CPOT Optical Dispensing & Lens Technology Flashcards

Which lens material has the highest Abbe value, indicating the least chromatic aberration?

Answer: CR-39 plastic

CR-39 plastic has an Abbe value of approximately 58, the highest among common ophthalmic lens materials, resulting in the least color fringing.

A lens prescription written as -2.00 -1.50 × 090 indicates:

Answer: Myopia with astigmatism, axis at 90 degrees

A minus sphere power indicates myopia, the minus cylinder corrects astigmatism, and the axis of 090° specifies the orientation of the cylinder.

Pupillary distance (PD) is measured to ensure that the optical centers of the lenses align with the:

Answer: Center of each pupil

PD measurement centers the optical zones of the lenses over each pupil to minimize induced prism and provide optimal visual comfort.

Antireflective (AR) coating on ophthalmic lenses primarily works by:

Answer: Using thin-film interference to cancel reflected light

AR coatings use multiple thin layers that create destructive interference, canceling reflected light and increasing light transmission to the eye.

Which type of lens is recommended for patients who need correction for distance, intermediate, and near vision in a single lens without visible lines?

Answer: Progressive addition lens (PAL)

Progressive addition lenses provide a smooth, gradual power change from distance at the top to near at the bottom, with no visible segment lines.

The base curve of an ophthalmic lens is defined as:

Answer: The reference curve from which other lens curves are calculated

The base curve is the standard reference surface of a lens blank from which the other curves are derived to achieve the desired prescription power.