ABO NOCE Basic Opticianry Prescription Transposition 4

Question 1

A patient's prescription is OD: -2.25 +0.75 x 105. In minus cylinder form, the cylinder axis would be:

Accepted Answer

015

Answer

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?

Accepted Answer

Sphere plus half the cylinder

Answer

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?

Accepted Answer

-2.00 -2.00 x 165

Answer

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?

Accepted Answer

-2.00

Answer

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:

Accepted Answer

The sphere power

Answer

At the axis meridian there is no cylinder contribution, so the power equals the sphere alone.

ABO NOCE Basic Opticianry Practice Test