ABO NOCE Basic Opticianry Ophthalmic Products and Materials Questions and Answers 2 — Questions and Answers
Question 1: Which lens material has the highest Abbe value among commonly used ophthalmic lens materials?
- Crown glass (Correct answer)
- Polycarbonate
- Trivex
- High-index 1.74
Correct answer: Crown glass
Crown glass (ophthalmic crown) has the highest Abbe value of approximately 58, meaning it produces the least chromatic aberration.
Question 2: What is the primary purpose of an anti-reflective (AR) coating on ophthalmic lenses?
- Reduce glare and increase light transmission (Correct answer)
- Add UV protection
- Increase lens impact resistance
- Reduce lens weight
Correct answer: Reduce glare and increase light transmission
AR coatings reduce surface reflections, increasing light transmission through the lens and reducing glare for the wearer.
Question 3: A patient requires a photochromic lens. Which factor does NOT significantly affect the darkening speed of photochromic lenses?
- Patient's prescription power (Correct answer)
- Temperature
- UV intensity
- Lens material
Correct answer: Patient's prescription power
The prescription power of the lens does not significantly affect photochromic darkening speed; temperature, UV intensity, and lens material all do.
Question 4: Which type of lens coating should be applied LAST during the coating process?
- Hard coat
- Anti-reflective coat (Correct answer)
- UV coat
- Mirror coat
Correct answer: Anti-reflective coat
The anti-reflective coating is applied as the final top coat because it must be deposited over all other coatings to function correctly.
Question 5: What is the refractive index of standard CR-39 plastic lens material?
- 1.50 (Correct answer)
- 1.53
- 1.59
- 1.67
Correct answer: 1.50
CR-39 (allyl diglycol carbonate) has a refractive index of 1.50, making it the baseline for standard plastic ophthalmic lenses.
Question 6: Which frame material is most commonly associated with allergic reactions in sensitive patients?
- Nickel-containing metal alloys (Correct answer)
- Zyl/cellulose acetate
- Titanium
- Nylon
Correct answer: Nickel-containing metal alloys
Nickel-containing metal alloys are the most common cause of contact dermatitis and allergic reactions in eyeglass wearers.
Question 7: What does the term 'specific gravity' refer to when describing lens materials?
- The density of a material relative to water (Correct answer)
- The refractive index of the material
- The scratch resistance rating
- The impact resistance score
Correct answer: The density of a material relative to water
Specific gravity is the ratio of the material's density to that of water, and it determines the weight of the finished lens.
ABO NOCE Basic Opticianry Ophthalmic Products and Materials Questions and Answers 2
Which lens material has the highest Abbe value among commonly used ophthalmic lens materials?