What Do Contact Lens Numbers Mean?
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Function
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A contact lens prescription is usually assigned by an optometrist or an ophthalmologist. After your vision is checked by an eye doctor, he will write a prescription using medical measurements and terms. This prescription determines the size and power of the lenses.
Significance
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The numbers that appear on the side of contact lens boxes, next to symbols, are measurements that determine the size of the lenses.
What are symbols?
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Some symbols used in lens prescriptions are OD, which stands for Right Eye; OS, which stands for Left Eye; OU, which stands for Both Eyes; BC, which stands for Base Curve; and Dia, which is short for Diameter.
Types
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There are different types of lenses. If you were prescribed toric lenses then there would be two additional columns: cylinder and axis. Toric lenses are prescribed for people with astigmatism.
Fun Fact
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A contact lens prescription is different from your eyeglass prescription. This is because contact lenses sit on the surface of the eye, while eyeglasses are 12 mm away from the eye.
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