ABO NOCE Basic Opticianry Spectacle Dispensing Procedures 5 — Questions and Answers
Question 1: A patient receives a prescription of -0.50 – 2.00 x 090. When verifying with the lensometer, the cylinder axis should be confirmed at:
- 180 degrees
- 090 degrees (Correct answer)
- 045 degrees
- 135 degrees
Correct answer: 090 degrees
The cylinder axis in the prescription is 090°, and lensometer verification must confirm the cylinder power is oriented at exactly that axis.
Question 2: Prism thinning is a technique used primarily to:
- Increase the optical power of the lens
- Equalize the center thickness of lenses with different powers (Correct answer)
- Correct a vertical phoria
- Reduce chromatic aberration
Correct answer: Equalize the center thickness of lenses with different powers
Prism thinning (slab-off or base-up prism) compensates for the differential prismatic effect in anisometropic corrections, but in lens fabrication, 'prism thinning' typically refers to equalizing thickness.
Question 3: When dispensing a frame with a wrap angle greater than 5°, prescriptions above ±2.00 D may require:
- A larger frame size
- Compensated lens powers to account for oblique incidence (Correct answer)
- A stronger anti-reflective coating
- Polycarbonate material only
Correct answer: Compensated lens powers to account for oblique incidence
High wrap angles cause the lens to be tilted relative to the visual axis, requiring power compensation (tilt-induced sphere and cylinder) to maintain optical accuracy.
Question 4: The effective diameter (ED) of a lens is:
- The horizontal width of the lens blank
- The smallest circle that will completely enclose the lens shape (Correct answer)
- The diameter of the finished lens after edging
- The difference between B measurement and A measurement
Correct answer: The smallest circle that will completely enclose the lens shape
The effective diameter is the diameter of the smallest circle that entirely encloses the lens shape, used to determine minimum blank size needed.
Question 5: A frame's DBL (distance between lenses) is 20 mm and a patient's bridge width is 14 mm. This frame will likely:
- Fit perfectly
- Sit too high on the nose
- Slip down and sit too wide on the face (Correct answer)
- Cause excessive vertex distance
Correct answer: Slip down and sit too wide on the face
A DBL much wider than the patient's bridge width will cause the frame to rest too low and slide down, since the bridge won't be supported by the nose.
Question 6: Which of the following is the correct sequence for dispensing new eyeglasses to a patient?
- Adjust frame → verify Rx → place on patient → check fit
- Verify Rx → adjust frame to patient → instruct patient on care and use (Correct answer)
- Place on patient → verify Rx → adjust frame
- Instruct patient → verify Rx → adjust frame
Correct answer: Verify Rx → adjust frame to patient → instruct patient on care and use
Best dispensing practice requires verifying the prescription accuracy first, then fitting/adjusting the frame to the patient, and finally educating the patient on lens and frame care.
Question 7: A patient reports that their new glasses feel 'swimmy' (objects appear to move). This is most commonly caused by:
- Insufficient UV coating
- A significant change in prescription or incorrect pantoscopic tilt with progressive lenses (Correct answer)
- Incorrect tint density
- A scratched lens surface
Correct answer: A significant change in prescription or incorrect pantoscopic tilt with progressive lenses
Peripheral distortion described as 'swimmy' is often due to adaptation to a new prescription or an incorrect pantoscopic tilt in progressives, which misaligns the corridor.
ABO NOCE Basic Opticianry Spectacle Dispensing Procedures 5
A patient receives a prescription of -0.50 – 2.00 x 090.
When verifying with the lensometer, the cylinder axis should be confirmed at: