ABO NOCE Basic Opticianry Dispensing Instrumentation 2 — Questions and Answers
Question 1: A lensometer measures which of the following properties of an ophthalmic lens?
- Lens thickness and weight
- Vertex power, axis, and prism (Correct answer)
- Frame PD and segment height
- Base curve and lens diameter
Correct answer: Vertex power, axis, and prism
The lensometer (focimeter) measures vertex power, cylinder axis, and prismatic power of ophthalmic lenses.
Question 2: When using a manual lensometer to neutralize a single vision lens, which target appearance indicates the lens is properly focused?
- A blurred circle of light
- Clear, stationary lines with the mires centered (Correct answer)
- Rotating mire lines
- A split image that cannot be merged
Correct answer: Clear, stationary lines with the mires centered
Proper focus on a lensometer is indicated by clear, sharp mire lines that are stationary and centered on the reticle.
Question 3: The pupillary distance (PD) ruler is used primarily to measure which distance?
- The distance from the cornea to the back of the lens
- The horizontal distance between the patient's pupil centers (Correct answer)
- The vertex distance of the frame
- The segment height of a bifocal lens
Correct answer: The horizontal distance between the patient's pupil centers
A PD ruler measures the horizontal distance between the centers of the patient's pupils to ensure optical centers are properly aligned.
Question 4: Which instrument is specifically designed to measure the curvature of a contact lens or the base curve of a spectacle lens?
- Lensometer
- Radiuscope / lens clock (Correct answer)
- Pupillometer
- Distometer
Correct answer: Radiuscope / lens clock
A radiuscope (for contact lenses) or a lens clock (Geneva gauge) measures the curvature or sagittal depth of lens surfaces.
Question 5: The distometer is used in opticianry to measure which parameter?
- The optical center height of a bifocal
- The vertex distance between the back of the lens and the cornea (Correct answer)
- The interpupillary distance
- The lens diameter before edging
Correct answer: The vertex distance between the back of the lens and the cornea
A distometer measures vertex distance, which is the distance from the back surface of the spectacle lens to the apex of the cornea.
Question 6: A pupillometer differs from a PD ruler in that it:
- Measures corneal curvature instead of pupil distance
- Uses a light reflection from the cornea for more accurate monocular PD measurement (Correct answer)
- Can only measure distance PD, not near PD
- Is used exclusively for children
Correct answer: Uses a light reflection from the cornea for more accurate monocular PD measurement
A pupillometer uses corneal light reflexes to more accurately and objectively measure monocular pupillary distances compared to a manual PD ruler.
Question 7: When using a frame warmer (hot air blower) to adjust a plastic frame, the primary goal is to:
- Permanently reshape the frame without the risk of breakage
- Soften the acetate to allow adjustment without cracking (Correct answer)
- Sterilize the frame before dispensing
- Shrink the frame to a smaller size
Correct answer: Soften the acetate to allow adjustment without cracking
A frame warmer heats plastic acetate to make it pliable so the optician can adjust temple angles, pantoscopic tilt, and frame width without cracking the material.
ABO NOCE Basic Opticianry Dispensing Instrumentation 2
A lensometer measures which of the following properties of an ophthalmic lens?