Applying Prentice's Rule 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 Applying Prentice's Rule flashcards as text
A compound lens is -3.00 -1.00 × 180. At a point 5 mm below the optical center, what power is used to calculate vertical prism?
Answer: -4.00 D
With the cylinder axis at 180°, the cylinder acts fully in the 90° (vertical) meridian, so vertical power = -3.00 + (-1.00) = -4.00 D.
Per ANSI Z80.1, what is the maximum allowable induced prism at the MRP for a single-vision lens with power greater than ±3.375 D?
Answer: 0.67Δ
ANSI Z80.1 allows a maximum of 0.67Δ at the MRP for lenses stronger than ±3.375 D due to greater sensitivity to OC displacement.
A frame's distance between boxing centers is 70 mm. Patient binocular PD is 62 mm. Lens power is -2.00 D; decentration is split equally. What prism is induced per eye?
Answer: 0.80Δ
Total decentration = 70 - 62 = 8 mm; per eye = 4 mm = 0.4 cm; Δ = 2.00 × 0.4 = 0.80Δ per eye.
Which of the following produces the MOST induced prism?
Answer: -3.00 D decentered 5 mm (1.50Δ)
Δ = 3.00 × 0.5 = 1.50Δ, which is greater than any other option listed.
A patient wears OD +4.00 D and OS plano. The OD is decentered 4 mm outward. How much horizontal prism imbalance exists between the two eyes?
Answer: 1.60Δ
OD: Δ = 4.00 × 0.4 = 1.60Δ; plano OS produces 0Δ regardless of decentration; total imbalance = 1.60Δ.
If both lens power and decentration are doubled, what happens to the induced prism per Prentice's Rule?
Answer: Prism quadruples
Δ = P × d; doubling both gives (2P)(2d) = 4Pd, so prism quadruples.
A patient's near PD is 58 mm but the frame OC distance is 64 mm. With a +2.50 D add, what total base-in prism is induced at near (both eyes combined)?
Answer: 1.50Δ BI total
Per eye decentration = 3 mm = 0.3 cm; Δ = 2.50 × 0.3 = 0.75Δ BI per eye; both eyes same direction so total = 1.50Δ BI.