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
A patient's prescription is OD: -2.25 +0.75 x 105. In minus cylinder form, the cylinder axis would be:
Answer: 015
In minus cylinder transposition, new axis = 105 + 90 = 195; since 195 > 180, subtract 180 to get 015.
Which of the following correctly describes the spherical equivalent?
Answer: Sphere plus half the cylinder
Spherical equivalent = sphere + (cylinder ÷ 2), used to approximate a spherocylindrical lens as a single sphere.
Transpose -4.00 +2.00 x 075. What is the complete transposed prescription?
Answer: -2.00 -2.00 x 165
New sphere = -4.00 + 2.00 = -2.00; new cyl = -2.00; new axis = 075 + 90 = 165.
What is the spherical equivalent of -3.00 +2.00 x 180?
Answer: -2.00
SE = -3.00 + (2.00 ÷ 2) = -3.00 + 1.00 = -2.00.
On a power cross, the value written at the axis position of a minus cylinder prescription represents:
Answer: The sphere power
At the axis meridian there is no cylinder contribution, so the power equals the sphere alone.
A prescription of +3.00 -1.00 x 090 is equivalent to which power cross?
Answer: +3.00 @ 090 and +2.00 @ 180
Axis 090 carries sphere only (+3.00); meridian 180 carries sphere + cylinder = +3.00 - 1.00 = +2.00.
When transposing, if the original axis is 090, the new axis after adding 90° is:
Answer: 180
090 + 90 = 180, which is the maximum valid axis value and is acceptable.