Lens materials, coatings, and dispensing terminology tested on optician certification exams.
34 cards · basic cards · AI-written, checked twice. Edit anything.
- What is the refractive index of CR-39 plastic?
- 1.498
- Define a high-index lens.
- A lens material with a refractive index above 1.53, allowing thinner lenses at the same power.
- What is the primary advantage of polycarbonate lenses?
- High impact resistance and safety, ideal for sports and children's eyewear.
- What material is Trivex?
- A urethane-based plastic lens material with high impact resistance and excellent optics.
- What is the main disadvantage of glass lenses?
- Heavy weight and poor impact resistance, creating a safety hazard.
- What does an anti-reflective coating do?
- Reduces light reflection from lens surfaces, improving light transmission and reducing glare.
- What type of coating protects against ultraviolet light?
- UV-protective coating or UV blocker.
- What does a scratch-resistant coating prevent?
- Surface scratches and abrasion damage to the lens.
- What is a photochromic lens?
- A lens that darkens in sunlight and clears indoors due to light-activated chemical changes.
- Define a progressive lens.
- A multifocal lens with a gradual change in power from distance at the top to near at the bottom, with no visible lines.
- What is a bifocal lens?
- A lens with two distinct optical powers, upper for distance and lower for near vision, separated by a visible line.
- What is a trifocal lens?
- A lens with three zones of power: distance (top), intermediate (middle), and near (bottom), separated by visible lines.
- What is a single-vision lens?
- A lens with uniform power throughout, designed for one focal distance.
- What is an aspheric lens?
- A lens with a non-spherical surface shape, reducing spherical aberration and providing thinner profiles.
- What is prism in an optical lens?
- The lateral displacement of light rays produced by an unequal change in power across the lens surface.