frame parts, markings, and materials Flashcards
(49 cards)
What is a saddle bridge?
The area of the frame front between the lenses that rest on the patient’s nose
What does the saddle bridge do?
Distributes weight evenly across nose.
(cannot adjust the saddle bridge)
What is a modified saddle bridge?
- plastic bridge
- fixed nose pads
- more room for adjustment
What is a keyhole bridge?
- Plastic bridge
- looks like a keyhole
- Weight is supported by side pads
What is a pad bridge?
- It’s the pad attached to the frame by a metal arm.
- Used with a metal frame
What is the metal saddle bridge?
- It’s similar to the saddle bridge, but it is made out of metal and rests directly on the nose.
What does DBL stand for?
Distance between lenses
- It is measeured on the frame in millimeters
What is an eyewire or rim?
It is the frame that goes around the lenses
What is the boxing system?
- It is an imaginary box containing the lens and is used to determine the length and depth of the lens
What is the horizontal measure of the lens commonly referred to?
- EYESIZE
- denoted as the “A” measurement or “A” size.
What is the Vertical measure of the lens commonly referred to?
- “B” measurements or “B” size
How do you measure the boxing system?
- Measure from the inside of the eyewire on one side to the inside of the eyewire on the other side at the greater distance.
- Add 1mm to the value to compensate for the groove.
- Measured and noted in millimeters.
How is the Effective diameter measured?
- Measured from the geometric center of the longest outermost edge multiplied by two
What is the datum line or 180-degree line?
- It is the horizontal midline
- halfway between the top and bottom of the lens.
What is the geometric center known as?
- The box center is where the A and B measurements intersect.
What is it called when you find the difference between the A and B measurements?
Frame Difference or Lens Difference
What does DBC stand for?
Difference between center
How do you measure DBC?
Measured from the far left side of one lens opening to the far left of the other opening
(add frame eye size to the DBL)
How is segment height noted?
- Reference the top of the seg line to the lowest point of the box or lens, regardless of where it is directly below the center.
- Reference the distance below or above the horizontal midline called the seg drop or seg raise, respectively.
What is the formula to calculate the minimum blank size?
MBS = ED + decentration
Solve this problem by using MBS
A= 54 mm
DBL= 18mm
Patient PD = 64mm
ED= 56mm
54mm(A) + 18mm (DBL) - 64mm = 8mm decentration OU
8mm(decentration) + 56mm(ED) = 64mm minimum black size (MBS)
ADD 2mm for edge defects = 66mm MBS
Where is the end pieces?
attached temples to the frame front
What do the hinges do?
holds temples to frame the front
Where is the butt portion?
Closest to the front
