A lot of people begin to notice problems with reading small print and seeing close objects during their 40s. This condition is called presbyopia. If you already wear glasses for distance vision, and develop presbyopia, you won't need to start carrying and switching between two pairs of glasses. This is all thanks to multifocal lenses, which correct both problems, ensuring that you always see well.
Before mulifocals, bifocals were the popular fix, but they have a significant disadvantage; while they correct problems with both near and distant objects, middle distance is blurred. In an effort to create something more helpful, progressive lenses were made, which give you a transition region allowing your eyes to focus on distances that are in the middle. Progressive or no-line lenses are a type of multifocal lens that have a gradual curvature across the lens surface instead of an obvious and harsh line separating the two areas of the lens. This creates not just clearer vision at near and far distances, but also good transitions between the two.
These lenses, although better, may take a small period of time to adjust to. Even though the gentle lens curve results in a product that is elegant, the focal areas are quite small because more lens space is used for the transitional areas.
Bifocals are still used though; they are used to treat kids and teenagers who have a hard time focusing when reading.
Even though it may seem like an easy fix, it's best to steer clear of drug store bifocals. Most of these ''ready-made'' glasses are one-size-fits-all, which means that the prescription is the same in both lenses and are not customized for the wearer.
Glasses that aren't properly customized to you can lead to eye strain, discomfort and headaches. Unfortunately, presbyopia is a reality of aging. But keep in mind that multifocal lenses can make all the difference.