NOCE Ophthalmic Products and Materials 4 — Questions and Answers
Question 1: Which coating type reduces internal lens reflections visible to others looking at the wearer's eyes?
- Hydrophobic coating
- Anti-reflective coating (Correct answer)
- Mirror coating
- Polarized treatment
Correct answer: Anti-reflective coating
Anti-reflective coatings reduce reflections on both lens surfaces, making lenses more cosmetically transparent so others can see the wearer's eyes clearly.
Question 2: A patient's polycarbonate lenses show crazing (fine surface cracks). The MOST likely cause is:
- Impact damage from an accident
- Contact with solvents or chemical cleaners (Correct answer)
- Prolonged UV exposure
- Incompatible AR coating application
Correct answer: Contact with solvents or chemical cleaners
Polycarbonate is sensitive to many solvents and harsh chemical cleaners, which cause stress crazing — a network of fine surface cracks.
Question 3: What is the main function of a hydrophobic coating on an ophthalmic lens?
- Blocks UV radiation
- Repels water and reduces smudging (Correct answer)
- Increases lens tint density
- Improves impact resistance
Correct answer: Repels water and reduces smudging
Hydrophobic (water-repelling) coatings cause water to bead and roll off the lens surface, reducing smearing from rain, sweat, and fingerprints.
Question 4: The base curve of an ophthalmic lens is BEST described as:
- The thinnest point of the lens
- The curvature of the front surface measured in diopters (Correct answer)
- The total optical power of the lens
- The distance between lens centers
Correct answer: The curvature of the front surface measured in diopters
The base curve refers to the front surface curve of the lens, expressed in diopters, which helps maintain proper optical performance and cosmetic appearance.
Question 5: Which sunglass lens tint color is generally BEST for enhancing contrast in low-light or overcast conditions?
- Gray
- Green
- Yellow/amber (Correct answer)
- Blue
Correct answer: Yellow/amber
Yellow and amber tints filter short-wavelength blue light and enhance contrast, making them ideal for low-light conditions like overcast days or dawn/dusk driving.
Question 6: When selecting a frame for a high minus prescription, which frame characteristic MOST reduces lens edge thickness?
- Large frame eye size
- Thick acetate construction
- Small, round frame eye size (Correct answer)
- Drill-mounted rimless design
Correct answer: Small, round frame eye size
Minus lenses are thickest at the edges; choosing a small, round frame minimizes the lens diameter and therefore reduces edge thickness significantly.
Question 7: A mirror coating on a sunglass lens works primarily by:
- Absorbing all visible light wavelengths equally
- Reflecting a portion of incoming light off the front lens surface (Correct answer)
- Polarizing horizontally reflected glare
- Increasing the tint density of the base lens
Correct answer: Reflecting a portion of incoming light off the front lens surface
Mirror coatings are metallic vacuum-deposited layers on the front surface that reflect a percentage of incoming light, reducing the total light transmission into the eye.
NOCE Ophthalmic Products and Materials 4
Which coating type reduces internal lens reflections visible to others looking at the wearer's eyes?