CPO CPO Basic Science 2

Question 1

A patient with a prescription of +10.00 D sphere is refracted at a vertex distance of 12mm.
If their new glasses are fit with a vertex distance of 8mm, what is the compensated power required to provide the same effective power as the refraction?

Accepted Answer

+10.42 D

Answer

+9.62 D

Answer

+10.00 D

Answer

+10.87 D

Question 2

Which of the following refractive errors is defined by the eye having different focusing power in different meridians, requiring a toric lens for correction?

Accepted Answer

Astigmatism

Answer

Myopia

Answer

Hyperopia

Answer

Presbyopia

Question 3

A patient looking 8mm below the optical center of a progressive addition lens (PAL) with a distance power of -3.00 D and an add power of +2.50 D will experience unwanted vertical prism. What is the primary source of this prismatic effect in the intermediate portion of the lens?

Accepted Answer

The combination of changing plus power and Prentice's rule.

Answer

The spherical distance power alone.

Answer

The add power creating base up prism.

Answer

The inherent design of the progressive corridor causing base down prism.

Question 4

The AC/A ratio represents the relationship between accommodative convergence and accommodation. A clinically 'high' AC/A ratio (e.g., 6/1) implies which of the following scenarios?

Accepted Answer

A large amount of convergence is generated for a small amount of accommodation.

Answer

The patient converges very little for each diopter of accommodation exerted.

Answer

The patient has a reduced ability to accommodate for near targets.

Answer

The patient is likely to be exophoric at near.

Question 5

The Purkinje images are reflections from the various optical surfaces of the eye. Which image is formed by the posterior surface of the crystalline lens and is characteristically inverted?

Accepted Answer

P4 (Fourth Purkinje image)

Answer

P1 (First Purkinje image)

Answer

P2 (Second Purkinje image)

Answer

P3 (Third Purkinje image)

Question 6

For light to be considered at 'optical infinity' with negligible vergence (i.e., parallel rays), the light source must be at least how far away from the observer?

Accepted Answer

6 meters (20 feet)

Answer

1 meter

Answer

3 meters

Answer

10 meters