Ophthalmic Optics and Principles 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 Optics and Principles flashcards as text
Which aberration causes off-axis image points to appear as lines or streaks rather than sharp points?
Answer: Astigmatism of oblique incidence
Astigmatism of oblique incidence occurs when light strikes a lens at an angle, producing two focal lines (sagittal and tangential) instead of a point focus.
What does the Abbe number (V-number) of a lens material indicate?
Answer: The degree of chromatic dispersion
The Abbe number measures how much a material disperses light into its component colors; a higher Abbe number means less chromatic aberration.
A patient's prescription reads -2.00 -1.00 × 090. What is the power in the 180° meridian?
Answer: -3.00 D
The 180° meridian is 90° away from the cylinder axis (090), so the full cylinder power is added: -2.00 + (-1.00) = -3.00 D.
What is the focal length of a +4.00 D lens?
Answer: 25 cm
Focal length (m) = 1/Power(D) = 1/4 = 0.25 m = 25 cm.
When transposing -3.00 +1.50 × 045, what is the correct transposition?
Answer: -1.50 -1.50 × 135
Transposition: new sphere = algebraic sum (-3.00+1.50=-1.50), new cylinder = sign-changed (-1.50), new axis = 90° rotated (045+90=135).
What is the primary purpose of antireflection (AR) coatings on ophthalmic lenses?
Answer: To reduce surface reflections and improve light transmission
AR coatings use thin-film interference to cancel reflected light, increasing light transmission and reducing glare for the wearer.
Which of the following best describes a Fresnel prism?
Answer: A thin flexible sheet with prismatic grooves
Fresnel prisms are thin, lightweight press-on sheets with concentric prismatic ridges that provide prismatic effect without significant weight or thickness.