At past, if people want prescription glasses for both distance and reading use, they always need to prepare two pairs of glasses along with them and switch them under different circumstances. Nowadays, the appearance of multi-focal lenses have solved this problem for us and progressive lenses has become the most widely purchased lenses in recent years.
Progressive lenses which is also called progressive addition lenses (PAL) include three fields of vision, without lines, and are sometimes referred to as no-line bifocals. The top portion of the lens corrects for distance-vision, narrowing to the lower middle for mid-range, finally to the bottom portion for the near-vision or reading. The three vision fields for progressive prescription glasses are gradient increasing. The gradient usually starts at a minimum or no addition power at the top then reaches to a maximum addition power at the bottom of the lens for your prescription glasses.
Compared with bifocal or trifocal prescription glasses, progressive lenses provide a more natural correction. Instead of providing just two or three lens powers like bifocals or trifocals, progressive lenses are true “multifocal” lenses that provide a seamless progression of many lens powers for all viewing distances.
The other advantage for progressive prescription glasses is that people can easily get adapted to such lenses. With conventional bifocals and trifocals prescription glasses, images seem to “jump” sharply between the top and bottom parts of the lens. But the middle-range of the progressive lenses makes your change focus from distance to near more comfortably.
With one pair of prescription progressive glasses at hand, you can see clearly both for far distance and near work such as reading. And you can also look ahead to view your computer in the intermediate zone and drop your gaze downward to read and do fine work comfortably.
When choosing frame for the prescription progressive glasses, you are advised to choose frames with the higher lens height. Since if the frame you choose is too small, the reading portion of the lens would sometimes reduce a lot which will cause discomfort to you after the lens was cut and inserted to the frame.
The lenses for progressive prescription glasses are also available in a wide variety of materials, including regular plastic and glass, polycarbonate, high-index and photochromic lenses. You may choose them for your prescription progressive glasses according to your demand and preference.