Essay example --

A lens is an optical device that transmits or refracts light. Eyeglass lenses are glass or plastic items that are placed inside eyewear frames in order to correct the wearer’s vision. More than 80 percent of all eyeglasses worn today are plastic lenses. The glass lenses were popular in the 1945 until the plastic lens was introduced in 1952. Convex and concave lenses are known as spherical lenses. Convex lenses were the first lenses used to correct vision problems. They are used to correct hyperopia (farsighted vision). These lenses are thicker in the middle than at the edges. Concave lenses are used to correct nearsightedness. This is a condition that makes people see things that are close to them but struggle to see things far away. Concave lenses are curved inward like the inside of a spoon. Whether you have plastic or glass, concave lenses or convex lenses they are produced in much of the same way. Years ago opticians relied on separate optical laboratories to produce eyeglass lenses. However today optical outlets receive lens â€Å"blanks† (blanks received from optical laboratories) which are plastic pieces already formed to fit exactly into the front of the lens. The stages are grinding, polishing, and shaping. Materials used are plastic or glass blanks, which are thick in size to eyeglass frames, though slightly larger. Thickness may vary depending upon the prescription. Other raw materials used to make eyeglass lenses are adhesive tape, a liquid with a lead alloy base, metal, and dyes and tints. Eyeglass lenses are designed in many shapes in order to match the eyeglass frame. Assuming that plastic lenses are being made at an optical laboratory technician’s input optical prescription for a pair of lenses i... ... may also verify optics and optical prescription in the lensometer. The manufacturing of lens has progressed over the years. The labor-intensive nature of making glasses has made it hard for U.S. companies to make high-precision lenses to compete with forms located in countries with low labor costs. However the manufacturing process has become more automated which makes the process more capital intensive rather than labor intensive. American companies are able to compete on even ground. Now there is computer assisted grinding process using the Opticam. This machine is capable of surfacing, edging, and centering in one setup, which save so much time. Whether you use the old-fashioned labor-intensive approach or use newly developed technology it is important to know that the manufacturing of lenses requires strict adherence to guidelines and quality control.