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
What is the purpose of an anti-static coating applied to ophthalmic lenses?
Answer: To prevent static electricity from attracting dust and particles to the lens surface
Anti-static coatings reduce the build-up of static electrical charge on lens surfaces, which would otherwise attract airborne dust, lint, and particles, making lenses harder to keep clean.
A patient reports that their AR-coated lenses have developed 'crazing' — a network of fine cracks in the coating. What is the most likely cause?
Answer: Exposure to heat, such as leaving glasses in a hot car
Heat causes the lens substrate and the AR coating to expand at different rates (different coefficients of thermal expansion), leading to stress and crazing or micro-cracking of the coating.
In a standard gradient tint used in fashion eyewear, how is the tint distributed across the lens?
Answer: Darkest at the top, gradually lightening toward the bottom
Standard gradient tints are darkest at the top and gradually lighten toward the bottom, shielding the eyes from overhead sunlight while allowing relatively clear vision through the lower reading portion.
What does the term 'blooming' refer to when describing anti-reflective coated lenses?
Answer: The characteristic residual color visible in the reflection from an AR-coated lens surface
'Blooming' refers to the characteristic residual reflection color (often green, blue, or purple) visible on AR-coated lenses, which results from the thin-film interference design of the multilayer coating stack.
Brown/amber tinted lenses are particularly preferred for which visual task or activity?
Answer: Driving and outdoor sports in variable lighting conditions requiring enhanced contrast
Brown/amber tints enhance contrast and depth perception by selectively filtering blue light and transmitting warmer wavelengths, making them excellent for driving and variable outdoor lighting conditions.
Which statement about the relationship between UV protection and lens tint darkness is accurate?
Answer: UV protection is independent of tint darkness and is determined by the lens material or UV coating chemistry
UV protection is determined by the UV-absorbing chemical properties of the lens material or applied UV coating, not by tint darkness; a clear lens with proper UV inhibitors can provide 100% UV protection.
Which manufacturing method is used to apply the multiple thin layers of an anti-reflective coating to ophthalmic lenses?
Answer: Physical vapor deposition (PVD) in a vacuum chamber
Physical vapor deposition (PVD) in a vacuum chamber is the standard method for AR coating; materials are vaporized and condense onto the lens as precisely controlled nanometer-thick films in layers.