Log 4 - Reference Points & Multifocal Height

Question 1

When taking OC or seg height measurements on a metal frame, the dispenser must _____________________________ first.

Answer 1

Adjust the frame and nosepads

Question 2

For SV lenses with no prism, where is the MRP?

Answer 2

At the optical center

Question 3

If the OC’s aren’t lined up with a patient’s pupils, it will induce:

Answer 3

Prismatic effect

Question 4

f the wearer’s PD is equal to the frame PD, what is the face-form recommendation?

Answer 4

No face form

Question 5

What is the Prentice Rule?

Answer 5

used to calculate the effect of induced prism. Based on the power of the lens and the amount of displacement of the OC.
Prism = cF

Question 6

Every ___ degrees of pantoscopic tilt the OC height should be lowered ____

Answer 6

1. 2

2. 1 mm

Question 7

True or False

The MRP and the OC always coincide

Answer 7

False

Question 8

The ________ ______ is the line that contains the MRP

Answer 8

Datum Line

Question 9

Between lower limbus and lower lid measurement for bifocal seg heights, which is considered to be more consistent?

Answer 9

Lower Limbus

Question 10

______mm must be subtracted from the “Lower edge of pupil” finding when measuring Trifocal seg height.

Answer 10

1 mm

Question 11

Seg height should be moved _____ mm for each ___^ prescribed.

Answer 11

0.3 mm

1 prism diopter

Question 12

Multifocals for children should be placed _____ mm above the pupil center

Answer 12

4 mm

Question 13

The patient requires a 54/22 sized frame but you only have the frame in a 56/22 size. If the bifocal height in the larger frame is 17mm what would the height be in the smaller frame?

Answer 13

16mm (1/2 the difference between the oversized and smaller size)