General Optical Reference Material
Index
Frame Measurement Information
Pg. 3-4
Lens Styles
Pg. 4-5
Lens Illustrations
Pg. 6
Lens Materials Table
Pg. 7
Lens Terminology
Pg. 8
Fitting Different Materials
Pg. 8-10
Frame Types
Pg. 11-12
Base Curve
Pg. 12-13
Lens Options and Extras
Pg. 13-16
Frame Measurement Information
DBL: DBL stands for "distance between lenses." This measurement is taken from as the closest point between
the right and left lenses and is measured in millimeters.
Bridge: Bridge is the distance of the bridge of the frame and can be found on the frame along with the Eye size. Note:
this distance is not always the same distance as the DBL. Therefore when ordering lenses from your lab, be
sure to measure the DBL and don't just use the manufacturers bridge length found on the frame.
A/ Eye: A/Eye size are synonymous terms for the same measurement, and this length is put on the frame by the
manufacturer. See diagram above to reference this measurement. Our lab measures this length from inside
of the bevel to the inside of the bevel.
B: The B measurement is the basically the top of the frame to the bottom of the frame. (Our lab measures this
distance from the inside of the bevel to the inside of the bevel.
ED: When measuring the ED use the box method. See illustration below. We measure the ED as 2 x Maximum
Radius. Note that different shapes will determine different ED measurements, however an ED
measurement must be at least the same size or larger as the A measurement.
ED=2 x Radius
ED=2 x Radius
Pupil Distance (P.D.): Pupil Distance is the distance between the patients pupils, and usually taken with a
pupilometer. Pupil distance gives the lens its horizontal location.
Segment Height (Seg Height): Measurement in millimeters that determins where the distance prescription
stops and the near power begins for bifocal, trifocal. Seg.Ht is measured different for
progressive lenses in that you take the distance from the pupil down to the bottom
of the lens.
Geometrical Center: Absolute center of the lens.
Optical Center: Not to be confused with the geometrical center; the optical center (aka O.C.) is the distance
prescription focal point for the patient. Placement of the O.C. is determined by where the
patient's pupil is located in terms of height of the frame giving the lens its vertical location.
Bifocal
Progressive
Lens Styles
Single Vision Lenses
Lenses used for distance or reading prescriptions only.
Geometric and Optical Centers
Flat Top 28 Bifocal (FT-28, ST-28)
Bifocals are distance lenses with a segment of reading power added at the bottom.
Flat Top 35 Bifocals (FT-35, ST-35)
This version of a bifocal has distance power in the top of the lens and a slightly larger reading segment area.
Round 22 Bifocal (RD-22)
Bifocal with a completely round add power segment. Just as flat top bifocals come in larger sizes, round
bifocals also come in larger sizes. For example RD-24, and RD-25
Double Seg Straight Top 28
This lens has two FT-28 segments within the lens allowing someone to read normally looking down through
a segment and also allowing someone to look up through a segment for reading. This lens is popular with
people who requirea reading power in the upper portion of the lens for professional purposes.
Executive Bifocal
Executive bifocals are great for people who like to have a lot of add power to read with. This lens has add
power throughall of the lower part of the lens. See illustration.
Blended Bifocal
This unique lens gives the patient's vision a feel of a bifocal but cosmetically looks like a single vision lens
because the bifocal is blended into the lens.
7x28 (Trifocal)
Trifocals have a distance power in the top of the lens with an intermediate power and a reading power in the
bottom of the lens. Trifocals come in larger segments as well, for example 7x35, and 8x35.
Progressive
A progressive lens allows the patient to see distance in the top, reading in the bottom and everything else in
between. View illustration.
Lens Illustrations
Single Vision
Lens Materials
Material
CR-39 Plastic
CR-39 Polarized
CR-39 Transitions
Mid-Index 1.54
Mid-Index 1.55
Mid-Index 1.56
Mid-Index 1.56 Polarized
Mid-Index 1.56 Photochromic
Mid-Index 1.57
Polycarbonate
High Index 1.60
High Index 1.66
High Index Photochromic
Ultra High Index 1.70
Ultra High Index 1.71
Ultra High Index 1.74
Crown Glass
Photochromic Glass
Gray 3 Glass
Tan 3 Glass
High Index Glass 1.60
High Index Glass Photochromic
High Index Glass 1.70
High Index Glass 1.80
High Index Glass 1.90
Index of
Refraction
1.498/1.50
1.5
1.5
1.54
1.55
1.56
1.56
1.56
1.57
1.59
1.6
1.66
1.67
1.7
1.71
1.74
1.52
1.52
1.52
1.52
1.6
1.6
1.7
1.8
1.9
UV
ABBE Value Absorption
58
58
58
47
45
36-39
39
39
36
31
37
32
32
28
28
26
58
58
58
58
42
42
32
25
30.4
Specific
Gravity
84-88%
100%
100%
98%
90%
100%
100%
100%
90%
99%
100%
100%
100%
1.32
1.32
1.32
1.21
1.21
1.24-1.42
1.42
1.42
1.17
1.2
1.34
1.35
1.35
16%
96%
75%
99%
45%
99%
45%
30%
25%
2.54
2.54
2.54
2.54
2.73
2.73
2.99
3.37
4.02
Terminology
Index of Refraction:
The higher the index of refraction the thinner the lenses.
ABBE Value:
The higher the value the less chromatic aberration. (ABBE value of the human eye is between 43-45)
UV Absorption:
Amount of Ultra Violet light that is absorbed by the material.
Specific Gravity:
The lower the gravity, the lighter the lenses.
Photochromic Lenses:
Are activated by UV light, causing them to darken and block UV light. Because of this the lenses
will begin to darken when any source of UV light is present.
Fitting Different Materials
When fitting a patient with glasses it's important to keep lens material in mind. Lens mateial can make
or break a patients glasses literally and figuratively. It's very important to keep your patient in mind
when choosing a material.Topics to help decide the correct material for your patient include:
Prescription
Safety
Lens Weight
Frame
Daily surroundings
Price
Optics
UV Protection
and more…
Choosing a lens material that is right for your patient can be confusing to your patient as they probably
don't know any differences, however this is very critical in your patients satisfaction, health and safety.
Below are some reasons for each of the above topics as to why these are so important to keep in mind while
choosing a material.
Prescription: Choosing a material for the prescription is important so that your patient's
desires are met. Cosmetically a patient's lenses can look very thick by simply choosing
the wrong material. As shown above, the higher the index of refraction the thinner the
lenses will become. Remember the old "coke bottle" glasses Mrs Johnson used to wear?
Let's not re-visit that embarrassment, especially since we have the technology these
days to get it right the first time. Plus you probably don't want them out and about
telling the whole world that they picked up a great pair of glasses at your establishment
when in reality those glasses aren't very flattering.
Safety: Safety can be a huge concern with regards to the material of your patient's lenses.
If you have a patient who needs "Safety" lenses, meaning they are approved by OSHA as being
considered "Safety Lenses;" than there is probably a reason for this. Perhaps they work
near machinery and need protection from flying debri, or your patient is a child and requires
Polycarbonate (Safest most impact resistant material made).
Lens Weight: Lens weight is always an issue if a patient has a higher prescription or a large
frame or even worse both. When a patient has a large frame then there is more material in the
frame making it heavier than a small frame with less lens material. Also if a patient has a
high prescription the lenses will be thicker therefore adding more lens material resulting
in heavy eyewear. Note: glass is the heaviest material available.
Frame: Choosing a frame for your patient is crucial. Cosmetics are always important to the
patient because obviously they would like to look good in their new glasses. Selecting a
frame that matches the patients prescription is important as well. If they have a high
prescription than a good idea may be selecting a frame that helps hide the lens thickness.
Lens material is important as well if the patient selects a rimless frame. If a rimless frame
is selected, than we always recommend a lens with a 1.59 index or higher.
Daily Surroundings: Something to keep in mind when considering lens material is daily
surroundings, routines etc. If your patient is in an industrial like atmosphere while wearing
their glasses than Poly may be the best route to take. If they are outside all the time, than
selecting a material that is available with Transitions or Polarized lenses would probably be best.
But if they are indoors and merely using their glasses for a little light reading or surfing the
internet, than regular CR-39 plastic is probably all they really need. Ultimately determining the
patients lifestyle is important.
Price: One of the largest determining factors of lens material may simply be cost. High index
materials are much more expensive than CR-39 plastic. Therefore a patient may be forced
to have their eyewear made with a less expensive material.
Optics: Clarity of the optics is obviously important so that your patient enjoys their eyewear.
Glass has the best clarity of all of the materials, but it is also the heaviest and least safe.
Therefore choosing a material for clarity can be a tough decision; plus getting a patient who
has always worn glass to try and switch materials can be very tough to try and talk into a
different material.
UV Protection: Because so much eye damage is caused by UV radiation, UV protection is crucial
to have. Therefore choosing a material with UV protection built into the lens can help protect
your patient from this damage. Poly and high index already have UV protection built into the
lens. However ordering a lens with Transitions or that is polarized will also automatically
provide your patient with this protection.
Bottom line when it comes to choosing a material for your patient health and safety are key.
After that they can go with any of the other bells and whistles to add onto their glasses that
will improve any off the above characteristics of their vision and economic budget.
Frame Types
There are three different main types of frames and they are: Metal, Zyl, Rimless and then under the Rimless
category there are two different types; Grooved Rimless and Drilled Rimless.
Metal - Metal frames are simply frames with a metal all the way around the lens.
Zyl - Zyl frames are frames that simply have plastic surrounding the lens.
Rimless - Rimless frames are those that appear to not have anything completely surrounding the lens.
Grooved Rimless: This type of frame will often times have the upper have of the frame
sounding the lens a normal Metal or Zyl frame, and the lower have will look as though there
isn't a frame around the lens. Grooved Rimless frames always have a groove that run the
circumfrence of the edge of the lens. This allows the lab to insert a piece of clear string
much like fishing line into that groove holding the lens into the frame.
Drilled Rimless: Drilled Rimless frames are frames that are attached to the lens by drilling
a hole or set of holes into the lens and attaching the frame with anchors, bushings, or nuts
and bolts, etc.
Metal Frame
Zyl Frame
Grooved Rimless
Drillmount Frame
Base Curve (lens and frame)
Lens base curve (BC) is the ammount of natural curve that the lens has.
Frame BC is the ammount of natural curve that the frame has.
Ideally you would like to have both BC's matching so that the lenses fit well inside the frame. However that
isn't always the case, and it's very easy for a lens to pop out of the frame due to the BC's not being close
enough for the lens to stay into the frame. Therefore it's important to understand the relationship between
BC's and how they change as prescriptions change. See chart on next page.
Base
Curve
9
8
7
6
5
4
3
2
1
x
x
x
x
x
x
pl
pl
x
x
x
x
x
x
-1
1
x
x
x
x
x
x
x
x
-2
-3
2
3
= both can share base curves
Prescription
x
x
x
x
x
x
x
x
x
-4
4
-5
5
x
x
x
x
x
x
-6
6
As you can see from the graph above, - prescriptions typically have a higher base curve with a lower powered
prescription. Well + powers are the opposite and have a higher base curve when the prescription is higher.
Now this chart isn't exact, however it depicts the typical trends of those two lenses.
The illustration below is a horizontal cross-section look and shows how the curve of the lens gets steeper as
the BC increases.
1 BC
3 BC
6 BC
9 BC
Lens Options and Extras
Once you and your patient have discussed frames and lenses, it's also a great idea to discuss lens extras
since this is a good area for you as the business to make extra money and your patient to absolutely love their
glasses. Here is a list of typical extras ordered from patients:
Photochromatic Lenses
Polarized Lenses
Anti-Reflective Coating (AR)
Tint
Solder
Mirror Coating
Scratch Coating
UV Coating
1.0 Center Thickness
Drillout a screw
Change Nose Pads
Change Temple Covers
Custom Shape
Engraving
Photochromatic Lenses - Lenses change from clear (or close to it) to a darker shade (almost sunglass
darkness) activated by UV radiation. A very popular brand of this type of lens is "Transitions."
These lenses also block 100% UV radiation.
Polarized Lenses - Lenses that reduce glare due to the components of the lens redirecting glare away from
your eyes. Polarized lenses are dark, come as sunwear only, and are very popular for the following activities;
watersports, skiing, hiking, biking, driving, fishing, and many more. Polarized lenses also block 100% UV
Radiation
Anti-Reflective Coating - AR Coating is great for reducing eye fatigue and strain, glare, and optically helps
a lens with a low ABBE value increases the quality of your vision. Most AR's come with some sort of scratch
warranty as well. In fact the newest AR coating Crizal Avance with Scotchgaurd Protection has a anti scratch coating included within the coating making it one of if not the most durable AR on the market.
Tint - A tint can be made pretty much however the patient desires. Tints can be solid or gradient meaning
that they can be one color all the way through the lens, or they can be one color but darket in one or more
area than other areas. For example, your standard pair of sunglasses are typically a Solid Grey 3; which means
that they are a solid density 3 all the way through the lens. If a lens is gradient than the lens is typically
darker at the top of the lens and lighter towards the bottom. Density values range from either 1-3 or A-C: and
they mean that the lower the number or letter, the lighter the tint, and the higher the number or letter the
darker the tint. As stated before your standard sunglass is usually a grey 3 or brown 3 (or grey C or brown C).
Mirror Coating - Mirror Coatings come as either a solid mirror or flash mirror. Solid mirror coatings are
just like a normal mirror, if your wearing them your friends wouldn't be able to see your eyes, they would
only be able to see themselves. A flash mirror however gives the lenses a flash look but the eyewearer's
eyes are still noticeable. Mirror coatings are available in different colors so please call your customer service
representatives to find out exactly which colors are available.
Scratch Coating - Scratch coatings are popular because they protect lenses from scratching to an extent. If
you were to run your glasses over with a car, or let your dog chew them up, well then a scratch coating
won't do much. However scratch coatings do protect lenses from normal wear and tear. TD2 is a very
popular scratch coating brand. Scratch coatings will often come with a warranty as well.
UV Coating - UV coatings are very important to the maintain the health of your eyes. Therefore we always
recommend UV protection to all eyewear sales. Many times nowadays UV protection is included in many
lenses already, however if it isn't than you may want to recommend a UV coating to your patient. Our
UV coating is applied just like a tint and takes just a few minutes to help protect your eyes for the lifetime of
the eyewear.
1.0 Center Thickness - This is an option that isn't for everyone simply because it's intended for those who
have a higher prescription. If we grind the lenses to a 1.0 CT than the outer portions of the lenses will be
thinner than if we run them normally. One problem that comes with grinding lenses with a 1.0 CT is that
they can become too thin and that's a bad thing because the lense may break or chip, or just not fit in
the frame.
Change Nose Pads - Whether a patient has lost their nose pads or would just like a new pair, this is an
easy procedure that gives the patient a feeling of a new or improved pair of eyewear.
Change Temple Covers - Temple covers are typically made of a less expensive plastic and eventually wear
down and break. Therefore patients will come into your office and request new temple covers and it's
important to know how to change them.
Custom Shape - Some patients will desire to have their lenses made into a custom shape. This is an option
that is possible depending upon the shape. This is important to clear with your lab before you say yes to
your patient. Some shapes are very easy to make while others aren't and a lab might vey well say no way
is this possible. Therefore be sure and check with your lab to see if this option is available.
Engraving - Engraving is an option that isn't requested very often but it can be a nice touch to a pair of
expensive eyewear if the patient is willing to pay for it. Traditionally this is an expensive option simply
because this procedure is done by hand. Some labs have a engraving maching that will do all the work for you.
Solder - In order to solder a frame you will not only need the equipment to do so, but frame soldering can
be a tricky and difficult process if you don't have any experience with it. Frame soldering is a nice option to
offer your patient if they can't afford a new frame. However it's important to keep in mind that even
though a frame is soldered, that frame is no where near as strong as it used to be. It isn't uncommon for a
frame to be soldered several times once it has been broken. Note: Titanium frames CAN'T be soldered.
Drillout a screw - Because accidents happen a broken screw inside the frame isn't an uncommon
possibility. However a very common possibility is that the frame can be ruinned while drilling the screw out.
This process requires the screw to basically be drilled out by hand allowing for accidents to happen. Many
times screws are made from a material that is more dense than the frame; therefore the drill bit will slip off
of the screw and drill a hole through the side of the barrel of the frame ruinning the frame. Many times
a lab won't drill out a screw unless they know that the patient is aware that this request is done at their
own risk. Meaning that if they do break the frame the lab won't have to pay for it.
If you have any qustions regarding any information within this packet of material, please contact your
Sunstar Opticl Company Sales Representative or Customer Service Department.
Information within this spreadsheet is intended for use of Sunstar Optical Company
customers only.