Optical Instrumentation Use Flashcards
7 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Optical Instrumentation Use flashcards as text
On a lensometer, what does the drum reading indicate when the target lines are sharpest and the axis is at 45°?
Answer: The cylinder power at axis 45°
When lines are sharpest with the axis wheel at 45°, the cylinder axis of the lens is 45°, and the drum reading gives the cylinder power.
A Geneva lens clock placed on a flat (plano) surface should read:
Answer: 0.00 D
A properly calibrated Geneva lens clock reads 0.00 D on a flat surface, confirming the instrument is zeroed correctly.
When using a pupillometer for a patient with a significant facial asymmetry, which measurement mode provides the most accurate optical center placement?
Answer: Monocular PD measurement from the center of the nose
Monocular PD measurement references each eye independently from the nasal bridge, providing the most accurate placement for asymmetrical faces.
What is the function of the ink marker on a lensometer?
Answer: To mark the optical center and axis on the lens surface
The ink marker dots the lens surface through the lensometer stage, indicating the optical center and reference axis on the lens.
To verify the add power of a bifocal lens, a technician reads the distance power first, then repositions the lens to read the near segment. The add power equals:
Answer: Near power minus distance power
Add power = near (segment) power − distance power; this difference represents the additional plus power of the reading segment.
A keratometer (ophthalmometer) measures:
Answer: The curvature of the anterior cornea
A keratometer measures the radius of curvature (or power in diopters) of the anterior corneal surface, used in contact lens fitting.
When reading a lens on the lensometer and the dot (intersection point) falls to the right of center (toward 180°), which prism direction is indicated?
Answer: Base in (for right lens)
A dot displaced toward 180° (nasally for a right lens) indicates base-in prism, as the base is toward the direction of displacement.