CPOA Ophthalmic Optics 4

Question 1

What does the addition (ADD) power in a bifocal or progressive prescription represent?

Accepted Answer

The extra plus power added to distance Rx for near vision

Answer

The ADD power is the additional plus power added to the distance prescription to bring near objects into focus for presbyopic patients.

Question 2

Which lens material has the highest Abbe value among commonly used ophthalmic lens materials?

Accepted Answer

CR-39 plastic

Answer

CR-39 plastic has an Abbe value of approximately 58, which is the highest among common ophthalmic materials, meaning it produces the least chromatic aberration.

Question 3

A patient complains of 'swim' or image movement when they move their head while wearing new progressive lenses. This is most likely caused by:

Accepted Answer

Peripheral distortion inherent to progressive lens design

Answer

Progressive addition lenses have areas of peripheral distortion and aberration that can cause a 'swimming' sensation, especially during adaptation.

Question 4

What is the optical significance of the geometric center versus the optical center of a lens?

Accepted Answer

The optical center is where prism power is zero; the geometric center is the physical middle of the lens

Answer

The optical center is the point through which light passes without prismatic deviation, while the geometric center is simply the physical middle of the lens blank.

Question 5

When dispensing high minus lenses, which edge treatment is most important for cosmetic and comfort reasons?

Accepted Answer

Roll and polish or bevel the thick edge

Answer

High minus lenses are thickest at the edges, so rolling and polishing (or proper beveling) improves cosmetics and reduces the 'ring' appearance of thick edges.

(CPOA) Certified Paraoptometric Assistant Practice Test

(CPOA) Certified Paraoptometric Assistant Practice Test

CPOA Ophthalmic Optics 4