ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 5 — Questions and Answers
Question 1: When verifying a finished pair of spectacles with a lensometer, the optician should neutralize the cylinder power by:
- Rotating the eyepiece until the target clears
- Rotating the lens until the lines are equal in clarity, then reading the power when lines are focused (Correct answer)
- Using the prism compensator dial only
- Adjusting the vertex distance setting
Correct answer: Rotating the lens until the lines are equal in clarity, then reading the power when lines are focused
To find cylinder power, rotate the lens until one set of lines is sharp, read that meridian, then rotate 90° for the other meridian; the difference is the cylinder power.
Question 2: A patient with a high-plus prescription complains their glasses feel very heavy on the nose. Which recommendation would MOST effectively reduce this problem?
- Switch to a larger plastic frame
- Use a high-index lens material to reduce center thickness (Correct answer)
- Increase the vertex distance
- Add more pantoscopic tilt
Correct answer: Use a high-index lens material to reduce center thickness
High-index materials reduce center thickness of plus lenses significantly, directly reducing the lens weight and nose pressure.
Question 3: The American National Standards Institute (ANSI) Z80.1 standard specifies that the allowable tolerance for sphere power in a finished lens (powers above ±6.50 D) is:
- ±0.13 D
- ±0.25 D
- ±0.37 D
- 2% of the stated power (Correct answer)
Correct answer: 2% of the stated power
ANSI Z80.1 allows ±2% of the stated power for lenses with sphere powers greater than ±6.50 D, rather than the fixed tolerance used for lower powers.
Question 4: When fitting wrap-around frames with a prescription, the optician must compensate for frame wrap angle because it introduces:
- Unwanted prism at the optical center
- Induced cylinder and sphere power changes (Correct answer)
- Base-down prism in the vertical meridian
- Increased chromatic aberration only
Correct answer: Induced cylinder and sphere power changes
Lens tilt in wrap-around frames induces oblique astigmatism (cylinder) and changes effective sphere power, requiring compensated lens powers.
Question 5: A patient whose frame sits too low on the nose (segment too high for bifocal) should have the nose pads adjusted by:
- Moving the nose pads closer together (narrowing)
- Moving the nose pads farther apart (widening) to raise the frame (Correct answer)
- Moving the nose pads farther apart to lower the frame
- Tightening the hinge screws
Correct answer: Moving the nose pads farther apart (widening) to raise the frame
Widening (spreading) nose pads moves the pads lower on the nose, which raises the frame and thus raises the segment position.
Question 6: In spectacle dispensing, the term 'seg drop' refers to:
- The prismatic effect at the segment top
- The vertical distance the segment is dropped below the distance optical center (Correct answer)
- How far the bifocal segment is inset from the distance optical center
- The height of the segment from the bottom of the frame
Correct answer: The vertical distance the segment is dropped below the distance optical center
Seg drop is the vertical distance between the distance optical center and the top of the bifocal segment, measured downward.
Question 7: A patient with a -6.00 D prescription selects a frame with a 54 mm eye size. If the patient's PD is 60 mm and the frame PD is 68 mm, what is the induced prism at the optical center if the lenses are not decentered?
- 0.00 prism diopters — no prism at the optical center
- 2.4 prism diopters base-in per eye
- 4.8 prism diopters base-out total
- 2.4 prism diopters base-out per eye (Correct answer)
Correct answer: 2.4 prism diopters base-out per eye
Using Prentice's Rule: P = cF = 0.4 cm × 6.00 D = 2.4 prism diopters base-out per eye (4 mm decentration outward in a minus lens = base-out prism).
ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 5
When verifying a finished pair of spectacles with a lensometer, the optician should neutralize the cylinder power by: