CPO Lensometry and Spectacle Lens Verification 2

Question 1

To determine the add power of a flat-top bifocal lens, a technician should:

Accepted Answer

Subtract the distance power reading from the near segment power reading

Answer

Add power is calculated by measuring the power through the near segment and subtracting the previously measured distance power; the difference equals the addition.

Question 2

Prismatic power in a spectacle lens is measured in which unit?

Accepted Answer

Prism diopters (Δ)

Answer

Prism power is expressed in prism diopters (Δ), where 1Δ displaces light by 1 cm at 1 meter.

Question 3

When the lensometer target mire appears displaced from the center of the reticle, this indicates:

Accepted Answer

Prismatic power is present in the lens

Answer

Displacement of the mire target from the optical center of the lensometer reticle indicates prismatic power; the direction and amount of displacement identify the prism base and magnitude.

Question 4

For a progressive addition lens (PAL), where should the lensometer be positioned to measure the distance power?

Accepted Answer

Through the distance zone in the upper portion of the lens

Answer

The distance power of a PAL must be measured through the distance optical zone located in the upper portion of the lens.

Question 5

A lens prescription reads -1.00 -0.50 x 180. When transposed to plus cylinder form, it becomes:

Accepted Answer

-1.50 +0.50 x 090

Answer

Transposing -1.00 -0.50 x 180: new sphere = -1.00 + (-0.50) = -1.50; new cylinder = +0.50; new axis = 180 − 90 = 090. Result: -1.50 +0.50 x 090.

(CPO) Certified Paraoptometric Practice Test

(CPO) Certified Paraoptometric Practice Test

CPO Lensometry and Spectacle Lens Verification 2