Ophthalmic lenses are available in variety of style. In the simplest of forms, lens styles are available in Single Vision and Multifocal powers.
Single Vision lenses have the same focal power throughout (top to bottom) and can be used to correct nearsightedness, farsightedness, astigmatism, or a combination of these disorders. Most people who wear glasses before the age of 40 have single vision lenses.
Multifocal lenses allow you to focus through different prescriptions for different distances through the same lens: essentially, more than one point of focus, hence the term “multifocals”. With multifocal available in Bifocal& Progressive additional lens designs.
Bifocals – meaning a lens with two points of focus, usually one for distance and one for near. A small portion of the bifocal eyeglass lens is reserved for the near-vision correction. The rest of the lens is usually a distance correction, but sometimes has no correction at all in it, if you have good distance vision. Generally, you look up and through the distance portion of the lens when focusing on points farther away and look down and through the bifocal segment of the lens when focusing on reading material or detail work up to about 18 inches away.
Progressive lenses, sometimes referred to as no-line bifocals, not only provide visual correction for various distances that traditional bifocals can’t, but they also hide the fact that you even need reading glasses.
Progressive lenses are the closest to how natural vision is that you can get in a pair of prescription eyeglasses. They are more than just a defined near and distance correction in one lens. Rather, progressives provide a smooth transition from distance through intermediate to near, with all the in-between corrections included as well. This constant graduation of the prescription means that you can look up to see in the distance, look ahead to view things such as the computer in the intermediate zone, and drop your gaze downward to read and do fine work comfortably close up.
Design of Progressive lens – no line bifocal, provide the wearer with
distance, intermediate & near viewing without visible “segment”
showing on the lens.