For years, the most common frames were made from a cellulose acetate materials called zyl. Recently, new plastic material have been used for manufacture of frames. Each material has unique properties that enhance fabrication, safety, or colorization.
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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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