ABO NOCE Basic Opticianry Prescription Transposition 2 — Questions and Answers
Question 1: Transpose -3.00 +1.50 x 090 into minus cylinder form.
- -1.50 -1.50 x 180 (Correct answer)
- -1.50 +1.50 x 180
- -3.00 -1.50 x 090
- -4.50 +1.50 x 090
Correct answer: -1.50 -1.50 x 180
New sphere = -3.00 + 1.50 = -1.50; new cylinder = -1.50; new axis = 090 + 90 = 180.
Question 2: What is the spherical equivalent of +2.00 -1.00 x 045?
- +1.50 (Correct answer)
- +2.50
- +1.00
- +3.00
Correct answer: +1.50
Spherical equivalent = sphere + half the cylinder power = +2.00 + (-0.50) = +1.50.
Question 3: After transposing +1.00 -2.00 x 030, what is the new sphere?
- -1.00 (Correct answer)
- +3.00
- +1.00
- -2.00
Correct answer: -1.00
New sphere = original sphere + original cylinder = +1.00 + (-2.00) = -1.00.
Question 4: A prescription reads plano -2.50 x 160. What is its plus cylinder transposition?
- -2.50 +2.50 x 070 (Correct answer)
- +2.50 -2.50 x 070
- plano +2.50 x 070
- -2.50 +2.50 x 160
Correct answer: -2.50 +2.50 x 070
New sphere = 0.00 + (-2.50) = -2.50; new cyl = +2.50; new axis = 160 - 90 = 070.
Question 5: Which step is performed LAST when transposing a prescription?
- Rotate the axis 90° (Correct answer)
- Change the cylinder sign
- Add sphere and cylinder
- Record the new sphere
Correct answer: Rotate the axis 90°
The final step of transposition is rotating the axis by 90° (add or subtract 90, keeping result between 1 and 180).
Question 6: Transpose -0.50 +2.00 x 110. What is the new axis?
- 020 (Correct answer)
- 200
- 110
- 090
Correct answer: 020
110 + 90 = 200, which exceeds 180, so subtract 180: 200 - 180 = 020.
Question 7: The power cross for -1.00 DS shows which values in both meridians?
- -1.00 in both meridians (Correct answer)
- 0.00 in both meridians
- +1.00 in one meridian only
- -1.00 in one and 0.00 in the other
Correct answer: -1.00 in both meridians
A spherical lens (DS) has the same power in every meridian, so both principal meridians on the power cross read -1.00.
ABO NOCE Basic Opticianry Prescription Transposition 2
Transpose -3.00 +1.50 x 090 into minus cylinder form.