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
A patient asks why their new AR-coated lenses show a faint green or purple reflection. How should you respond?
Answer: This residual reflection is normal and indicates the AR coating is functioning correctly
A slight residual green or purple reflection is characteristic of a properly applied AR coating and results from the specific wavelengths of light that the multi-layer stack does not fully cancel.
What does the Bayer abrasion test measure in the context of lens coatings?
Answer: The relative scratch resistance of a coated lens compared to a standard reference
The Bayer abrasion test tumbles sand or abrasive particles against a lens and measures how much haze develops compared to a reference lens to quantify scratch resistance.
Which type of coating is most appropriate for a patient who spends significant time under fluorescent office lighting and reports eyestrain from screens?
Answer: Blue light filtering (HEV) coating
Blue light (HEV) filtering coatings or treatments selectively reduce high-energy visible light from screens and fluorescent lighting, potentially reducing digital eyestrain.
A patient's AR-coated polycarbonate lenses develop a network of fine surface cracks (crazing). What is the most likely cause?
Answer: The lens was cleaned with a solvent incompatible with the coating, causing differential expansion
Solvents such as acetone or certain household cleaners dissolve or swell the coating or substrate differently, creating stress cracks known as crazing.
Which standard is commonly referenced in the US for classifying the level of UV protection provided by ophthalmic lenses?
Answer: ANSI Z80.3
ANSI Z80.3 is the US standard for non-prescription sunglasses and covers UV transmittance requirements, while ISO 8980-3 is the international equivalent for ophthalmic lenses.
A patient with a high minus prescription is concerned about the thick edge appearance of their lenses. Which coating decision would have NO direct effect on reducing edge thickness?
Answer: Applying an anti-reflective coating
AR coating improves the cosmetic appearance of lens edges optically by reducing reflections but does not change the physical thickness or geometry of the lens.
What is the main advantage of a multi-layer AR coating compared to a single-layer AR coating?
Answer: Multi-layer coatings reduce reflections across a broader range of wavelengths more effectively
Each layer in a multi-layer AR stack is optimized for different wavelengths, allowing destructive interference to cancel reflections across a wider visible spectrum than a single layer can achieve.