Some people have a condition that is called presbyopia. When it happens, you, while reading, need your materials to be farther from your eyes like you read a newspaper or menu, and then you can see it clearly. To give good vision to people who have this condition bifocal contact lenses are designed. Usually, presbyopia begins at around age 40. If you are presbyopic, no matter what your age, you are a potential candidate for bifocal contact lenses.
You can choose what material of contacts is suitable for you: soft or rigid gas permeable materials. Today's bifocal contact lenses are even available in a disposable or frequent replacement wear regimen. That means you can change used lenses at specified intervals with fresh, new lenses. Disposable bifocal contact lenses first appear in 1999. Now daily disposable bifocal contact lenses are available; you take them off nightly and replace with a brand-new pair the next morning.
 Bifocal contacts work like bifocal eyeglasses:
1. They have two powers on one lens: one is used to correct distance vision, if that is needed, and the other - to correct near vision.
2. Some contact lens combines two prescriptions, with the distance vision on the top of the lens and the near vision at the bottom, like a bifocal eyeglass with a line separating the powers. Other works similar to progressive eyeglass lenses, where on different parts of the lens the different prescriptive powers are blended. In this way your eyes learn to differentiate the proper power for the correct distance.
Not every one can war the bifocal contact lenses. Because it takes some time to adjust to the lenses, as the eye needs time to adjust to sort out the different powers. The time it takes will depend on every particular person. Likewise, some people won’t be satisfied with the current variety of bifocal contacts.
There are two main types of bifocal contact lenses:
• Segmented (which is also called alternating or translating): These resemble standard bifocal eyeglasses have two distinct segments, or areas, of the lens. You have to look through particular different part of the lens for distance vision (upper) and near vision (lower), and the lenses can move, making vision inconsistent. Sometimes, the lenses may be weighted for being kept properly oriented on your eye.
• Concentric or simultaneous: Correction for near or distance vision is concentrated in the center of the lens, and correction for the other type of vision - around the center. Usually there is a sharp boundary between these two areas. Aspheric, a special type of concentric lens, makes the boundary between areas for near and distance vision not so sharp and provides a gradual transition between them. This helps to provide a way for vision correction at intermediate distances. Accordingly concentric or simultaneous contact lens corrects both near and distance vision close to the center of the lens, and at the same time both near and far objects can be in focus. An image of either near or distant objects is formed from the visual information, which your brain learns to select. That’s why some adjustment is required for simultaneous bifocal contact lenses.
Not everyone is satisfied with bifocal contact lenses. Some people have difficulties as to adjusting to the different areas for near and distance vision, or the quality of the vision correction provided by the lenses can be unsatisfied. Some current designs for bifocal lenses cannot correct some vision problems properly .
Also, because of complexity, bifocal contact lenses require more time for fitting process. Besides such contacts are usually more expensive than single-vision ones.
Bifocal contact lenses require no more efforts to care than regular contacts, and it’s very easy to insert and remove them from the eye. You can go all day long without needing to think about your contacts. If you wear bifocal or progressive eyeglasses, however, you constantly feel the weight of your glasses on your nose, you must take them off sometimes to clean, and have to put up with fogging on cold days. You also need to remove and replace reading glasses several times a day, too, and that’s why you can easily misplace or scratch them.
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