The Box System

Question 1

what are other terms used to describe the longest horizontal length?

Answer 1

“eyesize” when referring to the frame and “lens size” when referring to a lens

Question 2

the A measurement is the

Answer 2

longest horizontal length

“eyesize” or “lens size”

Question 3

the longest vertical height of the frame is called the ___ measurement

Answer 3

B

Question 4

the C measurement is the:

Answer 4

horizontal midline

Question 5

the C line intersects:

Answer 5

the midpoint of the B measurement

Question 6

definition of the geometric center of the lens

Answer 6

is the point on the horizontal midline that is halfway between the two vertical lines bordering the lens

Question 7

what is the effective diameter (ED)?

Answer 7

the distance from the geometric center to the furthest point on the frame, multiplied by 2

Question 8

the effective diameter (ED) can be the same as the ___ measurement in some frames

Answer 8

A

Question 9

ED is usually a ____ measurement

Answer 9

diagonal

Question 10

bridge size is also called

Answer 10

DBL

Question 11

the DBL is defined as the

Answer 11

the distance between the inside nasal eye wire grooves across the bridge area at the narrowest point

Question 12

what is a concern of printed DBLs?

Answer 12

some frame manufacturers will state bridge sizes that do not match the DBL

Question 13

what is the frame PD?

Answer 13

the distance between geometric centers (frame center distance)

Question 14

what is another way to calculate the frame PD using other measurements?

Answer 14

A + DBL = Frame PD (FPD)

Question 15

what can the difference between the horizontal and vertical frame measurements tell you about the shape of the frame?

Answer 15

the larger the difference, the more rectangular the shape

Question 16

a high plus lens will be thicker where?

Answer 16

thicker on top and bottom

Question 17

a high minus lens will be thicker where?

Answer 17

thicker on the sides

Question 18

frame markings with __- ___- ___ indicate what measurements?

Answer 18

eyesize - bridge width - temple length

Question 19

how must you change the OC for degrees of panoscoptic tilt?

Answer 19

lower OC 1 mm for every 2 degrees of tilt

Question 20

BD prism causes eye to turn ___

Answer 20

up

Question 21

BU prism causes eye to turn ___

Answer 21

down

Question 22

prism in 1 eye requires unequal set heights, how many mm per prism diopter is needed?

Answer 22

0.29 mm per prism diopter

Question 23

the segment top is always displaced from its original location in the direction of the ___ of the vertical prism

Answer 23

apex

Question 24

minimum blank size (MBS) is based on:

Answer 24

• patient’s PD
• frame PD
• decentration
• ED

Question 25

minimum blank size (MBS) =

Answer 25

ED + total decentration + 2 mm

Question 26

total decentration =

Answer 26

(A + DBL) - PD

Question 27

alternative way total decentration can be calculated

Answer 27

the difference between the FPD and the patient’s PD