Lens Treatments and Coatings Flashcards
7 cards from real NOCE 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 Treatments and Coatings flashcards as text
What is the primary purpose of an anti-reflective (AR) coating applied to ophthalmic lenses?
Answer: To reduce glare and surface reflections, improving visual clarity and cosmetic appearance
AR coatings reduce light reflections off lens surfaces, which minimizes glare, improves light transmission, and gives lenses a more cosmetically appealing clear appearance.
A patient asks why their CR-39 lenses need a UV-protective treatment. Which statement is most accurate?
Answer: CR-39 requires a UV-absorbing treatment to achieve UV400 protection because it transmits significant UV radiation on its own
Standard CR-39 does not inherently block UV radiation adequately, so a UV-absorbing additive or coating must be incorporated to achieve UV400 (blocks up to 400nm) protection.
Which mechanism causes photochromic lenses to darken when the wearer moves outdoors?
Answer: Exposure to ultraviolet (UV) radiation triggers a molecular change in the photochromic compounds
Photochromic lenses contain UV-sensitive molecules (such as naphthopyrans) that undergo a reversible structural change when exposed to UV radiation, causing the lenses to darken.
What is the main functional benefit of applying a scratch-resistant (hard) coating to ophthalmic lenses?
Answer: It reduces surface micro-abrasions that degrade optical clarity over time
Scratch-resistant coatings harden the lens surface to minimize micro-abrasions from everyday cleaning and handling, which preserves optical clarity over the life of the lens.
Which cleaning method is recommended for lenses with an anti-reflective coating?
Answer: Clean with a fresh microfiber cloth and an appropriate lens-cleaning solution or water
AR-coated lenses should be cleaned with a clean microfiber cloth and a lens-safe cleaning solution to avoid scratching the coating with abrasive materials or damaging it with harsh chemicals.
UV400 protection on ophthalmic lenses means the lens blocks all ultraviolet light up to which wavelength?
Answer: 400 nm
UV400 lenses block ultraviolet radiation up to 400nm, which covers both UVA (315–400nm) and UVB (280–315nm) wavelengths that can cause ocular damage.
Which combination of lens materials inherently blocks UV radiation up to 400nm without requiring an additional UV coating or treatment?
Answer: Polycarbonate and Trivex
Both polycarbonate and Trivex contain UV absorbers within their molecular structure, providing inherent UV400 protection without any additional coating.