Prescription Transposition 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 Prescription Transposition flashcards as text
Which of the following prescriptions is the minus cylinder equivalent of +1.50 +1.00 x 180?
Answer: +2.50 -1.00 x 090
New sphere = +1.50 + 1.00 = +2.50; new cyl = -1.00; new axis = 180 - 90 = 090.
What is the purpose of transposing a prescription?
Answer: To convert between plus and minus cylinder notation
Transposition converts a prescription between plus and minus cylinder forms while keeping the optical effect identical.
If a prescription is -1.75 -0.50 x 020, what is the spherical equivalent?
Answer: -2.00
SE = -1.75 + (-0.50 ÷ 2) = -1.75 + (-0.25) = -2.00.
Transpose -0.25 -0.75 x 135 into plus cylinder form.
Answer: -1.00 +0.75 x 045
New sphere = -0.25 + (-0.75) = -1.00; new cyl = +0.75; new axis = 135 - 90 = 045.
In a spherocylindrical lens, the two principal meridians are always separated by:
Answer: 90°
The two principal meridians of any toric (spherocylindrical) lens are always 90° apart.
A prescription reads +0.50 -1.50 x 080. After transposition, the new cylinder power is:
Answer: +1.50
The transposed cylinder is always the opposite sign of the original cylinder, so -1.50 becomes +1.50.
Which scenario requires understanding prescription transposition in optical dispensing?
Answer: Verifying a lensometer reading in plus cylinder when the Rx is written in minus cylinder
Lensometers may display plus or minus cylinder; transposition lets the optician compare the reading to the written Rx regardless of form.