Optics & Lens Design Flashcards

Prentice's Rule is used to calculate:

Answer: Prismatic effect at a point displaced from the optical center

Prentice's Rule states that induced prism (Δ) equals lens power (D) multiplied by decentration in centimeters.

A base-out prism placed before the right eye causes the image to appear displaced:

Answer: Nasally (toward the apex)

Images are displaced toward the apex of a prism; base-out means the apex is nasal, so the image shifts nasally.

Chromatic aberration in spectacle lenses produces:

Answer: Color fringing around objects

Chromatic aberration disperses different wavelengths to different focal points, creating visible color fringing, especially in the periphery.

Which optical aberration causes straight lines to appear curved (barrel or pincushion shaped) in the lens periphery?

Answer: Distortion

Distortion aberration results from variation in transverse magnification across the lens, making straight lines appear curved.

The optical center of a spectacle lens is defined as the point:

Answer: Where no prismatic effect is induced

At the optical center, a ray passes through the lens without prismatic deviation, making centering critical for patient comfort.

In minus cylinder notation, the cylinder axis meridian has:

Answer: The least minus (most plus) power of the two principal meridians

In minus cylinder form, the axis meridian carries no cylinder correction; the full minus cylinder power is added at the meridian 90° away.