PS Images

Question 1

How many PS images are there?

a. 1
b. 2
c. 3
d. 4
e. 5

Answer 1

4

Question 2

The first Purkinje image produced in an unaccommodated eye viewing a distant object is_____

a. a real, inverted image located near the posterior surface of the lens.
b. a virtual, erect image located near the anterior surface of the lens.
c. a virtual, inverted image located in the vitreous chamber.
d. a virtual, erect image that is larger than all the other Purkinje images.
e. a real, erect image formed at the eye’s secondary focal point.

Answer 2

b. a virtual, erect image located near the anterior surface of the lens.

Question 3

Which of the Purkinje images changes the most when the eye accommodates from distance to near?

a. Purkinje image I
b. Purkinje image II
c. Purkinje image III
d. Purkinje image IV
e. None of the PS images changes during accommodation

Answer 3

c. Purkinje image III

Question 4

Purkinje image III is formed by reflection at the __________

a. anterior lens surface and is virtual and erect.
b. posterior lens surface and is real and inverted.
c. anterior lens surface and is real and inverted.
d. anterior lens surface and located near the eye’s principal plane.
e. anterior lens surface and in the unaccommodated eye is the smallest Purkinje image.

Answer 4

a. anterior lens surface and is virtual and erect.

Question 5

A small beam of light intersects the cornea in a perpendicular manner. Approximately how much of the incident light will be reflected to form the corneal reflex?

a. 0.5 %
b. 1.0 %
c. 2.5%
d. 4.0%
e. 8.0%

Answer 5

c. 2.5%

Question 6

For an object at infinity, the 1st PS image is located

a. 3.8mm from the corneal apex (outside the eye).
b. 4.4mm from the corneal apex (outside the eye).
c. 2.9mm from the corneal apex (in the eye).
d. 3.8mm from the corneal apex (in the eye).
e. 4.3mm from the corneal apex (in the eye).

Answer 6

d. 3.8mm from the corneal apex (in the eye).

Question 7

The size of a light source is 10cm, and is positioned 12cm from the corneal apex. If the radius of curvature of the cornea is 8mm, where is the 1st PS image of the light source?

a. 2.5mm behind the cornea.
b. 3.2mm behind the cornea.
c. 3.9mm behind the cornea.
d. 4.5mm behind the cornea.
e. 5.2mm behind the cornea.

Answer 7

c. 3.9mm behind the cornea.

Question 8

8. Using the conditions in problem 7, what is the size of the 1st PS image of the mires?
   a. 2.5mm
   b. 3.2mm
   c. 3.9mm
   d. 4.5mm
   e. 5.2mm

Answer 8

b. 3.2mm

Question 9

Which PS image is the largest when the eye does not accommodate?

a. Purkinje image I
b. Purkinje image II
c. Purkinje image III
d. Purkinje image IV
e. None, all PS images are the same size

Answer 9

c. Purkinje image III

Question 10

Which PS image is the brightest?

a. Purkinje image I
b. Purkinje image II
c. Purkinje image III
d. Purkinje image IV
e. None. all PS images are equally bright

Answer 10

a. Purkinje image I

Question 11

Which PS image gives against motion when moving the light source?

a. Purkinje image I
b. Purkinje image II
c. Purkinje image III
d. Purkinje image IV
e. None, all PS images give with motion

Answer 11

d. Purkinje image IV

Question 12

Which is a real PS image?

a. Purkinje image I
b. Purkinje image II
c. Purkinje image III
d. Purkinje image IV
e. None, all PS images are virtual

Answer 12

d. Purkinje image IV

Question 13

13. Which PS image is inverted?
    a. Purkinje image I
    b. Purkinje image II
    c. Purkinje image III
    d. Purkinje image IV
    e. None, all PS images are erect

Answer 13

d. Purkinje image IV

Question 14

14. If, from the doctors perspective, the light source is moved to the left, the 1st
    PS image in the patient’s left eye should move_________
    a. nasally.
    b. temporally
    c. up
    d. down
    e. not at all.

Answer 14

a. nasally.

Question 15

15. An object for an optical system such as a camera can best form a clear and
    distinct real image when it_________
    a. is a good specular reflector of light.
    b. is a good diffuse reflector of light.
    c. does not reflect light.
    d. obeys Fresnel’s equation.
    e. is imaged through a negative lens.

Answer 15

b. is a good diffuse reflector of light.

Question 16

16. Which of the PS images is most difficult to observe?
    a. Purkinje image I
    b. Purkinje image II
    c. Purkinje image III
    d. Purkinje image IV
    e. None, all PS images are virtual

Answer 16

b. Purkinje image II

Question 17

17. Which of the PS images is a catoptric image?
    a. Purkinje image I
    b. Purkinje image II
    c. Purkinje image III
    d. Purkinje image IV
    e. None, all PS images are catadioptric images

Answer 17

a. Purkinje image I

Question 18

The 1st PS image in Gullstrand’s Exact (#1) Eye is located

a. at the corneal apex
b. in the anterior chamber
c. in the lens
d. in the vitreous but not close to the retina
e. in the vitreous and close to the retina.

Answer 18

c. in the lens

Question 19

If a luminous object is 5 meters in front of an eye, where is the 1st PS image located? Assume that the corneal radius of curvature is 10 mm and the corneal index of refraction is 1.4.

a. 1 mm or less behind the cornea (in the eye)
b. 3mm behind the cornea (in the eye)
c. 4mm behind the cornea (in the eye)
d. 5mm behind the cornea (in the eye)
e. 6mm or more behind the cornea (in the eye)

Answer 19

d. 5mm behind the cornea (in the eye)

Question 20

20. Suppose I placed a pen light well above my head while looking for the 4th PS image in a patient’s eye. I would expect to see the 4th PS image in______________
    a. the superior quadrant (above the center) of the pupil
    b. the inferior quadrant (below the center) of the pupil
    c. near the center of the pupil displaced slightly to the nasal side
    d. near the center of the pupil displaced slightly to the temporal side.

Answer 20

b. the inferior quadrant (below the center) of the pupil