ABO Ametropia/Ophthalmic Optics 3

Question 1

A spectacle lens with a base curve of +6.00 D and back surface power of -2.00 D has a front vertex power of approximately:

Accepted Answer

+4.00 D

Answer

In a thin lens approximation, total power = front surface + back surface = +6.00 + (-2.00) = +4.00 D.

Question 2

The far point of a 5.00 D myope is located:

Accepted Answer

20 cm in front of the eye

Answer

Far point distance = 1/F = 1/5.00 = 0.20 m = 20 cm in front of the eye for a myope.

Question 3

Chromatic aberration in the eye causes violet light to focus:

Accepted Answer

In front of red light

Answer

Short wavelength (violet) light is refracted more strongly than long wavelength (red) light, so it focuses anterior to red.

Question 4

A +3.00 D thin lens in air has a focal length of:

Accepted Answer

33.3 cm

Answer

Focal length f = 1/F = 1/3.00 = 0.333 m = 33.3 cm.

Question 5

Which condition is characterized by a refractive error caused by increased axial length without any change in corneal or lenticular power?

Accepted Answer

Axial myopia

Answer

Axial myopia results specifically from an elongated globe, placing the retina behind the focal point of the optical system.

ABO - American Board of Optometry Practice Test