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 optical center is the specific point on a lens through which light travels in a straight line without being deflected by prism.

Question 2

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

Accepted Answer

Diopters (D)

Answer

The lensometer power drum is calibrated directly in diopters, allowing the technician to read lens power without conversion.

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

Increasing the lensometer's internal illumination compensates for light absorbed by the tint, allowing the mires to remain visible for accurate measurement.

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

ANSI Z80.1 specifies a tolerance of ±0.12 D for add power; a discrepancy greater than this requires the lenses to be returned to the laboratory for remake.

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

Base-out prism has its base (thick edge) toward the temporal side, causing the mire target to appear displaced toward the nasal side — opposite the base direction.

(CPO) Certified Paraoptometric Practice Test

(CPO) Certified Paraoptometric Practice Test

CPO Lensometry and Spectacle Lens Verification 3