Optics and Refraction Flashcards
6 cards from real AOA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Optics and Refraction flashcards as text
The minimum add power for a presbyopic patient is determined by:
Answer: The amplitude of accommodation minus the required near demand reserve
The add is calculated so that after the add, the patient still uses only about half their remaining accommodation for comfortable sustained near work (Donder's rule of reserve).
In subjective refraction, the Jackson cross-cylinder (JCC) is used primarily to:
Answer: Refine the cylinder axis and power
The JCC is a combination of equal plus and minus cylinders 90° apart; flipping it tests whether rotating the cylinder axis or changing its power improves clarity.
Prentice's rule states that prism at a point in a lens equals:
Answer: Decentration (cm) × Lens power (D)
Prentice's rule: P (prism diopters) = c (cm of decentration) × F (lens power in diopters), used to calculate induced prism from decentered lenses.
The far point of a +3.00 D corrected hyperope (corrected at far) is located:
Answer: 33 cm behind the eye (virtual far point)
In uncorrected hyperopia, the far point is virtual (behind the eye); for a 3D hyperope, the far point is 1/3 m = 33 cm posterior to the eye, requiring a converging beam.
When performing the duochrome (bichrome) test, if both red and green appear equally clear, the endpoint indicates:
Answer: The refractive correction is optimally balanced (best sphere endpoint)
Equal clarity of red and green targets means the circle of least confusion is on the retina, placing the patient at the optimal spherical endpoint for their chromatic aberration.
Anisometropia is defined as a difference in refractive error between the two eyes greater than:
Answer: 1.00 D
A clinically significant difference of ≥1.00 D in spherical equivalent between the two eyes is the commonly used threshold for anisometropia.