NOCE Ophthalmic Optics and Lenses 5 — Questions and Answers
Question 1: A prism base direction of 'base-up' in the right eye will cause the image seen by that eye to be displaced:
- Downward (Correct answer)
- Upward
- Nasally
- Temporally
Correct answer: Downward
Prism displaces images toward the apex, so base-up prism causes the image to appear displaced downward (toward the apex, which is down).
Question 2: What is the minimum lens thickness required by ANSI Z80.1 for dress eyewear in most materials?
- 1.0 mm (Correct answer)
- 2.0 mm
- 1.5 mm
- 3.0 mm
Correct answer: 1.0 mm
ANSI Z80.1 requires a minimum center thickness of 1.0 mm for most dress eyewear lens materials (except glass, which is 2.0 mm).
Question 3: The distance vision zone of a progressive addition lens is located:
- Above the fitting cross (Correct answer)
- Below the fitting cross
- At the fitting cross level
- In the nasal portion of the lens
Correct answer: Above the fitting cross
In a PAL, the distance zone is positioned above the fitting cross, with the intermediate corridor below and near zone at the bottom.
Question 4: Which measurement determines where to place the optical center of a single-vision lens vertically?
- Monocular pupillary height (Correct answer)
- Fitting height
- Seg height
- Optical center height from the datum line
Correct answer: Monocular pupillary height
Monocular pupillary height (measured from the lowest point of the frame to the pupil center) determines vertical optical center placement for single-vision lenses.
Question 5: When a minus cylinder lens is held at a distance and rotated, the scissors effect seen with a retinoscope indicates:
- Oblique cylinder axis (Correct answer)
- Spherical power only
- No cylinder present
- Correct axis orientation
Correct answer: Oblique cylinder axis
The scissors motion (two reflexes moving in opposite directions) seen on retinoscopy indicates that cylinder is present with an oblique axis.
Question 6: Polycarbonate lenses require an anti-scratch coating because:
- The material is inherently soft and scratches easily (Correct answer)
- The material is too hard to bond with coatings
- It reacts with UV inhibitors
- Its high index makes it prone to crazing
Correct answer: The material is inherently soft and scratches easily
Polycarbonate is a relatively soft material compared to CR-39 or glass, making scratch-resistant coating essential for durability.
Question 7: The image formed by a converging lens when the object is placed between the focal point and the lens is:
- Virtual, erect, and magnified (Correct answer)
- Real, inverted, and magnified
- Virtual, inverted, and reduced
- Real, erect, and reduced
Correct answer: Virtual, erect, and magnified
When an object is inside the focal length of a converging lens, the image is virtual (same side as object), erect, and magnified — this is the principle of a magnifying glass.
NOCE Ophthalmic Optics and Lenses 5
A prism base direction of 'base-up' in the right eye will cause the image seen by that eye to be displaced: