Ophthalmic Optics 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 flashcards as text
A patient's prescription is OD -4.00 -1.50 x 090. What is the power in the 180 meridian?
Answer: -5.50 D
In a minus-cylinder prescription, the sphere power acts along the axis meridian (090), and the full cylinder power is added 90° away (180°): -4.00 + (-1.50) = -5.50 D.
Which surface of a meniscus lens is typically convex?
Answer: The front (object-side) surface
In a standard ophthalmic meniscus lens, the front (convex) surface curves toward the world and the back (concave) surface curves toward the eye.
What does 'base curve' refer to in ophthalmic lens terminology?
Answer: The reference surface curvature, usually the front convex surface
The base curve is the reference surface power of an ophthalmic lens, most commonly expressed as the front (convex) surface power in diopters.
A cylinder lens with axis at 45° corrects astigmatism in which meridian?
Answer: The 135° meridian
A cylinder lens with axis at 45° has no power along the 45° meridian (the axis) and full correcting power in the 135° meridian (perpendicular to the axis).
The spherical equivalent of -3.00 -2.00 x 090 is:
Answer: -4.00 D
Spherical equivalent = sphere + (cylinder/2) = -3.00 + (-2.00/2) = -3.00 + (-1.00) = -4.00 D.
Which type of lens has exactly the same power in all meridians?
Answer: Spherical lens
A spherical lens has a single uniform power in every meridian because it is formed by a section of a sphere.
The back vertex power of a lens is measured from:
Answer: The rear surface to the rear focal point
Back vertex power is the vergence of light leaving the back (ocular) surface when parallel light enters the front surface, measured from the back surface to the rear focal point.