FREE National Opticianry Competency Exam (NOCE) Optical Instrumentation Use Questions and Answers

Question 1

An optician uses a lens clock to measure the front surface of a lens and gets a consistent reading of +6.00 D in all meridians. When measuring the back surface, the reading is -8.00 D in the 180° meridian and -6.00 D in the 090° meridian. Assuming the lens clock is calibrated for an index of 1.53 and the lens material is crown glass (n=1.523), what is the nominal prescription of this lens in minus cylinder form?

Accepted Answer

+0.00 -2.00 x 090

Answer

To find the nominal prescription, combine the front and back surface powers. The front curve (F1) is spherical at +6.00 D. The back curve (F2) is toric. To write in minus cylinder form, the sphere power is the combination of the front curve and the most plus (least minus) back curve: +6.00 D + (-6.00 D) = +0.00 D. The cylinder power is the difference between the two back curves: (-8.00 D) - (-6.00 D) = -2.00 D. The axis of the minus cylinder is the meridian of the flattest (least minus) curve, which is 090°. Therefore, the prescription is +0.00 -2.00 x 090.

Question 2

When using a corneal reflex pupillometer to take a monocular pupillary distance (PD) measurement for progressive addition lenses, which of the following is a critical step for ensuring accuracy?

Accepted Answer

Ensuring the patient and dispenser are seated and at eye level with each other.

Answer

For accurate progressive lens fitting, both the patient and the dispenser should be seated comfortably and at the same eye level. This posture ensures the patient's head is in a natural position, preventing measurement errors that can occur if the patient is looking up or down at the dispenser.

Question 3

A client's new high-plus power eyeglasses are verified to be correct in the lensometer, but the client reports blurry vision. The original refraction was performed at a vertex distance of 12 mm, but the new frames sit 16 mm from the patient's cornea. Which instrument should be used to measure this discrepancy, and what is the likely effect on the perceived power?

Accepted Answer

Distometer; an increase in perceived plus power.

Answer

A distometer is the specialized tool used to measure vertex distance—the distance between the back surface of the lens and the front of the cornea. For plus-powered lenses, moving the lens further away from the eye increases its effective power. This increase in perceived power is likely the cause of the patient's blurry vision.

Question 4

An optician is preparing to adjust a pair of cellulose acetate frames for a patient. Which of the following instruments is most appropriate for making the frame material pliable, and what is a key precaution to take?

Accepted Answer

A hot air frame warmer; avoid concentrating heat in one spot to prevent damage.

Answer

A hot air frame warmer is the recommended and safest tool for adjusting most plastic frames, including cellulose acetate. It provides controlled, even heat. It is crucial to keep the frame moving and not concentrate the heat on a single area, as this can cause the material to burn, warp, or lose its finish.

Question 5

Before neutralizing an unknown lens in a manual lensometer, what is the first and most critical step the operator must perform?

Accepted Answer

Focus the eyepiece for their own eye.

Answer

The first step before using a manual lensometer is to calibrate it for the user's own refractive error by focusing the eyepiece. The user should turn the eyepiece counter-clockwise until the reticle (the black target inside) is blurred, and then turn it clockwise until the reticle is in sharp, clear focus. Failure to do this will result in inaccurate power readings.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

FREE National Opticianry Competency Exam (NOCE) Optical Instrumentation Use Questions and Answers