ABO NOCE Basic Opticianry Optical Instrumentation Use Questions and Answers 5

Question 1

A lens clock reading on the front surface of a lens shows +6.00 D and the back surface shows –2.00 D. Using a simplified calculation (n=1.53), the approximate lens power is:

Accepted Answer

+4.00 D

Answer

Using the lensmaker's equation simplified, the approximate power is the sum of the front and back surface powers: +6.00 + (–2.00) = +4.00 D.

Question 2

What is the purpose of the 'nose piece' or 'lens stop' on a lensometer?

Accepted Answer

It supports and positions the lens being measured at the correct distance

Answer

The lens stop holds the spectacle lens at the precise focal distance from the lensometer's collimating lens for accurate power measurement.

Question 3

Which type of lensometer reticle pattern uses a bullseye (circle with cross) target?

Accepted Answer

American Standard (ANSI) pattern

Answer

The American Standard lensometer uses a bullseye target with concentric circles and crossed lines to allow simultaneous sphere, cylinder, and prism measurement.

Question 4

During lensometer verification, a lens shows 2 prism diopters base-out in the right lens. On the lensometer, this means the target is displaced:

Accepted Answer

2 rings toward the temporal side of the reticle

Answer

Base-out prism displaces the target toward the temporal (outer) side of the reticle because prism bends light toward its base.

Question 5

A PD ruler is being used to measure a patient's binocular distance PD. The ruler should be aligned:

Accepted Answer

From the center of one pupil to the center of the other pupil

Answer

PD is the distance between the centers of the two pupils and must be measured center-to-center for accurate optical alignment.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Optical Instrumentation Use Questions and Answers 5