ABO NOCE Basic Opticianry Ophthalmic Optics and Principles Questions and Answers 2

Question 1

What is the prismatic effect at a point 4 mm below the optical center of a -3.00 D lens?

Accepted Answer

1.2Δ base up

Answer

1.2Δ base down

Answer

0.75Δ base up

Answer

0.75Δ base down

Question 2

What is the power cross for the prescription +2.00 -1.50 × 090?

Accepted Answer

+0.50 D at 090 and +2.00 D at 180

Answer

+2.00 D at 090 and +0.50 D at 180

Answer

-1.50 D at 090 and +2.00 D at 180

Answer

+2.00 D at 090 and -1.50 D at 180

Question 3

Transposing the prescription +3.50 -2.00 × 045 to plus-cylinder form gives:

Accepted Answer

+1.50 +2.00 × 135

Answer

+1.50 +2.00 × 045

Answer

+3.50 +2.00 × 135

Answer

+5.50 -2.00 × 135

Question 4

When two thin lenses are placed in contact with each other, the combined power is:

Accepted Answer

The algebraic sum of their individual powers

Answer

The product of their individual powers

Answer

Always less than either individual power

Answer

Determined by the separation distance only

Question 5

What is a prism diopter (Δ) and how is it defined?

Accepted Answer

A unit of prism power equal to 1 cm of displacement at 1 meter; P = d × F

Answer

A unit equal to 0.57° of angular deviation

Answer

The displacement of light in millimeters per diopter of lens power

Answer

The angle of minimum deviation through a prism in degrees

Question 6

What is the difference between back vertex power and front vertex power of a thick lens?

Accepted Answer

Back vertex power is measured from the back surface; front vertex power from the front surface; they differ for thick lenses due to lens thickness

Answer

They are always equal regardless of lens thickness

Answer

Front vertex power is always greater than back vertex power

Answer

Back vertex power applies to plus lenses only; front to minus lenses