Frame Measurements Flashcards
What are Charniers?
The interjoining elements around the screw on the dowel point
What are the types of bridge for a metal frame?
Nose pads
W-bridge
Strap
Comfort
What are the types of bridge for a plastic frame?
Fixed pad
Keyhole
Regular
Asian fitting (nose pads)
Where is the eye size measured? AKA?
Horizontally across the lens at the widest point lens edge to opposite lens edge
AKA “A” measurement
Where is the distance between lenses (DBL) measured? AKA?
Horizontally across bridge at narrowest point (nasal edge of each lens)
AKA Bridge size
Where is the maximum diameter measured? AKA?
Longest measurement across lens (usually diagonal)
Double distance from geometric centre to apex of furthest part of lens bevel
AKA Effective diameter (ED)
How is the frame PD measured?
Outside edge of one lens to inside edge of the other lens (Eye size+DBL)
What is the boxed lens size? AKA?
Size of the rectangle surrounding the lens (measured horizontally and vertically)
Horizontal AKA eye size, “A” measurement
Vertical AKA “B” measurement
How do you measure the distance between centres?
Find the distance between the two geometrical centres of the lenses (middle of boxed lens)
What is the distance between centres known as?
Frame PD
Where do you measure the length to bend?
Dowel point to ear point
Where do you measure the length of drop?
Ear point to end of side
Where do you measure front to bend?
From lug point to ear point
Where do you measure the total length of side?
Lug point to end of side (straighten first)
AKA front to bend + length of drop
What is the “C” measurement?
Width of the lens along the HCL
Where is the HCL located?
Line drawn through the geometric centres
What is the distance between centres?
Distance between the geometric centres
Where is the bridge width line?
5mm below HCL (parallel)
How is the bridge width measured?
Narrowest point between pad surfaces, measured along bridge width line
How is the crest height measured?
Vertical distance from HCL to midpoint of the lower edge of the bridge
How is the bridge height measured?
Vertical distance from bridge width line to midpoint of the lower edge of the bridge (Crest height + 5mm)
What is the bridge projection?
Distance from back plane of the frame to the centre of the back of the bridge
How do you measure the distance between rims?
Distance between the nasal rims at a stated distance below the HCL
What is the apical radius?
Radius of lower bridge edge
