ABO NOCE Basic Opticianry Lens Coatings and Treatments 2 — Questions and Answers
Question 1: Which lens treatment is specifically designed to filter high-energy visible (HEV) blue light in the 380–500 nm range?
- Anti-reflective coating
- Photochromic treatment
- Blue light blocking coating (Correct answer)
- Polarized filter
Correct 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.
Question 2: Why do most photochromic lenses fail to darken effectively inside an automobile?
- The lenses are already at maximum tint density before entering the car
- Car windshields block the UV radiation needed to activate the photochromic reaction (Correct answer)
- The heat inside the car prevents the photochromic chemical reaction
- Photochromic lenses only activate in temperatures below 50°F
Correct 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.
Question 3: When cleaning AR-coated lenses, which material should be avoided to prevent coating damage?
- Microfiber cloths
- Lens cleaning spray solution
- Paper towels or rough fabrics (Correct answer)
- Warm water rinse
Correct 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.
Question 4: Which tint color provides the most neutral, uniform color perception across the visible spectrum?
- Yellow/amber tint
- Gradient tint
- Gray tint (Correct answer)
- Brown tint
Correct 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.
Question 5: What is the primary advantage of a mirror coating applied to sunglass lenses?
- Provides maximum UV radiation protection
- Reduces the amount of light reaching the eye by reflecting it away from the lens surface (Correct answer)
- Increases lens durability and impact resistance
- Eliminates all glare from reflected surfaces
Correct 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.
Question 6: What is the correct order in which coatings are typically applied to a standard AR-coated ophthalmic lens?
- Hard coat → AR coat → UV coat → hydrophobic coat
- UV coat → hard coat → AR coat → hydrophobic coat (Correct answer)
- AR coat → hard coat → UV coat → hydrophobic coat
- Hydrophobic coat → AR coat → hard coat → UV coat
Correct 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.
Question 7: Which lens material inherently provides 100% UV protection up to 400 nm without requiring an additional UV coating?
- CR-39 plastic
- Standard crown glass
- Polycarbonate (Correct answer)
- High-index 1.60
Correct 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.
ABO NOCE Basic Opticianry Lens Coatings and Treatments 2
Which lens treatment is specifically designed to filter high-energy visible (HEV) blue light in the 380–500 nm range?