NOCE Optical Instrumentation Use 2

Question 1

When using a lensometer to measure a bifocal add power, where should the bifocal segment be positioned in the instrument?

Accepted Answer

The reading segment is placed in the aperture ring

Answer

To measure add power, the reading (near) segment is placed in the lensometer aperture ring to read the near prescription.

Question 2

A keratometer reading shows 44.00 D @ 180 and 46.50 D @ 090. What is the corneal cylinder?

Accepted Answer

2.50 D

Answer

Corneal cylinder is the difference between the two principal meridian readings: 46.50 - 44.00 = 2.50 D.

Question 3

Which instrument is used to measure the interpupillary distance (PD) electronically and digitally?

Accepted Answer

Pupillometer

Answer

A pupillometer is the instrument specifically designed to measure interpupillary distance, often digitally.

Question 4

When neutralizing a lens with a lensometer, the power wheel is adjusted until the target mires are sharp and at the center. What does this indicate?

Accepted Answer

The sphere power has been measured

Answer

When the target is centered and clear with the power drum adjusted, the sphere power (or one principal meridian) of the lens has been neutralized.

Question 5

A radiuscope is primarily used to measure which property of a contact lens?

Accepted Answer

Base curve radius

Answer

The radiuscope measures the base curve (back central radius) of rigid contact lenses.

NOCE - National Opticianry Competency Examination Practice Test