A lot of people develop problems with reading small print and seeing close objects during their 40s. This is called presbyopia. Fortunately, this doesn't mean that those who already have glasses to tend to their problems with nearsightedness are required to carry around two pairs of glasses. This is because of multifocal lenses, which help you with both problems, making sure you always see well.
Multifocals are a vast improvement on bifocals. Bifocals did correct problems with both near and far vision, but left everything in between a little blurred. In an effort to create a better product, progressive lenses were developed, which give you and intermediate or transition region allowing your eyes to focus on the area between near and far distances. But what creates this effect? Progressive lenses feature a subtle curvature, unlike a bifocal lens, which is sharply divided. For this reason, progressive lenses are also called no-line lenses. This makes for not just better vision at near and far distances, but also good transitions in between.
But, it can take some time to adjust to no-line lenses. Even though the gentle transition of progressive lenses is more elegant, the focal areas are relatively small because the transitional areas also take up space.
Even though multifocal lenses (or trifocals) are for presbyopia, bifocals are often used to treat children or adolescents with eye problems like eye teaming, or being unable to focus while reading, which causes headaches.
It's also important to get fitted properly, and avoid store-bought bifocals. A lot of these ''ready-made'' glasses have the same prescription in both lenses, which will not help a lot of people.
Glasses that aren't properly customized to you can lead to headaches, eye strain or even nausea. Unfortunately, presbyopia is a reality of aging. But don't forget; multifocal lenses can make all the difference.