Ophthalmic Products and Materials Flashcards
7 cards from real ABO NOCE Basic Opticianry practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ophthalmic Products and Materials flashcards as text
A patient needs a very high minus prescription (-12.00D). Which lens design feature would most effectively reduce edge thickness?
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.
Which coating is applied LAST during standard ophthalmic lens manufacturing?
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.
What material property makes memory metal (shape memory alloy) frames advantageous for patients with active lifestyles?
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.
A scratch-resistant hard coat on a plastic lens works by:
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.
Segment height in a lined bifocal refers to the measurement from:
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.
Which factor most significantly affects the cosmetic appearance (thickness) of plus lenses?
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).
A patient's frame has a spring hinge. What is the primary functional purpose of a spring hinge?
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.