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