The optical power of a lens is measured diopters. Diopter is defined as the reciprocal of the focal length in meters. The greater the optical power, the shorter the focal length. The focal length of a plus lens will be the same as focal length of a minus lens with the same power.
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Advantages: The chart is familiar Inexpensive, quick and easy to use and interpret Disadvantages: Snellen chart has only one 6/60 lette...
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Preferences: Similarly quantities of letters per line. Consistently separating amongst lines and letters. Uniform movement ...
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Don't take your eyes for granted. Take these easy steps to keep your peepers healthy.
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