Practice Quiz

ABO NOCE Basic Opticianry

Category - Ophthalmic Optics

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On a lensometer, how do you determine the center of a prescription lens?
  1. You first measure the lens width and divide it in half
  2. You determine the center of the mires with both sphere and cylinder power
  3. You determine with either sphere or cylinder, not both
Explanation
Answer: B - To determine the center of a prescription lens in a lensometer you must center the mires with both sphere and cylinder power.

You must find out if the lens has cylinder power in addition to sphere power and mark with the lens marker. You can adjust to mark the lens by adjusting the height of the reticle on which the lens is sitting.
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