Practice Quiz

Ophthalmic Technician

Category - Lensometry and Spectacle Skills

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When the ground-in prism in a spectacle is of very high power, it is difficult to locate the center of the target. What can be added to overcome the difficulty and to determine the amount of prism in the lens?
  1. Convex lens
  2. Concave lens
  3. Hand-held lens
  4. Cylindrical lens
Explanation
Answer: C - When the ground-in prism in a spectacle is of very high power, it is difficult to locate the center of the target. Hand-held prisms are added to center the target and to determine the amount of prism in the lens. The prism induced by each lens must be calculated separately.
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