CPO Lensometry and Spectacle Lens Verification 3

Question 1

The optical center of a spectacle lens is the point where:

Accepted Answer

Light passes through without any prismatic deviation

Answer

The bifocal segment begins

Answer

The cylinder axis intersects the sphere meridian

Answer

The anti-reflective coating is applied most densely

Question 2

The power drum on a manual lensometer is calibrated in which unit?

Accepted Answer

Diopters (D)

Answer

Millimeters of focal length

Answer

Prism diopters (Δ)

Answer

Degrees of arc

Question 3

When performing lensometry on a tinted (sunglass) spectacle lens, the recommended approach is to:

Accepted Answer

Increase the lensometer's illumination intensity and proceed normally

Answer

Measure only the clearest, least tinted area of the lens

Answer

Remove the tint with solvent before measurement

Answer

Document that measurement is not possible on tinted lenses

Question 4

According to ANSI Z80.1 standards, the acceptable tolerance for add power in a finished bifocal spectacle lens is:

Accepted Answer

±0.12 D

Answer

±0.25 D

Answer

±0.50 D

Answer

±0.06 D

Question 5

A patient's prescription includes 2Δ base-out for each eye. When verifying with the lensometer, you would expect the mire target to be displaced:

Accepted Answer

Toward the nasal (inner) edge of each lens

Answer

Toward the temporal (outer) edge of each lens

Answer

Superiorly in each lens

Answer

Inferiorly in each lens

Question 6

The vernier scale on a manual lensometer axis wheel allows the technician to read the cylinder axis to the nearest:

Accepted Answer

1 degree

Answer

5 degrees

Answer

10 degrees

Answer

0.5 degrees

Question 7

When documenting lensometry findings for a finished pair of spectacles, the technician should record findings as:

Accepted Answer

Separate sphere, cylinder, and axis values for each eye, with any prism noted

Answer

A single combined power for convenience

Answer

Only the cylinder power since sphere is assumed plano unless stated

Answer

The net spherical equivalent for each eye