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Materials and functions of eyeglasses lenses

Eyeglass lens materials

• 1. Glass: glass is the most traditional material used to produce eyeglass lenses. This material is probably closely linked with the origin of the name "glasses". However, this material is very rarely utilized by modern eyewear manufacturers, because of its intolerable drawbacks. Glass lenses are too heavy in weight and fragile. And glass lenses with a strong prescription are extremely thick.
• 2. Regular plastics: regular plastic lenses are made from a cast molding process during which a liquid plastic material is baked for a long period. These lenses are lighter than glass lenses but they still come with an unusual thickness once there is a severe vision condition.
• 3. High index plastics: High-index lenses with a strong prescription can be as thin as regular lenses. They are especially suitable for modern plastic and metal frames with rims thinner than the lenses. High-index eyeglasses lenses are also lighter than regular plastic lenses.
• 4. Polycarbonate: this is definitely the standard material used to make eyeglass lenses for safety glasses and children's eyeglasses. Polycarbonate lenses feature lightness, UV protection, thinness and impact-resistance.

Eyeglasses lens functions

Non-prescription or Plano lenses:
These lenses are not for vision correction. Regular sunwear lenses and protective lenses belong to this category. Some people even resort to these lenses solely for eye beauty.

• 1. Single-vision lenses: having only one focal point, single-vision lenses can address only one vision problem. Myopia glasses, hyperopia glasses and presbyopia glasses or reading glasses all take use of single-vision lenses. These lenses serve a majority of young and middle-age eyewear users.
• 2. Bifocal lenses: according to a similar definition of single-vision lenses, a bifocal lens has two focal points, respectively correcting two different vision problems. Presbyopia is always included. The other one can be myopia or hyperopia. In most cases, distance vision can be perceived through the top section of the lens and close vision the bottom section.
• 3. Trifocal lenses: by extending bifocal lenses with an intermediate vision zone, trifocal lenses are available. Typically, an intermediate section will be inserted between the distance and close vision sections. While the other two parts are for distance and close vision, the middle part is for computer vision or for a smoother transition. This extra lens section enables regular PC users to relieve from eye strain and stress.
• 4. Progressive lenses: like bifocals and trifocals, progressive lenses also belong to multifocal lenses. The most significant difference lies in that a progressive lens has a couple of focal points. By incorporating a gradually increasing powers gradient, progressive lenses can offer clear vision aid at all distances, ranging from distance, intermediate to close-up.

Eyeglasses lens colors

For Plano glasses, tints are applied onto them just for extra decoration. Some people resort to these lens colors for facial beauty enhancement. Feasible tints contain green, orange, rose, pink, yellow and gray, etc. Lens tints can also be applied to prescription eyeglasses.

Eyeglasses lens coatings:

• 1Anti-fog coating: regular eyeglass lenses will fog up when the wearer enters an indoor environment from the outside in the winter time. Anti-fog coating applied to ordinary lenses helps prevent this bothersome condition.
• 2Anti-reflective coating: this coating helps prevent light reflection on both the front and back sides of the lenses.
• 3Scratch-resistant coating: as the name indicates, this coating protects regular eyeglasses lenses against accidental scratches.