Lens Power And Thickness Flashcards
0
Q
B measurement
A
Vertical distance between the two horizontal tangents at the lens bevel
1
Q
A measurement
A
Horizontal distance between the 2 vertical tangents at the lens bevel
- eye size of frame
- measure from visible lens to visible lens, add 1mm
2
Q
Frame difference
A
Difference between the A and ab measurements
3
Q
DBL
A
Distance between lenses
-measured visible lens to visible lens, subtract 1mm
4
Q
DBC
A
Distance between geometric centers of the lenses
5
Q
Frame PD=
A
= A + DBL
6
Q
ED, effective distance
A
Twice the distance from the geometric center to the peak of the lens that is furthest from the geometric center
7
Q
Minimum blank size =
A
= ED + 2(decentration)
8
Q
Decentration =
A
= (frame PD-patient PD)/2
