ABO NOCE Basic Opticianry Optical Instrumentation Use Questions and Answers 4

Question 1

Which instrument is used to measure the vertex distance between the back surface of a spectacle lens and the front of the cornea?

Accepted Answer

Distometer (vertex distance gauge)

Answer

A distometer (vertex distance gauge) measures the distance from the posterior lens surface to the anterior cornea, important for high-power prescriptions.

Question 2

A lensometer target appears as two sets of lines oriented 90 degrees apart. The lines running in one direction clear at +2.00 and those running perpendicular clear at +3.50. What is the prescription?

Accepted Answer

+2.00 +1.50 × axis of first clear lines

Answer

Starting with the lower power meridian (+2.00) as the sphere, the cylinder is the algebraic difference (+1.50), and the axis aligns with the first set of lines to clear.

Question 3

What does a seg height measurement represent in opticianry?

Accepted Answer

The distance from the bottom of the frame to the pupil center

Answer

Seg height is measured from the lowest point of the finished frame to the center of the patient's pupil, determining where the bifocal segment should be placed.

Question 4

When measuring a plano lens on a lensometer, the target should be:

Accepted Answer

Centered and clear when the drum is at zero

Answer

A plano (no power) lens does not alter the light path, so the target remains centered and clear when the power drum is set to zero.

Question 5

The 'mire' in a keratometer refers to:

Accepted Answer

The illuminated target pattern projected onto the cornea

Answer

Mires are the specific illuminated rings or crosses projected onto the cornea whose reflected images are measured to calculate corneal curvature.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Optical Instrumentation Use Questions and Answers 4