Ophthalmic Optics Flashcards
7 cards from real CPOA 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 flashcards as text
What is the purpose of a trifocal lens segment compared to a bifocal?
Answer: It adds an intermediate zone between the distance and near zones
A trifocal lens has three zones: distance, intermediate, and near, providing clear vision at all three working distances for presbyopic patients.
Which neutralization technique uses a lens clock (Geneva lens measure) to determine the approximate prescription of an unknown lens?
Answer: Lensometry with neutralization
A lens clock measures the curve on each surface of the lens, and combined with the lens index, the prescription can be approximated through surface power neutralization.
A patient's prescription is -3.00 -1.50 x 180. If this is transposed to plus cylinder form, the result is:
Answer: -4.50 +1.50 x 090
To transpose: algebraically add sphere and cylinder (-3.00 + (-1.50) = -4.50), change cylinder sign (+1.50), and rotate axis 90° (180° + 90° = 90°).
What is the purpose of UV-blocking treatment or material in ophthalmic lenses?
Answer: To protect the eye from ultraviolet radiation that can cause cataracts and macular damage
UV-blocking lenses absorb ultraviolet radiation (UVA and UVB) to help protect ocular tissues from cumulative UV damage linked to cataracts and macular degeneration.
In ophthalmic optics, what does the term 'meniscus lens' describe?
Answer: A lens with both surfaces curved in the same direction (concave-convex)
A meniscus lens has one convex and one concave surface curving in the same direction, which is the standard form used in modern ophthalmic lens design to reduce aberrations.
What does the term 'slab-off' refer to in ophthalmic lens fabrication?
Answer: Removing base-up prism from one lens to correct vertical imbalance in anisometropia
Slab-off is a process that removes base-up prism from one lens (usually the more minus lens) to compensate for vertical prismatic imbalance caused by anisometropia when the patient looks down to read.
What is the difference between specular and diffuse reflection in the context of ophthalmic optics?
Answer: Specular reflection is mirror-like from smooth surfaces; diffuse reflection scatters light from rough surfaces
Specular reflection follows the law of reflection from smooth surfaces (like polished lenses), while diffuse reflection scatters light in many directions from irregular or rough surfaces.