ABO Ophthalmic Dispensing 4

Question 1

When a patient complains of 'jack-in-the-box' phenomenon with new bifocals, the most likely cause is:

Accepted Answer

Segment set too high

Answer

The 'jack-in-the-box' effect occurs when the bifocal segment is fitted too high, causing objects to pop in and out of view abruptly at the segment line.

Question 2

The term 'effective diameter' (ED) of a lens refers to:

Accepted Answer

The diameter of the smallest circle enclosing the entire lens shape

Answer

ED is the diameter of the smallest circle that completely encloses the lens shape, used to determine minimum blank size needed.

Question 3

A patient's single vision lenses show prismatic displacement of images. Which instrument is used to measure this induced prism?

Accepted Answer

Lensometer (lensmeter)

Answer

The lensometer (focimeter) is used to measure lens power and to quantify prismatic effect by locating the optical center relative to the pupil position.

Question 4

For a frame with A=52, DBL=18, the standard PD (frame PD) equals:

Accepted Answer

70 mm

Answer

Frame PD = A + DBL = 52 + 18 = 70 mm; this represents the distance from one lens center to the other.

Question 5

A base curve of +6.00 D is selected for a +4.00 D lens. This is best described as a:

Accepted Answer

Corrected curve (best-form) lens

Answer

A corrected curve (best-form) lens uses a specific base curve chosen to minimize aberrations for a given prescription power.

ABO - American Board of Optometry Practice Test

ABO - American Board of Optometry Practice Test

ABO Ophthalmic Dispensing 4