Spectacle Dispensing Flashcards

What does the term 'optical center' of a lens refer to?

Answer: The point where light passes through without prismatic deviation

The optical center is the point on a lens through which light travels in a straight line without being bent by prism effect.

Pantoscopic tilt refers to:

Answer: The downward tilt of the lens bottom relative to the top

Pantoscopic tilt is the angle at which the bottom of the frame tilts toward the face, typically 8–12 degrees for optimum optics.

Which of the following best describes 'induced prism' in spectacle lenses?

Answer: Prismatic effect caused when the eye views through a point other than the optical center

Induced (unwanted) prism occurs when the pupil is decentered from the lens optical center, creating a prismatic shift per Prentice's Rule.

A lens with a base curve of 6.00 D and a front surface power of +6.00 D has a back surface power of -2.00 D. What is the approximate total lens power?

Answer: +4.00 D

Approximate total power equals front surface plus back surface: +6.00 + (-2.00) = +4.00 D.

Which adjustment corrects a frame that sits too low on the patient's face?

Answer: Close (narrow) the nose pads

Narrowing (closing) the nose pads raises the frame higher on the nose, lifting it to a better position.

Which type of lens tint absorbs more light in the blue end of the spectrum and is often marketed to improve contrast for outdoor activities?

Answer: Yellow/amber tint

Yellow and amber tints absorb short-wavelength blue light, which can enhance contrast in hazy or low-light outdoor conditions.

The term 'monocular PD' refers to:

Answer: The distance from each pupil to the center of the nose bridge individually

Monocular PD measures the distance from each pupil to the midpoint of the nose separately, allowing for asymmetrical placement of optical centers.