ABO Optics & Lens Design

Question 1

What is the vergence formula used to find image vergence after a lens?

Accepted Answer

L' = L + F

Answer

The vergence formula states that image vergence equals object vergence plus lens power.

Question 2

A lens with a power of +5.00 D has a focal length of:

Accepted Answer

20 cm

Answer

Focal length = 1/power, so 1/5 = 0.20 m = 20 cm.

Question 3

Which lens type is used to correct myopia?

Accepted Answer

Concave (minus)

Answer

Concave minus lenses diverge light to shift the focal point back onto the retina in myopic eyes.

Question 4

The approximate index of refraction of standard crown glass is:

Accepted Answer

1.52

Answer

Standard crown glass has a refractive index of approximately 1.523, making it the traditional ophthalmic lens baseline.

Question 5

A higher Abbe value (V-number) in a lens material indicates:

Accepted Answer

Less chromatic aberration

Answer

A higher Abbe value means less dispersion of light into its component colors, resulting in less chromatic aberration.

ABO - American Board of Optometry Practice Test