Optical Parameters Anterior Chamber, Lens & Axial Length

Question 1

Assume the cornea has a power of 43D, the lens is 19D, the anterior chamber depth is 4.0mm, the aqueous is n=1.336. If the anterior chamber depth decreases by 1mm what happens to the equivalent power of the eye?

a. increases by 0.62D
b. decreases by 0.62D
c. increases by 2.8D
d. decreases by 2.8D
e. no change occurs

Answer 1

increases by 0.62D

Question 2

If the actual depth of the anterior chamber were 5mm, how many mm behind the front surface of the cornea (in the eye) would the entrance pupil appear to be located? Use total cornea power and the parameters of Gullstrand’s exact eye to calculate mathematically.

a. -3.5 mm
b. -4.0 mm
c. -4.5 mm
d. - 5.5 mm
e. –6.0 mm

Answer 2

c. -4.5 mm

Question 3

The normal gradient refractive index of the crystalline lens ___________

a. decreases the total effective power
b. increases the amount of spherical aberration.
c. shows that the index of refraction decreases from the surface to the center of the lens.
d. shows a higher index for younger lenses than for older lenses
e. indicates the rate of change of index is faster for younger patients than older patients

Answer 3

e. indicates the rate of change of index is faster for younger patients than older patients

Question 4

The entrance pupil of the human eye is a

a. real, erect, magnified image of the pupil.
b. virtual, inverted, minified image of the pupil.
c. virtual, erect, magnified image of the pupil.
d. virtual, inverted, magnified image of the pupil.
e. real, inverted, minified image of the pupil.

Answer 4

c. virtual, erect, magnified image of the pupil.

Question 5

If you moved a biomicroscope 4.5 mm to change focus from the front surface of the cornea to the anterior surface of the lens, then the depth of the anterior chamber should be approximately

a. 4.0 mm.
b. 4.5 mm.
c. 5.0 mm.
d. 5.5 mm.
e. 6.0 mm.

Answer 5

c. 5.0 mm.

Question 6

In comparison to the real pupil, the entrance pupil is about

a. 15% larger
b. 5% larger
c. the same size
d. 5% smaller
e. 15% smaller

Answer 6

15% larger

Question 7

Which of the following changes, alone, might in theory increase the total positive dioptric power of the eye?

a. increase the size of the retina
b. increase the size of the cornea
c. increase the refractive index of the cornea
d. increase the refractive index of the aqueous
e. increase the refractive index of the vitreous

Answer 7

d. increase the refractive index of the aqueous

Question 8

Which of the following is true in reference to the crystalline lens?

a. It is flatter on the posterior surface than on the anterior surface
b. It has a uniform index of refraction throughout
c. Its anterior radius of curvature is shorter than the posterior radius of curvature
d. It is approximately 6.0 mm in thickness when it is not accommodating
e. It has an average power of approximately 19-20D unaccoomodated

Answer 8

e. It has an average power of approximately 19-20D unaccoomodated

Question 9

Which of the following does not influence the size of the ocular entrance pupil

a. diameter of the real pupil
b. depth of the anterior chamber
c. the refractive index of the aqueous humor
d. the dioptric power of the cornea
e. All of the above influence the size of the ocular entrance pupil

Answer 9

e. All of the above influence the size of the ocular entrance pupil

Question 10

Of the frequency distribution curves for individual ocular components which one is leptokurtic and highly correlated with refractive error

a. power of the cornea
b. depth of the anterior chamber
c. power of the lens
d. axial length
e. size of the pupil

Answer 10

d. axial length