ABO Optics & Lens Design 2

Question 1

Progressive addition lenses (PALs) differ from bifocals primarily because they:

Accepted Answer

Offer a gradual power change from distance to near

Answer

PALs provide a continuous, gradual power progression eliminating the visible segment line of bifocals.

Question 2

Add power in a bifocal lens is defined as:

Accepted Answer

Near power minus distance power

Answer

Add power equals the near prescription power minus the distance prescription power and is always a positive value.

Question 3

Lenticular lens design is most commonly used when:

Accepted Answer

Very high plus powers are needed

Answer

Lenticular design places full correction only in a central optical zone, reducing weight and thickness for very high plus prescriptions.

Question 4

Aspheric lens surfaces are used primarily to:

Accepted Answer

Reduce peripheral aberrations and allow a flatter lens profile

Answer

Aspheric surfaces vary in curvature across the lens to minimize spherical and peripheral aberrations while enabling a thinner, flatter design.

Question 5

In a toric lens, the two principal meridians are oriented:

Accepted Answer

Perpendicular to each other

Answer

A toric lens has two principal meridians at 90° to each other, each with a different curvature and power, correcting astigmatism.

ABO - American Board of Optometry Practice Test