenses worn continuously for several days before cleaning to remove one, tear protein and other substances deposited on the lens, the eventual permanent spot turbidity affect lens clarity. More serious is the possession of Nazi health bacteria, easily keratitis infection, in view of this, has no way to promote long wear. Daily wear continuous wear for up to 14 small
When every night to remove the necessary cleaning, disinfection and proper preservation, to this day wear again. As the day wore way to clean every night to remove the lens, lens opacity is not a permanent spot. Daily cleaning and disinfection, the possibility of infectious keratitis were significantly reduced. Therefore, we must insist on wearing way, way long wear undesirable. Ordinary glasses with contact lenses do not have the advantages of solution can not solve the problems of ordinary glasses. As the contact lens and cornea close adsorption, and can rotate with the eye of the rotation, both eyes move in any direction, always light enter the eye through the lens center, eliminating the Department of ordinary spectacles produced by the edge of the prism effect and oblique astigmatism defect . Contact lenses are based on the patient surface of the cornea curvature and refraction grind, and it close to the cornea, so that the lens, corneal tear layer and formed a new refractive involved constitute a complete optical unit, lens surface curvature can be freely refractive grind. Replaced the irregular corneal surface curvature, effectively eliminate the corneal irregular astigmatism, reduced the size of the gap between the two was like. As the contact lens close to the cornea, to reduce the gap with the center of the eye, light is passed, the formation of the image on the retina and non-glasses were almost, to see things from the past will not zoom in or out. Avoid the shortcomings of ordinary glasses, the most suitable for large or monocular anisometropic eyes were not crystal. Contact lens thin and light, absorption in the corneal surface, compared to a high degree of thick and heavy glasses lenses more convenient. In addition, for some people with special needs (such as actors, athletes) a great convenience. It is precisely because so many ordinary glasses with contact lenses do not have the advantage, so its use is also more extensive than ordinary glasses.