ABO Certification Training · Measurements& Markings Summary of Frame Measurements (Box System) A Horizontal measurement of box enclosing lens area B Vertical measurement of box enclosing
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ABO Certification Training
Part 6
Ophthalmic Frames
Principal Parts
Measurements & Markings
Measurements& Markings Summary of Frame Measurements (Box System)
A Horizontal measurement of box enclosing lens area
B Vertical measurement of box enclosing lens area
C Width of the lens along the central datum line
Effective Diameter Twice the distance from the geometric center of the lens to the bevel
farthest away from it
Frame Difference The difference between the horizontal and vertical measurements
Bridge Size (DBL) The least distance between the two lenses
GCD The geometric center distance is also known as the DBC, distance
between centers, and sometimes referred to as the FPD or Frame
PD, is the distance from the geometric center of one eyewire to the
geometric center of the other.
Overall Temple Length Distance from the center of the center barrel screw hole to the middle
of the bend
LTB Length to the bend. Measurement from the center of the barrel to the
middle of the bend
FTB Front to Bend. Distance between the plane of the frame front and the
bend of the temple. Applies to frames where the endpieces wrap
around and there is some distance between the frame front and the
beginning of the temple.
Horizontal
Lens
Decentration
The amount of
decentration
required in each
eye is equal to the
(GCD-PD) ÷2
Practice
• Determine the amount of horizontal decentration
required for the following
1) “A” measurement = 54
DBL = 16
PD = 62
3) “A” measurement = 50
DBL = 16
PD = 66
2) “A” measurement = 42
DBL = 14
PD = 50
4) “A” measurement = 58
DBL = 22
PD = 64
Minimum Blank Size
• The formula for determining the smallest
possible lens blank which will work for any
given frame and PD combination is as
follows:
Minimum Blank Size (MBS) = (GCD-PD) + ED
Practice
• Determine the “theoretical” minimum blank size for
each of the following:
5) “A” measurement = 58
DBL = 18
PD = 68
ED = 60
7) “A” measurement = 56
DBL = 16
PD = 64
ED = 59
6) “A” measurement = 52
DBL = 20
PD = 60
ED = 54
8) “A” measurement = 48
DBL = 14
PD = 50
ED = 50
Vertical Decentration
Vertical Decentration = seg height – (B measurement ÷2)
Practice
• Calculate vertical decentration of the bifocal segment
for each of the following:
9) “B” measurement = 52
Seg height = 23
11) “B” measurement = 50
Seg height = 28
10) “B” measurement = 48
Seg height = 24
12) “B” measurement = 46
Seg height = 19
Frame Materials Cellulose Acetated (zyl) Originally the most used material for plastic frames, it is a
cotton/wood flake product and can be produced in a great variety
of colors, textures and patterns. Dispensers often describe all
plastic frames as “zyl” but Zylonite is the correct trade name
specifically for cellulose acetate. Non-flammable
Cellulose Proprionate A durable material which is injection molded rather than being
cut from a flat sheet. Ideal for wrap around shapes. Requires
less heat for adjustments and lens insertions.
Optyl Epoxy material. Light in weight cannot be overheated or burned,
will not shrink. Optyl’s “memory” will cause it to revert to original
shape when heated.
Nylon Synthetic material made from coal, water and air. Light weight
and very strong. Often used in children’s frames and industrial
safety eyewear. Requires a good deal of heat for lens insertion
and adjustments.
Rubber Made of a combination of rubber and nylon sometimes used for
sunwear and sports eyewear. Frames have memory.
Carbon Fiber Strong, light weight, shape retention unaffected by hot weather.
Resistant to scratching and can be made nearly as thin as metal
frames.
Frame Materials Polycarbonate Highly impact resistant. Used for safety and sports.
Polymide/Copolymide Durable, light weight and flexible. Injection molded and holds
colors very well. Material will shrink when heated so lenses
should be cut to exact size.
Kevlar Also used for bullet-proof vests and sports equipment because
of its high tensile strength. Injection molded, very strong
material.
Memory Metal Made of special titanium and nickel alloy, frames have
memory so frame will return to original shape after accidental
twisting or bending.
Nickel Silver Holds shape the best of any metal combination. Not as
malleable as some other materials. Often used for standard
men’s navigator and pilot shape frames. Nickel Silver is the
most popular metal for eyeglass frames because it accepts
plating well and can be plated in a variety of colors.
Monel One of the most used metals for frames. Corrosion-resistant, it
works well with all colors. Monel eyewires are difficult to shape
for lenses, so the material is mostly used for temples, bridges
and fronts and less commonly for eyewires. Most important
features are strong solder joints and finish that does not wear
off.
Frame Materials Gold Used in combination with other materials such as nickel,
copper, beryllium and chrome. Frames are typically gold filled
or gold plated. Solid gold is rarely used due to the softness of
the material and high cost.
Silver Silver itself is not used in the manufacturing of frames due to
its softness. Instead, white gold is used.
Titanium Relatively new material. Very light weight, durable and
available in a variety of colors and styles.
Aluminum Light in weight, long lasting, may be anodized allowing for
many variations in color.
Stainless Steel Non-corrosive, strong and light in weight.
Frame Styles
Frame Selection By Shape of Face
Face Shape Description Recommended Frame Shape
Oval Normal Most shapes will be suitable
Oblong Long Deep frame preferably with low temple
attachment
Round Wide Relatively narrow frame preferably with a
high temple attachment
Square Wide Same criteria as round
Triangular Erect triangle Width of frame should approximately
equal lowest widest part of facial area.
Darker colors work well.
Diamond Inverted
triangle
Lighter looking frame is recommended
such as metal or rimless or lighter colors
in zyl.
Frame Selection
Prescription Considerations
Higher Minus Lenses Higher Plus Lenses
Recommend: Recommend:
Smaller eyesize Smaller Eyesize
Heavier Frame Material Sturdy Frame Construction
Rounder Shapes Rounder Shapes
Lightweight Lenses Small Frame Difference
Higher Index Material Adjustable Nose Pads
Antireflection coating Lightweight Lenses
Edge coating Higher Index Lens Material
Final Fitting
• Spectacle lenses are “well
fit” if they come into
physical contact with the
wearer at only three
points:
– Bridge of the nose (1)
– Side of the head behind
each ear (2)
Final Fitting
Final Fitting
A frame may be said to rotate around three axis known as the x, y and z axis as
illustrated on this slide. These can be useful to keep in mind in discussion of final fitting.
Final Fitting
Final Fitting
Frame Adjustments – An Overview
Problem Solution
Left lens in higher Bend left temple up or right temple down
Right lens in higher Bend right temple up or left temple down
Left lens is lower Bend left temple down or right temple up
Right lens is lower Bend right temple down or left temple up
Left lens in farther in Bend left endpiece in
Left lens is farther out Bend left endpiece out
Right lens is farther in Bend right endpiece in
Right lens is farther out Bend right endpiece out
Increase pantoscopic angle Bend both temples or endpieces down
Decrease pantoscopic angle Bend both temples or endpieces up
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