ABO NOCE Basic Opticianry Prescription Transposition 4 — Questions and Answers
Question 1: A patient's prescription is OD: -2.25 +0.75 x 105. In minus cylinder form, the cylinder axis would be:
- 015 (Correct answer)
- 195
- 105
- 090
Correct answer: 015
In minus cylinder transposition, new axis = 105 + 90 = 195; since 195 > 180, subtract 180 to get 015.
Question 2: Which of the following correctly describes the spherical equivalent?
- Sphere plus half the cylinder (Correct answer)
- Sphere minus the cylinder
- Sphere plus the full cylinder
- Half the sphere plus the cylinder
Correct answer: Sphere plus half the cylinder
Spherical equivalent = sphere + (cylinder ÷ 2), used to approximate a spherocylindrical lens as a single sphere.
Question 3: Transpose -4.00 +2.00 x 075. What is the complete transposed prescription?
- -2.00 -2.00 x 165 (Correct answer)
- -2.00 +2.00 x 165
- -4.00 -2.00 x 165
- -6.00 +2.00 x 165
Correct answer: -2.00 -2.00 x 165
New sphere = -4.00 + 2.00 = -2.00; new cyl = -2.00; new axis = 075 + 90 = 165.
Question 4: What is the spherical equivalent of -3.00 +2.00 x 180?
- -2.00 (Correct answer)
- -3.00
- -1.00
- -4.00
Correct answer: -2.00
SE = -3.00 + (2.00 ÷ 2) = -3.00 + 1.00 = -2.00.
Question 5: On a power cross, the value written at the axis position of a minus cylinder prescription represents:
- The sphere power (Correct answer)
- The cylinder power
- The spherical equivalent
- The add power
Correct answer: The sphere power
At the axis meridian there is no cylinder contribution, so the power equals the sphere alone.
Question 6: A prescription of +3.00 -1.00 x 090 is equivalent to which power cross?
- +3.00 @ 090 and +2.00 @ 180 (Correct answer)
- +3.00 @ 180 and +2.00 @ 090
- -1.00 @ 090 and +3.00 @ 180
- +3.00 @ 090 and -1.00 @ 180
Correct 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.
Question 7: When transposing, if the original axis is 090, the new axis after adding 90° is:
- 180 (Correct answer)
- 270
- 090
- 000
Correct answer: 180
090 + 90 = 180, which is the maximum valid axis value and is acceptable.
ABO NOCE Basic Opticianry Prescription Transposition 4
A patient's prescription is OD: -2.25 +0.75 x 105.
In minus cylinder form, the cylinder axis would be: