ABO NOCE Basic Opticianry Spectacle Dispensing Procedures 4 — Questions and Answers
Question 1: Vertex distance is the measurement from the:
- Front of the lens to the corneal apex
- Back surface of the lens to the corneal apex (Correct answer)
- Pupil center to the lens optical center
- Lens front surface to the spectacle plane
Correct answer: Back surface of the lens to the corneal apex
Vertex distance is measured from the back vertex of the lens to the front surface of the cornea (corneal apex), typically 12–14 mm.
Question 2: Which adjustment corrects a frame where one lens sits higher than the other when the patient wears it?
- Adjust the pantoscopic tilt symmetrically
- Adjust the nose pad heights unequally to level the frame (Correct answer)
- Reduce the temple spread
- Tighten all hinge screws
Correct answer: Adjust the nose pad heights unequally to level the frame
Uneven nose pad heights can compensate for facial asymmetry or unequal ear heights, leveling the frame in front of the patient's eyes.
Question 3: For a prescription with +5.00 D sphere, changing vertex distance from 12 mm to 14 mm will effectively:
- Have no clinical effect
- Reduce the effective plus power reaching the eye (Correct answer)
- Increase the effective plus power reaching the eye
- Change the cylinder axis only
Correct answer: Reduce the effective plus power reaching the eye
Moving a plus lens farther from the eye reduces its effective power at the corneal plane, so a longer vertex distance weakens the effective plus power.
Question 4: The minimum fitting height for a standard progressive lens is typically:
- 14 mm
- 18 mm (Correct answer)
- 22 mm
- 28 mm
Correct answer: 18 mm
Most standard progressive lenses require a minimum fitting height of approximately 18 mm to accommodate the full progression corridor.
Question 5: When a patient's bifocal segment top appears to float in and out of vision, the most likely cause is:
- Incorrect PD measurement
- Segment height set too low (Correct answer)
- Incorrect base curve on the lens
- Frame wrap angle too high
Correct answer: Segment height set too low
If the segment top is positioned too low, the patient must tilt their head or look down excessively, making the segment difficult to use consistently.
Question 6: During frame adjustment, acetate frames should be heated using:
- An open flame
- Hot sand or an air-bead frame warmer (Correct answer)
- Boiling water immersion
- A heat gun at maximum setting
Correct answer: Hot sand or an air-bead frame warmer
Hot sand or an air-bead frame warmer provides even, controlled heat appropriate for softening acetate without scorching or melting the material.
Question 7: The term 'face form' (wrap) describes:
- The curve of the frame front from temporal to temporal to follow face curvature (Correct answer)
- The angle the lens makes with the vertical plane
- The distance between lens centers
- The curvature of the lens base
Correct answer: The curve of the frame front from temporal to temporal to follow face curvature
Face form is the horizontal curvature of the frame front that matches the natural curvature of the face from one side to the other.
ABO NOCE Basic Opticianry Spectacle Dispensing Procedures 4
Vertex distance is the measurement from the: