Progressive Lenses - Everything You Need To Know
In the past, bifocal lenses were used to correct two different eye prescriptions. Bifocals were easy to spot - they had a line dividing the lens in two, with the upper half for distance vision, and the lower half for reading. For many people, these were considered ugly and even inconvenient, as wearers would suffer from “image jump” when their focus flickered above and below the clearly-defined boundary of the two parts of the lens.
Advantages of progressive lenses
Modern progressive lenses, on the other hand, have a smooth and consistent gradient between differing lens powers. In this sense, they can also be called “multifocal” or “varifocal” lenses, because they offer all of the advantages of the old bi- or trifocal lenses without the inconveniences and cosmetic drawbacks. That means the top of the lens is adapted for distance vision, and gradually diminishes in power towards the bottom, which is designed for reading or other “close up” tasks, like checking a price tag or using your smartphone. This normally only requires a small adjustment in terms of eye position, as we tend to look at distant objects in the upper part of our visual field, and near objects in the lower.
The other obvious advantage of progressive lenses, for people who are used to switching between different pairs of glasses for different activities (such as reading and driving, for example), is that with one pair of progressive lenses, you eliminate the need to ever switch again! Just one pair will serve you in all your daily tasks.
Adapting to Progressives
Adapting to progressive lenses can take some time, ranging from several hours to several days. This is because the gradient power of the lens can also cause aberrations in your peripheral vision – the left and right extremes of the lens are not as strongly “progressive” as the central, vertical corridor, meaning your vision could seem blurry when looking to the sides. However, as with any developing technology, each new generation of progressive lenses represents an improvement on the last, and many people never suffer any problems at all.
The latest generation of progressive lenses are known as “free-form” lenses, which are made with a computer-aided manufacturing process to reduce aberrations. Each lens is customized exactly to the position of the wearer’s eye, taking into account the angles between each eye and the surface of the lens when looking in different directions, providing the sharpest, crispest image possible, as well as enhanced peripheral vision.