Ophthalmic Products and Materials Questions and Answers Flashcards
6 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 6 Ophthalmic Products and Materials Questions and Answers flashcards as text
Photochromic lenses darken when exposed to UV light because they contain:
Answer: Silver halide crystals (glass) or organic photochromic molecules (plastic) that undergo a reversible chemical reaction when exposed to UV
Glass photochromics use silver halide crystals; plastic photochromics (like Transitions) use organic naphthopyran molecules. Both undergo a reversible photochemical reaction that causes darkening when UV-exposed.
Polarized lenses reduce glare primarily by:
Answer: Absorbing horizontally polarized light reflected from flat surfaces such as water, roads, and snow
Reflected glare from flat horizontal surfaces is predominantly horizontally polarized. Polarized lenses have vertically oriented transmission axes that absorb this horizontal light.
Which characteristic of a sunglass lens is described by the term 'luminous transmittance'?
Answer: The percentage of visible light that passes through the lens
Luminous transmittance is the ratio of the luminous flux transmitted through a lens to the incident luminous flux — essentially what percentage of visible light passes through.
A patient asks about the difference between standard single vision and aspheric lens designs. The key advantage of aspheric lenses is:
Answer: Reduced lens thickness, weight, and peripheral aberrations compared to spherical designs
Aspheric lenses use a varying surface curvature (not a perfect sphere) to reduce lens thickness and weight while controlling peripheral optical aberrations, particularly for plus lenses.
Blue light blocking lenses have become popular. Which part of the visible spectrum do they primarily filter?
Answer: The high-energy visible (HEV) blue-violet light range, approximately 380–450 nm
Blue light blocking lenses filter high-energy visible (HEV) blue-violet light in the approximately 380–450 nm range, which is thought to contribute to digital eye strain and may affect circadian rhythms.
Which lens coating is typically applied FIRST to a plastic lens blank before other coatings are added?
Answer: Hard coat (scratch-resistant coating)
Hard coat is applied first to provide a smooth, scratch-resistant base layer that protects the soft plastic substrate and provides adhesion for subsequent coatings like AR.