Prescription eyeglasses are glasses that have been prescribed by an optometrist to be used by someone who has been diagnosed with an eye condition. Depending on the condition, a different lens will be prescribed. Prescription eyeglasses are broken down into four different categories. Single vision lens has the same power to coordinate the top of the lens to the bottom of the lens. People who have been diagnosed as farsighted or nearsighted with astigmatism may have wear single vision glasses to correct these types of eye disorders. Astigmatism is a condition which does not reflect light in the retina, thus causing distorted images. A Bifocal lens is used to correct a condition called presbyopia. This disorder usually occurs in people in their 40s in the afternoon. If a person has been diagnosed with Presbyopia can not focus on close objects. That's where Bifocal lens is useful. The top of the lens is used for far vision and the bottom of the lens is useful in close vision. Presbyopia people need both types of centers view on prescription eyeglasses. The Trifocal Lens-which means they have three centers of views-is designed similar to bifocals, except the center focal point of the lens for intermediate vision. The fourth type of lens is the multi-focal lens. It has more than one focal view, so a Bifocal and Trifocal lenses are several types of focus. Other types of lenses that are specially designed for other purposes include the team's goal. They are designed so that when sitting in front of a computer, a person can see the monitor nest documents simultaneously monitor. And then there are double bifocals, which rarely prescribed, but when it's usually for pilots, electricians or other professions that have need for close vision overhead.
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