Presbyopia, or farsightedness caused by reduced elasticity of the eye’s lens, affects nearly everyone older than 65.
About 42 percent of Americans who are in their prime are nearsighted. For them, a simple pair of reading glasses can’t solve the problem of presbyopia, and that’s where bifocals, trifocals, and progressive lenses come in.
Options For Correcting Presbyopia
Bifocals are simply glasses with lenses that have one area that corrects nearsightedness and a smaller area in the lower half that corrects farsightedness. As presbyopia worsens, middle distances can also become difficult to focus on. This can be corrected by trifocals, which add a strip in between the two prescriptions in bifocals, allowing wearers to see things like their computer screens better.
The trouble with bifocals and especially trifocals is that the lines between the different sections of the lens are difficult for the wearer to ignore, causing a jarring “image jump” effect, and they also serve as a giveaway to other people that they’re getting older. Fortunately, people who are nearsighted and dealing with presbyopia have another option that doesn’t have these drawbacks, and that’s progressive lenses.
How Progressive Lenses Work
So how do progressive lenses do the same job as bifocals or trifocals without those pesky lines? Unlike bifocals and trifocals, which are multiple lenses combined into one, a progressive lens is a single lens. The prescription gradually changes along a corridor of power from distance vision at the top to middle vision in the center to near vision at the bottom. This allows wearers to see at all distances, depending on how they tilt their heads.
There is a tradeoff to make this complex lens design possible, which is that anything seen through the bottom corners of a progressive lens will look blurred. However, newer designs and technology are helping to reduce this flaw. In addition, when we examine patients for these lenses, we take measurements of the eyes and frames so we can put that corridor of power in the exact location it needs to be so they can see normally.