Ophthalmic Lenses and Materials Questions and Answers 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 Ophthalmic Lenses and Materials Questions and Answers flashcards as text
What is the purpose of an 'aspheric' lens design in ophthalmic optics?
Answer: To reduce peripheral aberrations and allow a flatter, thinner lens
Aspheric surfaces vary in curvature from center to periphery, reducing oblique aberrations and enabling flatter, more cosmetically appealing lenses.
Which property of lens materials is measured by the Abbe number (V-value)?
Answer: Chromatic dispersion (color fringing)
The Abbe number quantifies chromatic aberration—how much a material splits white light into its component colors.
When edging a polycarbonate lens, which wheel type is recommended?
Answer: Diamond-coated wheel at reduced speed with coolant
Polycarbonate requires diamond-coated wheels run at slower speeds with coolant to prevent crazing and delamination.
What is 'prism thinning' in lens fabrication?
Answer: Splitting prescribed prism between two lenses to minimize thickness
Prism thinning (or prism splitting) distributes prescribed prism equally between both eyes to minimize the thickness of each lens.
A lens is described as 'lenticular.' What does this indicate?
Answer: Only a central portion (aperture) carries the prescription; the carrier is plano or reduced power
Lenticular lenses have a central optical zone with the full prescription and a surrounding carrier of different (often zero) power to reduce weight and thickness.
Which statement about photochromic lenses is correct?
Answer: They darken faster in cold temperatures but lighten more slowly
Photochromic lenses activate faster in cold temperatures but fade back to clear more slowly because the chemical reaction is temperature-dependent.
What is the relationship between lens power and focal length?
Answer: Power (D) = 1 / focal length (m)
Lens power in diopters equals the reciprocal of the focal length in meters: P = 1/f.