Lens Coatings and Treatments 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 Lens Coatings and Treatments flashcards as text
Which lens treatment is specifically designed to filter high-energy visible (HEV) blue light in the 380–500 nm range?
Answer: Blue light blocking coating
Blue light blocking coatings selectively filter or reflect high-energy visible light in the 380–500 nm range, which is associated with digital eye strain and discussed as a factor in potential retinal stress.
Why do most photochromic lenses fail to darken effectively inside an automobile?
Answer: Car windshields block the UV radiation needed to activate the photochromic reaction
Car windshields are manufactured with UV-filtering glass or laminate that blocks the UV radiation required to trigger the photochromic darkening reaction, leaving the lenses mostly clear inside a vehicle.
When cleaning AR-coated lenses, which material should be avoided to prevent coating damage?
Answer: Paper towels or rough fabrics
Paper towels and rough fabrics contain abrasive fibers that can scratch the delicate AR coating layers; microfiber cloths are recommended because they are soft and non-abrasive.
Which tint color provides the most neutral, uniform color perception across the visible spectrum?
Answer: Gray tint
Gray tints absorb light relatively evenly across all visible wavelengths, providing neutral color perception without altering how colors appear, making them ideal for general outdoor use.
What is the primary advantage of a mirror coating applied to sunglass lenses?
Answer: Reduces the amount of light reaching the eye by reflecting it away from the lens surface
Mirror coatings reflect a significant portion of incident light before it reaches the eye, reducing light transmission and making them useful in extremely bright environments like snow or water sports.
What is the correct order in which coatings are typically applied to a standard AR-coated ophthalmic lens?
Answer: UV coat → hard coat → AR coat → hydrophobic coat
The standard sequence is UV primer or UV-absorbing base, followed by hard coat for scratch resistance, then the AR multilayer stack, and finally a hydrophobic/oleophobic topcoat as the outermost layer.
Which lens material inherently provides 100% UV protection up to 400 nm without requiring an additional UV coating?
Answer: Polycarbonate
Polycarbonate (and Trivex) lens materials inherently block 100% of UV radiation up to 400 nm due to the chemical composition of the polymer itself, without needing a separate UV coating.