ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 3 — Questions and Answers
Question 1: The minimum fitting height for a lined bifocal segment is typically measured from:
- The geometric center of the lens
- The lower pupil margin to the bottom of the frame
- The lower lid margin to the bottom of the frame (Correct answer)
- The center of the pupil to the segment top
Correct answer: The lower lid margin to the bottom of the frame
Bifocal segment height is measured from the lower eyelid margin to the bottom of the lens (or frame groove), ensuring the segment line aligns properly.
Question 2: A patient's spectacles show excessive 'four-point touch' contact on the face. This indicates:
- The frame is too narrow
- The frame is properly fitted
- The frame is too wide and requires endpiece adjustment (Correct answer)
- The nose pads need to be widened
Correct answer: The frame is too wide and requires endpiece adjustment
Four-point touch at the temples and nose simultaneously with the frame bowing in the middle indicates the frame is too wide for the patient's face.
Question 3: Which lens material has the highest Abbe value, resulting in the least chromatic aberration?
- Polycarbonate (n=1.586)
- CR-39 plastic (n=1.498) (Correct answer)
- Trivex (n=1.53)
- 1.74 high-index glass
Correct answer: CR-39 plastic (n=1.498)
CR-39 has an Abbe value of approximately 58, the highest among common ophthalmic lens materials, giving the least chromatic aberration.
Question 4: When a patient reports that glasses feel tight on one side of the head only, the optician should first check:
- The prescription power
- Whether the temples are level
- The facial symmetry and temple alignment (Correct answer)
- The segment height
Correct answer: The facial symmetry and temple alignment
Unilateral tightness often results from unequal temple spread or the patient's facial asymmetry requiring one temple to be adjusted differently.
Question 5: In the boxing system, the 'datum line' is:
- The vertical line bisecting the lens
- The horizontal line through the geometric center of the lens (Correct answer)
- The line connecting the optical centers
- The line connecting the pupil centers
Correct answer: The horizontal line through the geometric center of the lens
The datum line is the horizontal line passing through the geometric center of the lens, used as the reference for vertical measurements in the boxing system.
Question 6: A patient with a +4.00 D prescription requires glasses. Which nose pad style generally provides the best support for heavy high-plus lenses?
- Keyhole bridge (no adjustable pads)
- Saddle bridge
- Adjustable silicone nose pads on a metal frame (Correct answer)
- Skull-temple plastic frame
Correct answer: Adjustable silicone nose pads on a metal frame
Adjustable silicone nose pads on a metal frame allow precise positioning to distribute the weight of heavy plus lenses evenly and prevent slipping.
Question 7: Decentration of a lens is used in opticianry to:
- Reduce lens thickness only
- Position the optical center at the patient's pupil or to create prescribed prism (Correct answer)
- Change the base curve of the lens
- Alter the segment height
Correct answer: Position the optical center at the patient's pupil or to create prescribed prism
Decentration moves the optical center relative to the geometric center of the lens to align with the patient's PD or to induce prismatic effect.
ABO NOCE Basic Opticianry Spectacle Dispensing and Fitting Questions and Answers 3
The minimum fitting height for a lined bifocal segment is typically measured from: