ABO NOCE Basic Opticianry Ophthalmic Products and Materials 4 — Questions and Answers
Question 1: What is the primary advantage of titanium frames over standard metal frames?
- Lower cost and easier adjustment
- High strength-to-weight ratio and corrosion resistance (Correct answer)
- Better flexibility for sports use
- Easier soldering for repairs
Correct answer: High strength-to-weight ratio and corrosion resistance
Titanium offers exceptional strength with very low weight, and it is highly resistant to corrosion and hypoallergenic, making it ideal for sensitive patients.
Question 2: Which of the following best describes an aspheric lens design?
- A lens with the same curvature across its entire surface
- A lens with varying curvature that flattens toward the periphery (Correct answer)
- A lens designed specifically for astigmatism correction
- A lens with two distinct optical zones
Correct answer: A lens with varying curvature that flattens toward the periphery
Aspheric lenses have a front surface that gradually flattens from center to edge, reducing lens thickness and improving peripheral optical quality.
Question 3: A patient asks about the difference between polarized and standard tinted lenses. The key benefit polarized lenses provide is:
- Darker overall tint for bright sunlight
- Elimination of glare from horizontally reflected light (Correct answer)
- Better UV protection than standard tints
- Wider range of available tint colors
Correct answer: Elimination of glare from horizontally reflected light
Polarized lenses contain a filter that blocks horizontally polarized light, which is the type of glare reflected from flat surfaces like water and roads.
Question 4: What does the term 'Abbe value' (V-number) measure in an ophthalmic lens material?
- The material's resistance to impact
- The material's resistance to chromatic dispersion (Correct answer)
- The material's ultraviolet absorption
- The material's scratch resistance
Correct answer: The material's resistance to chromatic dispersion
The Abbe value measures a material's resistance to chromatic dispersion; higher Abbe values indicate less color fringing and better optical clarity.
Question 5: When fitting a patient with rimless mountings, which lens material is most appropriate for long-term durability?
- CR-39, because it drills cleanly
- Polycarbonate or Trivex, due to impact resistance at drill points (Correct answer)
- Glass, because it holds screws better
- High-index 1.74, because it is thinner
Correct answer: Polycarbonate or Trivex, due to impact resistance at drill points
Polycarbonate and Trivex resist cracking at drill holes better than other materials, making them the preferred choice for rimless and semi-rimless mountings.
Question 6: A patient's polycarbonate lenses appear to have a faint blue-white sheen when viewed against a dark background. This is most likely due to:
- A defective anti-reflective coating
- The natural birefringence and stress patterns in polycarbonate (Correct answer)
- Excessive UV absorption by the material
- Surface contamination from cleaning products
Correct answer: The natural birefringence and stress patterns in polycarbonate
Polycarbonate is a birefringent material with internal stress patterns from the injection molding process, causing a visible bluish sheen when viewed under polarized light or against dark backgrounds.
Question 7: Which frame temple style provides the most secure fit for active patients and children?
- Skull temples
- Library (straight) temples
- Cable (riding bow) temples (Correct answer)
- Paddle temples
Correct answer: Cable (riding bow) temples
Cable temples curl completely around the ear, providing the most secure grip and are preferred for active patients, children, and infants.
ABO NOCE Basic Opticianry Ophthalmic Products and Materials 4
What is the primary advantage of titanium frames over standard metal frames?