NOCE Ophthalmic Optics and Lenses 2

Question 1

A lens with a base curve of +6.00 D and a back surface power of -2.50 D has what front vertex power?

Accepted Answer

+3.50 D

Answer

Front vertex power equals base curve plus back surface power: +6.00 + (-2.50) = +3.50 D.

Question 2

Which lens form produces the least amount of oblique astigmatism for a given prescription?

Accepted Answer

Best form (corrected curve) lens

Answer

Best form lenses are designed with optimal base curves to minimize oblique astigmatism and peripheral distortions.

Question 3

A patient requires a prism of 4Δ base-in for the right eye. If split equally, how much prism is ground on each lens?

Accepted Answer

2Δ base-in on each lens

Answer

When prism is split equally, half the total prism (2Δ) is placed base-in on each lens.

Question 4

The critical angle in optics refers to the angle at which:

Accepted Answer

Total internal reflection occurs

Answer

The critical angle is the minimum angle of incidence at which total internal reflection occurs at the interface between a denser and less dense medium.

Question 5

What is the effect of increasing a lens's center thickness on its optical performance?

Accepted Answer

Increases back vertex power

Answer

Increasing center thickness increases the back vertex power of a plus lens due to the lens clock effect.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE Ophthalmic Optics and Lenses 2