FREE ABO NOCE Basic Opticianry Lensometry & Verification Questions and Answers

Question 1

When performing lensometry on a progressive addition lens (PAL), which of the following is the correct procedure to verify the full distance prescription?

Accepted Answer

Read the power by moving the lens until the mire target is clear in the distance reference circle.

Answer

Read the power at the approximate geometric center of the lens.

Answer

Read the power at the prism reference point (PRP).

Answer

Read the power at the near reference point, then subtract the add power.

Question 2

A lensometer reading for a single vision lens shows -2.50 sphere with the mires clear and centered. What is the next step in verifying the lens, particularly regarding axis if it were a sphero-cylinder lens?

Accepted Answer

Rotate the lensometer's axis wheel until one set of mires is clear, then rotate to clear the other set.

Answer

Rotate the lens until the cylinder axis is aligned with the lensometer's axis indicator.

Answer

Verify the optical center placement using a lens marker.

Answer

The lensometer automatically determines the axis, so no further action is needed.

Question 3

You are verifying a pair of spectacles and measure a horizontal prism of 0.5Δ Base Out (BO) in the right eye and 0.5Δ Base In (BI) in the left eye. What is the total resultant horizontal prism for the patient at the pupillary distance (PD)?

Accepted Answer

1.0Δ Base Out

Answer

1.0Δ Base In

Answer

0.0Δ (neutral)

Answer

0.5Δ Base Out

Question 4

Which of the following is the primary purpose of marking the optical center(s) of a lens during verification?

Accepted Answer

To verify that the optical center aligns with the patient's pupil center for optimal vision.

Answer

To identify the lens material type.

Answer

To ensure the lens is properly oriented in the frame.

Answer

To confirm the prescribed sphere and cylinder power.

Question 5

A technician is verifying a bifocal lens. After neutralizing the distance portion, what is the next step to accurately measure the add power?

Accepted Answer

Measure the power at the near reference point (NRP) in the seg, then subtract the distance power.

Answer

Rotate the lens 90 degrees and re-measure.

Answer

Measure the power at the geometric center of the seg, then subtract the distance power.

Answer

Place the seg line on the lensometer target and read the power directly.

Question 6

What is the acceptable tolerance for horizontal prismatic imbalance at the patient's pupillary distance (PD) for a prescription with no prescribed prism and a sphere power between ±0.25D and ±6.00D?

Accepted Answer

0.33Δ

Answer

0.25Δ

Answer

0.50Δ

Answer

1.00Δ