Ophthalmic Products and Materials Questions and Answers 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 Questions and Answers flashcards as text
Which lens material has the highest Abbe value among commonly used ophthalmic lens materials?
Answer: Crown glass
Crown glass (ophthalmic crown) has the highest Abbe value of approximately 58, meaning it produces the least chromatic aberration.
What is the primary purpose of an anti-reflective (AR) coating on ophthalmic lenses?
Answer: Reduce glare and increase light transmission
AR coatings reduce surface reflections, increasing light transmission through the lens and reducing glare for the wearer.
A patient requires a photochromic lens. Which factor does NOT significantly affect the darkening speed of photochromic lenses?
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.
Which type of lens coating should be applied LAST during the coating process?
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.
What is the refractive index of standard CR-39 plastic lens material?
Answer: 1.50
CR-39 (allyl diglycol carbonate) has a refractive index of 1.50, making it the baseline for standard plastic ophthalmic lenses.
Which frame material is most commonly associated with allergic reactions in sensitive patients?
Answer: Nickel-containing metal alloys
Nickel-containing metal alloys are the most common cause of contact dermatitis and allergic reactions in eyeglass wearers.
What does the term 'specific gravity' refer to when describing lens materials?
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.