NOCE Ophthalmic Optics and Lenses 3

Question 1

What type of aberration causes light rays at different distances from the optical axis to focus at different points?

Accepted Answer

Spherical aberration

Answer

Spherical aberration occurs because peripheral rays focus at a different point than paraxial rays due to the spherical lens surface.

Question 2

A high-minus lens is best fabricated with which base curve strategy to minimize edge thickness?

Accepted Answer

Flatter base curve

Answer

Flatter base curves on minus lenses reduce edge thickness by allowing the front surface to be less curved.

Question 3

The Abbe value (V-number) of a lens material describes its:

Accepted Answer

Resistance to chromatic dispersion

Answer

The Abbe value measures how much a material disperses light into its spectral components; higher values mean less chromatic aberration.

Question 4

A patient with -5.00 D prescription switches from glass (n=1.523) to polycarbonate (n=1.586). The new lenses will be:

Accepted Answer

Thinner at the edges

Answer

Higher index materials require less curvature to achieve the same power, resulting in thinner edges for minus lenses.

Question 5

Prentice's Rule states that prism power at any point equals:

Accepted Answer

Distance from optical center (cm) × lens power (D)

Answer

Prentice's Rule: Prism (Δ) = distance in cm × power in diopters (P = cF).

NOCE - National Opticianry Competency Examination Practice Test