Progressive lenses, sometimes referred to as "no-line" bifocals, provide vision correction for the three basic vision zones - distance vision, intermediate vision, and near vision. Because they provide vision in these three zones, they are often thought of as a type of trifocal.
In reality, progressive lenses are neither a type of bifocal or trifocal - they are "aspheric" in design, which means the curvature (and focusing power) gradually changes from the top of the lens to the bottom. It is this gradual change or "progression" in power from top to bottom that gives rise to the name "progressive."
Progressive lenses provide a great solution for many people who find their present lens design limits their vision for a particular distance or activity. Progressives offer a range of vision as close to natural as can be obtained from prescription eyeglasses. They provide clearer vision not just for distance, intermediate and near but also for all distances in between. Because there is no abrupt change of power in the lens, there are no visible dividing lines.
The distance zone of the lens allows you to see objects from a few feet away to as far as your eye can see. The mid-range portion of the lens ("progression corridor") allows you to clearly see anything at an arm's length, such as your computer screen, objects on your desk, or items on a shelf at the supermarket. The lowest part of the lens, the near zone, allows you to see up close. The design of progressive lenses also allows a more natural and relaxed head posture when viewing objects at slightly longer reading distances, such as a newspaper or computer screen.
More Options - A variety of progressive lens designs are available today. Some progressives are designed with a wider intermediate zone to work especially well for computer use. Others have a larger reading zone. In the past, a larger frame was often required when selecting progressive lenses. If a frame was too small, a large portion of the near zone was removed when cutting the lens to fit the frame. Many lens manufacturers now offer "compact" progressive designs that work very well with smaller frames. Progressives are available in glass, plastic, polycarbonate, and photochromic (light-sensitive) lenses.
Modern progressive lenses offer outstanding clarity and comfort for seeing at all distances. Modern designs also make the adaptation process much easier than in the past. if you've tried progressives before, realize that much has changed in both lens design and materials. The next time you update your glasses, be sure to ask if progressive lenses might be right for you.