Frame Measurements

Question 1

What are Charniers?

Answer 1

The interjoining elements around the screw on the dowel point

Question 2

What are the types of bridge for a metal frame?

Answer 2

Nose pads
W-bridge
Strap
Comfort

Question 3

What are the types of bridge for a plastic frame?

Answer 3

Fixed pad
Keyhole
Regular
Asian fitting (nose pads)

Question 4

Where is the eye size measured? AKA?

Answer 4

Horizontally across the lens at the widest point lens edge to opposite lens edge
AKA “A” measurement

Question 5

Where is the distance between lenses (DBL) measured? AKA?

Answer 5

Horizontally across bridge at narrowest point (nasal edge of each lens)
AKA Bridge size

Question 6

Where is the maximum diameter measured? AKA?

Answer 6

Longest measurement across lens (usually diagonal)
Double distance from geometric centre to apex of furthest part of lens bevel
AKA Effective diameter (ED)

Question 7

How is the frame PD measured?

Answer 7

Outside edge of one lens to inside edge of the other lens (Eye size+DBL)

Question 8

What is the boxed lens size? AKA?

Answer 8

Size of the rectangle surrounding the lens (measured horizontally and vertically)
Horizontal AKA eye size, “A” measurement
Vertical AKA “B” measurement

Question 9

How do you measure the distance between centres?

Answer 9

Find the distance between the two geometrical centres of the lenses (middle of boxed lens)

Question 10

What is the distance between centres known as?

Answer 10

Frame PD

Question 11

Where do you measure the length to bend?

Answer 11

Dowel point to ear point

Question 12

Where do you measure the length of drop?

Answer 12

Ear point to end of side

Question 13

Where do you measure front to bend?

Answer 13

From lug point to ear point

Question 14

Where do you measure the total length of side?

Answer 14

Lug point to end of side (straighten first)
AKA front to bend + length of drop

Question 15

What is the “C” measurement?

Answer 15

Width of the lens along the HCL

Question 16

Where is the HCL located?

Answer 16

Line drawn through the geometric centres

Question 17

What is the distance between centres?

Answer 17

Distance between the geometric centres

Question 18

Where is the bridge width line?

Answer 18

5mm below HCL (parallel)

Question 19

How is the bridge width measured?

Answer 19

Narrowest point between pad surfaces, measured along bridge width line

Question 20

How is the crest height measured?

Answer 20

Vertical distance from HCL to midpoint of the lower edge of the bridge

Question 21

How is the bridge height measured?

Answer 21

Vertical distance from bridge width line to midpoint of the lower edge of the bridge (Crest height + 5mm)

Question 22

What is the bridge projection?

Answer 22

Distance from back plane of the frame to the centre of the back of the bridge

Question 23

How do you measure the distance between rims?

Answer 23

Distance between the nasal rims at a stated distance below the HCL

Question 24

What is the apical radius?

Answer 24

Radius of lower bridge edge

Question 25

What is the splay angle of pad?

Answer 25

The angle at which the nosepad sits, measured from 90 degrees to the front of the frame

Question 26

Where is the frame temple width measured?

Answer 26

25mm behind the back plane of the frame

Question 27

Where is the frame head width measured?

Answer 27

Distance between the ear points

Question 28

What is the line of the side?

Answer 28

Straight line through dowel and ear points

Question 29

What is the angle of let-back?

Answer 29

Horizontal angle between the inner surface of the side and the normal to the back plane of the frame front

Question 30

What is the angle of side?

Answer 30

Vertical angle between line of the side and the normal to the back plane of the frame

Question 31

What is the length to tangent?

Answer 31

Distance from dowel point to point where curl begins on a curl side