Eyeglasses have existed since ancient time. In the ancient time, the technology is not modern and people cannot customize their lenses with protective coatings. Nowadays, there are a wide range of eyeglasses to suit all types of vision problems. Different types of lenses are produced including single vision, spherical, trifocal, and bifocal lenses. Single vision lens offers the one vision correction for the eyes. Aspheric lens is suitable for people with high prescriptions. Aspheric lens is flatter than the periphery of the lens. Aspheric lens is able to eliminate the aberrations that occur in ordinary lens. As a result, it enables the person to view things in a wider range. Aspheric lens can help the person to achieve clearer vision compare to ordinary lens. It can be used to make cosmetic eyeglasses because it reduces the magnification of the eye.
Spherical lenses have front curves. It can be used to offer correction for prescription with Rx specification. If the power is convergent, the lens has a convex shape and is used to correct hyperopic problem. If the power is divergent, the concave lens will be used to offer correction for myopia problem. Lens that has piano rx offer curves on the front and back.
Bifocal lens has two segments that are used to correct the vision. The upper portion of the lens is used to correct the distance vision. The lower portion of the lens is used to correct the near vision. The shape of bifocal lens varies.
Trifocal lens has three zones. The third zone is located on top of the bifocal zone. Trifocal lenses are available in different widths including 28, 35, and 45 mm.
The most convenient way to buy eyeglasses is to visit the online store. While at the online store, you have to choose an eyeglasses frame. Eyeglass frames can be fabricated from two types of materials including plastic and metal. Certain types of metal frames can cause skin allergy problems. If you suffer from skin allergy, you should choose hypoallergenic metal frame such as titanium frame. Stainless steel frame is also a hypoallergenic frame. If your kid is going to wear the eyeglasses, you should buy an eyeglass frame that is made from an extra tough plastic. Polycarbonate plastic frame is an extra tough frame that is durable and won't become damaged when subjected to a high amount of pressure. Some frames are equipped with spring hinges. Spring hinges enable the frame to become flexible so that it won't become damaged easily.