ABO NOCE Basic Opticianry Dispensing Instrumentation 3 — Questions and Answers
Question 1: On an automated lensometer, what advantage does it offer over a manual lensometer for verifying a progressive addition lens (PAL)?
- It can measure only the distance zone accurately
- It automatically maps the entire lens power distribution and identifies the corridor (Correct answer)
- It eliminates the need for ink dotting the lens
- It can only measure sphere, not cylinder
Correct answer: It automatically maps the entire lens power distribution and identifies the corridor
Automated lensometers can map the full power profile of a PAL, displaying the distance, intermediate, and near zones along with the corridor.
Question 2: The Geneva lens clock (lens gauge) is calibrated assuming a refractive index of:
- 1.498
- 1.523 (Correct answer)
- 1.600
- 1.740
Correct answer: 1.523
The Geneva lens clock is calibrated based on a refractive index of 1.523 (standard crown glass), so readings for high-index lenses must be corrected.
Question 3: Which tool is used to mark the optical center and axis of a spectacle lens before edging?
- The distometer
- The lensometer with a marking device (Correct answer)
- The pupillometer
- The frame warmer
Correct answer: The lensometer with a marking device
The lensometer is used to locate the optical center and axis of a lens, and a marking device (dotting system) places ink dots on the lens surface before it is edged.
Question 4: A frame ruler (millimeter ruler) used in dispensing most commonly measures which parameters?
- Vertex distance and pantoscopic tilt
- Eye size, bridge width, and temple length from frame markings (Correct answer)
- Segment height and optical center distance
- Base curve and lens diameter
Correct answer: Eye size, bridge width, and temple length from frame markings
A frame ruler is used to read or verify the three-part frame size (eye size × bridge + temple length) inscribed on the frame.
Question 5: A seg height gauge is used to measure:
- The power of a bifocal segment
- The vertical distance from the bottom of the frame to the top of the bifocal segment (Correct answer)
- The horizontal placement of a prism
- The distance PD compared to the near PD
Correct answer: The vertical distance from the bottom of the frame to the top of the bifocal segment
The seg height gauge measures the vertical placement of the bifocal segment top relative to the frame's lowest point, ensuring proper fitting for the patient's near vision needs.
Question 6: Which type of pliers is specifically designed to make precise bends in metal eyeglass frames without marring the surface?
- Tongue-and-groove pliers
- Pad-arm pliers with smooth, flat jaws
- Needle-nose pliers with serrated jaws
- Round-nose forming pliers with nylon tips (Correct answer)
Correct answer: Round-nose forming pliers with nylon tips
Nylon-tipped pliers protect the metal frame surface from scratches and dents while allowing controlled bending during adjustments.
Question 7: A prescription calls for 2.00 prism diopters base-in OD. When verifying this on the lensometer, the optical center dot should be displaced:
- Nasally (toward the nose) on the lens (Correct answer)
- Temporally (toward the ear) on the lens
- Superiorly on the lens
- Inferiorly on the lens
Correct answer: Nasally (toward the nose) on the lens
Base-in prism deviates light toward the base (inward), so the optical center must be displaced nasally (inward) to produce the prismatic effect.
ABO NOCE Basic Opticianry Dispensing Instrumentation 3
On an automated lensometer, what advantage does it offer over a manual lensometer for verifying a progressive addition lens (PAL)?