FREE Board Certified Ophthalmologist Optics and Refraction Principles Questions and Answers

Question 1

A patient has a spectacle prescription of -10.00 D sphere.
The measurement from the posterior surface of the spectacle lens to the corneal apex (vertex distance) is 12 mm.
To achieve the same effective optical correction with a contact lens, what power should be prescribed?

Accepted Answer

-8.93 D

Answer

-11.36 D

Answer

-10.00 D

Answer

-9.00 D

Question 2

A patient is looking through their +5.00 D spherical lens at a point 6 mm below the optical center. Using Prentice's rule, what is the magnitude and direction of the induced prism?

Accepted Answer

3.0 prism diopters, base up

Answer

1.5 prism diopters, base down

Answer

3.0 prism diopters, base down

Answer

1.5 prism diopters, base up

Question 3

An eye's refractive state is such that parallel rays of light form two focal lines. The vertical focal line is focused 1.00 D in front of the retina, while the horizontal focal line is focused directly on the retina. How is this refractive error best classified?

Accepted Answer

Simple myopic astigmatism

Answer

Compound myopic astigmatism

Answer

Mixed astigmatism

Answer

Simple hyperopic astigmatism

Question 4

During static retinoscopy from a working distance of 67 cm, the examiner sweeps the light streak horizontally across the patient's pupil and observes a red reflex that moves in the same direction as the streak ('with' motion). Which of the following does this finding indicate?

Accepted Answer

The patient's far point is located behind the examiner's pupil.

Answer

The patient's far point is located between the examiner and the patient.

Answer

The patient's far point is located at the examiner's pupil.

Answer

The patient is myopic by more than -1.50 D.

Question 5

A biconvex lens made of crown glass (n=1.52) has a power of +5.00 D in air (n=1.00). If this same lens is fully submerged in water (n=1.33), what is its new approximate power?

Accepted Answer

+1.83 D

Answer

It becomes a minus-powered lens.

Answer

+7.80 D

Answer

+5.00 D

Question 6

Which of the following describes positive spherical aberration in the human eye?

Accepted Answer

Peripheral light rays are focused anterior to central (paraxial) light rays.

Answer

Central light rays are focused posterior to peripheral light rays.

Answer

Vertical light rays are focused at a different point than horizontal light rays.

Answer

Off-axis light rays create a comet-shaped blur.

A patient has a spectacle prescription of -10.00 D sphere.The measurement from the posterior surface of the spectacle lens to the corneal apex (vertex distance) is 12 mm.To achieve the same effective optical correction with a contact lens, what power should be prescribed?

A patient has a spectacle prescription of -10.00 D sphere.
The measurement from the posterior surface of the spectacle lens to the corneal apex (vertex distance) is 12 mm.
To achieve the same effective optical correction with a contact lens, what power should be prescribed?