NOCE Spectacle Dispensing Procedures 3 — Questions and Answers
Question 1: A patient returns with a frame that is riding low, causing the bifocal to be too high. The nose pads are at their lowest adjustment. The best next step is:
- Remake the lenses with a lower segment
- Increase pantoscopic tilt to lower the frame front
- Order a frame with a deeper bridge (Correct answer)
- Reduce face form angle
Correct answer: Order a frame with a deeper bridge
If nose pad adjustment is exhausted, selecting a frame with a smaller or deeper bridge saddle will raise the frame's resting position on the nose.
Question 2: During a verification, the lensometer reading shows 2.00 prism diopters base-in in one lens not called for in the prescription. This is most likely caused by:
- Incorrect axis setting
- Optical center displaced nasally from the pupil center (Correct answer)
- Segment height error
- Incorrect vertex distance
Correct answer: Optical center displaced nasally from the pupil center
When the optical center is displaced nasally relative to the pupil, Prentice's Rule produces unwanted base-in prism in that lens.
Question 3: Which of the following is the correct procedure when setting the axis of an astigmatic correction on the lensometer?
- Rotate the eyepiece until the mire is sharpest regardless of line direction
- Align the axis wheel so the single line target is sharpest and note the axis reading (Correct answer)
- Use the prism compensator to neutralize the axis
- Set the drum to zero and rotate the lens
Correct answer: Align the axis wheel so the single line target is sharpest and note the axis reading
The axis is found by rotating the lens until the single-line mire is clearest, then reading the axis from the lensometer scale.
Question 4: A patient complains of neck strain when reading with new progressive lenses. Which fitting parameter is most likely responsible?
- Excessive face form angle
- Seg height set too high, forcing the patient to tilt the head back (Correct answer)
- Insufficient pantoscopic tilt
- Frame too wide for the patient's face
Correct answer: Seg height set too high, forcing the patient to tilt the head back
If the near zone is positioned too high, patients must adopt a chin-down or head-tilted-back posture to access it comfortably.
Question 5: The term 'effective diameter' of a spectacle lens refers to:
- The distance from the OC to the farthest lens edge, doubled (Correct answer)
- The actual diameter of the finished uncut lens blank
- The PD measurement used for decentration
- The diameter of the intermediate zone in a progressive
Correct answer: The distance from the OC to the farthest lens edge, doubled
Effective diameter (ED) is twice the distance from the optical center to the farthest edge of the frame's eye shape, determining the minimum blank size needed.
Question 6: When dispensing safety eyewear under ANSI Z87.1, which lens material meets the basic impact standard without additional testing for most occupational applications?
- Standard CR-39 at 2mm center thickness
- Polycarbonate at 2mm center thickness (Correct answer)
- High-index 1.74 at 1.5mm
- Trivex at 1.0mm center thickness
Correct answer: Polycarbonate at 2mm center thickness
Polycarbonate inherently meets the ANSI Z87.1 basic impact requirements at 2mm center thickness due to its high impact resistance.
Question 7: A patient's left lens shows 1Δ BU at the distance OC and the right lens shows 1Δ BD. What is the total vertical imbalance?
- 0Δ
- 1Δ
- 2Δ (Correct answer)
- 0.5Δ
Correct answer: 2Δ
When one eye has base-up and the other has base-down prism, the effects are additive, yielding a total vertical imbalance of 2Δ.
NOCE Spectacle Dispensing Procedures 3
A patient returns with a frame that is riding low, causing the bifocal to be too high.
The nose pads are at their lowest adjustment.
The best next step is: