As we age, the lens in our eye starts to lose its elasticity, and the muscles that control the lens shape get weaker, resulting in a form of farsightedness called presbyopia. There are several other factors besides age that can accelerate the onset of presbyopia, including eye injury, diseases such as diabetes or multiple sclerosis, drug use, gender (women tend to get it at a younger age than men), and occupation (if your job requires a lot of close up work, presbyopia may occur sooner). While you may be able to control some of the risk factors, there is no known way to prevent presbyopia and it is considered part of the natural aging process. If you find yourself having to hold books and other reading material farther away from you to read it, you may be developing presbyopia and need bifocal vision correction. Contact lenses are now available for people who need bifocals and after a discussion with your eye care professional, you can decide if contact lenses are the right choice for you.
Bifocal contact lenses are available across the whole range of contact lens materials, from rigid gas permeable (RGP) lenses, to traditional soft contact lenses, to the new silicon hydrogel soft contact lenses, which allow much more oxygen to reach the eye. They are also available across the spectrum of wear schedules, from the RGPs which can last several years, to daily disposables.
The location of the distance and near correction in bifocal contact lenses varies with style. Some, called aspheric, have near and distance correction dispersed around the contact lens, and the eye will learn to use the part it needs at the correct time without you being aware of it. In others, called concentric, one type of correction is found in the middle of the contact lens, while the other kind of correction encircles it around the outside of the lens. Translating lenses work much like bifocal glasses, with one type of correction on the top, and the other on the bottom. Another option for people with presbyopia is to have the different corrections in different eyes, called monovision. In other words, in one eye you would wear a prescription to correct nearsightedness, and in the other, you would wear on to correct farsightedness. You will probably not even notice the difference, and because the lenses are less specialized, it may be more economical to purchase contact lenses this way if it is a style that works for you.
