| By :
William Gabriel
Both bifocal and multifocal contact lenses were designed specifically for people who are suffering from presbyopia. Both options have proven to carry specific benefits and drawbacks and without understanding what each of these options actually provide, making a decision can be difficult. Fortunately, the differences are easy to understand once you realize what they are and the specific contact lenses work. Here is a closer look at the differences between bifocal and multifocal contact lenses. The most fundamental difference is that bifocal contact lenses have two prescriptions within the same lens. Multifocal contact lenses carry a range of different powers in each lens, which is similar to a progressive lens that is used in glasses. It is important to use this differentiation, because some people will use "multifocal" as a catch-all that includes any lens that has more than one power (including bifocals). Overall there are 2 basic designs for lenses that treat presbyopia: Alternating and Simultaneous. The alternating vision design forces your pupil to alternate between two different powers by changing your gaze upwards or downwards. This design is specifically used for bifocal contact lenses, however there have been some trifocal lenses that have tried applying this same strategy. If you are having problems imagining how this type of lens works, take a moment and picture a traditional pair of bifocal glasses. Those lenses function the same way that the alternating design bifocal contact lenses do. The reason that some people feel that this option is the best is because you are in total control of which power you are using. These types of contacts are normally smaller than traditional soft contact lenses and instead of moving with your eyes, they stay fairly stationary. This allows your eye to easily move from one power to another. There are two different types of simultaneous designs for presbyopia. The first is the concentric ring design. The concentric ring design is primarily for bifocal contact lenses. With this design, there are two rings of different powers that lie within your pupil area. The center can be either near or far vision powered and the decision is normally up to you. To best imagine this type of design, try to imagine a dartboard. Now imagine that each ring alternates between near and far vision. The other type of design is the aspheric multifocal design. These contact lenses work the same way that progressive eyeglass lenses work. There are a range of different powers that are all spread out and blended across each lens. While this has proven to be extremely effective, it is important to note that it will take some time for your brain to learn to choose the correct prescription level for any given moment. Because of the vast array of options that you have to choose from, trying to decide between bifocal and multifocal contact lenses can be a difficult one. Many people suggest that the best idea is to test out a variety of different options until you find the right fit for your specific needs and comfort. As contact lenses continue to become the more popular option, there will continue to be improvements in regards to creating and improving additional multifocal solutions.
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