ABO NOCE Basic Opticianry Optical Instrumentation Use Questions and Answers 2

Question 1

When using a lensometer to measure a bifocal lens, where should the segment optical center be placed to read the add power?

Accepted Answer

Over the near segment optical center

Answer

The near segment optical center must be placed over the lensometer stop to accurately measure the add power.

Question 2

Which instrument is used to measure the curvature of the front and back surfaces of a contact lens?

Accepted Answer

Radiuscope

Answer

The radiuscope (also called an ophthalmometer for contact lenses) measures the base curve radius of contact lenses.

Question 3

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?

Accepted Answer

There is cylinder power present

Answer

When the sphere lines are clear but cylinder lines remain blurred, cylinder power exists in the lens and needs to be neutralized.

Question 4

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:

Accepted Answer

Prism

Answer

Prism causes the target to be displaced from center, and the amount of displacement indicates the prismatic power.

Question 5

What is the purpose of the ink dots placed on a lens after neutralization with a lensometer?

Accepted Answer

To mark the optical center and axis

Answer

The three ink dots mark the optical center and cylinder axis orientation so the lens can be properly edged and positioned in the frame.

ABO NOCE Basic Opticianry Practice Test