ABO NOCE Basic Opticianry Ophthalmic Products and Materials 5 — Questions and Answers
Question 1: A patient needs a very high minus prescription (-12.00D). Which lens design feature would most effectively reduce edge thickness?
- Full-field aspheric design with higher index material (Correct answer)
- Flat-top bifocal segment
- Larger frame with more wrap
- Lower refractive index material
Correct answer: Full-field aspheric design with higher index material
Combining a high refractive index material with an aspheric design minimizes edge thickness in high minus prescriptions by reducing both center and edge bulk.
Question 2: Which coating is applied LAST during standard ophthalmic lens manufacturing?
- Hard coat
- UV coating
- Anti-reflective coating (Correct answer)
- Mirror coating
Correct answer: Anti-reflective coating
Anti-reflective coatings are vacuum-deposited as the final step after all other treatments, since they are fragile and must not be exposed to subsequent processing.
Question 3: What material property makes memory metal (shape memory alloy) frames advantageous for patients with active lifestyles?
- They are completely rigid and cannot bend
- They return to original shape after bending or distortion (Correct answer)
- They are lighter than all other frame materials
- They contain no metal allergens
Correct answer: They return to original shape after bending or distortion
Memory metal alloys (typically nickel-titanium) can undergo significant bending and return to their original shape, making frames resistant to permanent distortion.
Question 4: A scratch-resistant hard coat on a plastic lens works by:
- Making the lens surface as hard as glass
- Providing a harder intermediate layer that resists abrasion (Correct answer)
- Adding a self-healing polymer layer
- Converting the plastic surface to a glass-like compound
Correct answer: Providing a harder intermediate layer that resists abrasion
Hard coats provide a harder intermediate surface layer (typically silica-based) that resists abrasion better than bare plastic, though not as hard as mineral glass.
Question 5: Segment height in a lined bifocal refers to the measurement from:
- The center of the segment to the bottom of the lens
- The top of the segment to the top of the lens
- The bottom of the lens to the top of the bifocal segment (Correct answer)
- The optical center of the distance lens to the segment top
Correct answer: The bottom of the lens to the top of the bifocal segment
Segment height is measured from the lowest point of the finished lens to the top of the bifocal segment, establishing where the reading area begins.
Question 6: Which factor most significantly affects the cosmetic appearance (thickness) of plus lenses?
- Frame size and shape only
- The lens material's specific gravity
- Lens refractive index and frame size combined (Correct answer)
- The type of anti-reflective coating selected
Correct answer: Lens refractive index and frame size combined
Center thickness in plus lenses is primarily determined by both the refractive index of the material (higher index = thinner) and the frame size (larger frame = thicker lens).
Question 7: A patient's frame has a spring hinge. What is the primary functional purpose of a spring hinge?
- To allow the temples to fold flat for storage
- To allow the temples to flex outward past 90 degrees for better fit retention (Correct answer)
- To reduce the overall weight of the frame
- To prevent the frame from opening fully
Correct answer: To allow the temples to flex outward past 90 degrees for better fit retention
Spring hinges contain a coiled spring mechanism that allows temples to flex outward beyond 90 degrees, improving fit retention and reducing pressure on the sides of the head.
ABO NOCE Basic Opticianry Ophthalmic Products and Materials 5
A patient needs a very high minus prescription (-12.00D).
Which lens design feature would most effectively reduce edge thickness?