Optical Instrumentation Use Questions and Answers Flashcards
7 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Optical Instrumentation Use Questions and Answers flashcards as text
When using a lensometer to measure a bifocal lens, where should the segment optical center be placed to read the add power?
Answer: Over the near segment optical center
The near segment optical center must be placed over the lensometer stop to accurately measure the add power.
Which instrument is used to measure the curvature of the front and back surfaces of a contact lens?
Answer: Radiuscope
The radiuscope (also called an ophthalmometer for contact lenses) measures the base curve radius of contact lenses.
On a manual lensometer, the power drum is turned until the target lines are sharpest. What does a clear sphere target with blurred lines indicate?
Answer: There is cylinder power present
When the sphere lines are clear but cylinder lines remain blurred, cylinder power exists in the lens and needs to be neutralized.
A lensometer reading shows that the target does not center in the eyepiece even when the lens is moved horizontally. This indicates the presence of:
Answer: Prism
Prism causes the target to be displaced from center, and the amount of displacement indicates the prismatic power.
What is the purpose of the ink dots placed on a lens after neutralization with a lensometer?
Answer: To mark the optical center and axis
The three ink dots mark the optical center and cylinder axis orientation so the lens can be properly edged and positioned in the frame.
When measuring progressive addition lenses (PALs) with a lensometer, the distance power is measured:
Answer: Through the distance zone in the upper portion
The distance power of a PAL is measured through the upper distance zone, where the prescribed distance Rx is located.
A Geneva lens clock (lens gauge) measures:
Answer: The surface curvature of a lens in diopters
A Geneva lens clock measures the surface curvature of a lens by converting the sag height to approximate diopter values.