CPO Lensometry and Spectacle Lens Verification

Question 1

What instrument is used to verify the optical power of a finished spectacle lens?

Accepted Answer

Lensometer (lensmeter)

Answer

Keratometer

Answer

Autorefractor

Answer

Phoropter

Question 2

On a manual lensometer, focusing the sphere mire target gives you:

Accepted Answer

The sphere power

Answer

The cylinder power

Answer

The axis of the lens

Answer

The prism amount

Question 3

On a manual lensometer with crossed-line mires, when one set of lines focuses sharply but the other does not at the same drum setting, this indicates:

Accepted Answer

A toric (spherocylindrical) lens

Answer

A spherical lens with no cylinder

Answer

A lens with prism only

Answer

A defective lensometer

Question 4

By ANSI/ISO convention, the axis of a cylindrical spectacle lens is measured:

Accepted Answer

1° to 180° counterclockwise

Answer

0° to 360° clockwise

Answer

0° to 180° clockwise

Answer

1° to 360° counterclockwise

Question 5

Before measuring any lens on a lensometer, the first step the technician should perform is:

Accepted Answer

Zero-calibrate the lensometer eyepiece and power drum

Answer

Apply ink dots to the lens surface

Answer

Measure the bifocal add power first

Answer

Remove the lens from the spectacle frame

Question 6

Ink dots placed on a spectacle lens during lensometry serve to mark:

Accepted Answer

The optical center and prism reference point for alignment

Answer

The cylinder axis location only

Answer

The bifocal segment top edge

Answer

The location of the anti-reflective coating

Question 7

When calibrating a manual lensometer with no lens in place, the power drum should read:

Accepted Answer

0.00 D (plano)

Answer

+0.25 D to account for instrument error

Answer

-0.25 D as a standard offset

Answer

Whatever the last measured lens read