ABO NOCE Basic Opticianry Ophthalmic Products and Materials 3 — Questions and Answers
Question 1: Polycarbonate lenses are the preferred material for children's eyewear primarily because of their:
- Superior optical clarity and Abbe value
- High impact resistance meeting ANSI Z87.1 standards (Correct answer)
- Lighter weight than all other materials
- Ability to accept all lens coatings
Correct 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.
Question 2: What distinguishes Trivex from polycarbonate as a lens material?
- Trivex has a higher refractive index
- Trivex has a higher Abbe value and better optical clarity (Correct answer)
- Trivex is less impact resistant
- Trivex is heavier per unit volume
Correct 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.
Question 3: A patient's acetate frame becomes misaligned and tight. What is the correct method to adjust it?
- Bend it cold using frame pliers
- Heat it in salt/bead pan then adjust (Correct answer)
- Soak it in warm water then adjust
- Use a frame stretcher immediately
Correct 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.
Question 4: What is the base curve relationship described by Tscherning's ellipse used to determine?
- The optimal lens thickness for a given prescription
- The ideal front curve for each prescription to minimize oblique astigmatism (Correct answer)
- The minimum blank size needed for a frame
- The correct pantoscopic tilt for a frame
Correct 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.
Question 5: Photochromic lenses activate (darken) in response to:
- Visible light only
- Infrared radiation
- Ultraviolet radiation (Correct answer)
- Heat from sunlight
Correct answer: Ultraviolet radiation
Photochromic lenses darken when exposed to UV radiation, which triggers a chemical or structural change in the photochromic molecules.
Question 6: Which type of lens coating provides the most benefit for patients who frequently use digital devices in low-light environments?
- Standard UV coating
- Anti-reflective coating (Correct answer)
- Mirror coating
- Gradient tint
Correct answer: Anti-reflective coating
Anti-reflective coatings reduce glare and reflections from screens, improving contrast and reducing eye strain for digital device users.
Question 7: A lens with a 1.74 high-index material is compared to the same prescription in CR-39. The high-index lens will demonstrate:
- Lower chromatic aberration
- Higher chromatic aberration (Correct answer)
- Identical chromatic aberration
- No chromatic aberration with AR coating
Correct 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.
ABO NOCE Basic Opticianry Ophthalmic Products and Materials 3
Polycarbonate lenses are the preferred material for children's eyewear primarily because of their: