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
Polycarbonate lenses are the preferred material for children's eyewear primarily because of their:
Answer: High impact resistance meeting ANSI Z87.1 standards
Polycarbonate's exceptional impact resistance, meeting ANSI Z87.1 industrial safety standards, makes it the standard of care for children's eyewear.
What distinguishes Trivex from polycarbonate as a lens material?
Answer: Trivex has a higher Abbe value and better optical clarity
Trivex has an Abbe value of about 45 compared to polycarbonate's 30, giving it significantly better optical clarity and less chromatic aberration.
A patient's acetate frame becomes misaligned and tight. What is the correct method to adjust it?
Answer: Heat it in salt/bead pan then adjust
Acetate frames must be warmed in a salt pan or frame heater (approximately 140-160°F) to become pliable before adjustment to prevent cracking.
What is the base curve relationship described by Tscherning's ellipse used to determine?
Answer: The ideal front curve for each prescription to minimize oblique astigmatism
Tscherning's ellipse identifies the theoretically ideal base curve for each prescription power to minimize oblique astigmatism when the eye rotates behind the lens.
Photochromic lenses activate (darken) in response to:
Answer: Ultraviolet radiation
Photochromic lenses darken when exposed to UV radiation, which triggers a chemical or structural change in the photochromic molecules.
Which type of lens coating provides the most benefit for patients who frequently use digital devices in low-light environments?
Answer: Anti-reflective coating
Anti-reflective coatings reduce glare and reflections from screens, improving contrast and reducing eye strain for digital device users.
A lens with a 1.74 high-index material is compared to the same prescription in CR-39. The high-index lens will demonstrate:
Answer: Higher chromatic aberration
Higher index materials have lower Abbe values, meaning they disperse light more and produce more chromatic aberration than lower-index materials like CR-39.