NOCE Ophthalmic Products and Materials 5 — Questions and Answers
Question 1: Which frame material is the MOST flexible and corrosion-resistant, commonly used in rimless and semi-rimless mountings?
- Monel
- Titanium (Correct answer)
- Stainless steel
- Beryllium
Correct answer: Titanium
Titanium is extremely lightweight, highly corrosion-resistant, and strong enough for drill-mounted rimless frames that require durable thin mounting points.
Question 2: A patient asks about the difference between a gradient tint and a solid tint. The key difference is:
- Gradient tints block more UV radiation
- Gradient tints transition from darker at the top to lighter at the bottom (Correct answer)
- Solid tints are only available in gray
- Gradient tints are always polarized
Correct answer: Gradient tints transition from darker at the top to lighter at the bottom
A gradient tint fades from a darker concentration at the top of the lens (blocking overhead glare) to a lighter or clear area at the bottom (for reading or near tasks).
Question 3: When comparing CR-39 to high-index 1.74 material, which statement is MOST accurate?
- CR-39 produces thinner lenses for the same prescription
- High-index 1.74 has a higher Abbe value than CR-39
- High-index 1.74 produces thinner lenses but has more chromatic aberration (Correct answer)
- CR-39 has a higher refractive index than high-index 1.74
Correct answer: High-index 1.74 produces thinner lenses but has more chromatic aberration
High-index 1.74 produces thinner, lighter lenses for strong prescriptions but has a lower Abbe value (around 33) compared to CR-39 (Abbe ~58), meaning more chromatic aberration.
Question 4: Which ANSI standard specifies the minimum impact resistance requirements for dress eyewear sold in the United States?
- ANSI Z80.3
- ANSI Z87.1
- ANSI Z80.1 (Correct answer)
- ANSI Z136.1
Correct answer: ANSI Z80.1
ANSI Z80.1 covers requirements for prescription ophthalmic lenses including the drop-ball impact test that all dress eyewear lenses must pass before dispensing.
Question 5: A patient's AR-coated lenses show a persistent greenish or purplish residual reflection. This is MOST likely due to:
- A manufacturing defect in the lens substrate
- The normal residual reflection color of AR coating design (Correct answer)
- Contamination from cleaning solution
- Crazing of the lens surface
Correct answer: The normal residual reflection color of AR coating design
AR coatings are designed with a specific residual reflection color (often green or blue-violet) that results from the interference properties of the thin-film coating stack — this is normal and intentional.
Question 6: Which lens edge treatment is required when glazing drill-mounted (rimless) lenses to prevent cracking at the mounting holes?
- V-groove cutting
- Beveling and polishing the hole edges (Correct answer)
- Step beveling
- Flat-edge finishing
Correct answer: Beveling and polishing the hole edges
Drill-mounted lenses require the drilled holes to be chamfered (beveled) and polished to remove sharp stress risers that would cause the lens to crack under the mounting hardware.
Question 7: What is the primary purpose of a lens's oleophobic coating?
- Blocks UV light up to 400 nm
- Repels oils and fingerprints from the lens surface (Correct answer)
- Prevents photochromic molecules from degrading
- Increases the scratch resistance of the hard coat
Correct answer: Repels oils and fingerprints from the lens surface
Oleophobic coatings repel oils from skin and fingerprints, making lenses easier to clean and maintaining better optical clarity during wear.
NOCE Ophthalmic Products and Materials 5
Which frame material is the MOST flexible and corrosion-resistant, commonly used in rimless and semi-rimless mountings?