UNIT 3: Tints, Coatings, and Special Lens Designs Flashcards
Electromagnetic Radiation
- Ultraviolet:
1) UVC: 200 - 275 nm Ozone Layer
2) UVB: 275 - 330 nm Sunburn
3) UVA: 330 - 400 nm Ocular Hazard - Visible Light:
1) 400 - 750 nm ROYGBIV - Infrared Heat
1) 750 - 1,000,000 nm
Light
- Light deviates from a source in waves
- Speed of light in air = 186,000 miles per
second. - Light striking a different medium is
reflected ( 4% from each lens surface ),
refracted or absorbed. - Speed of light in air divided by the speed of
light in medium = index of refraction.
The Metric System
1 meter = 39.37 inches
1 meter = 10 decimeters
1 meter = 100 centimeters
1 meter = 1000 millimeters
1 meter = 1 billion nanometer ( nm )
Lens Material Characteristics
- Index of refraction
- Abbe Value
- Specific Gravity
Index of refraction
When light strikes a new medium at an angle, the change in speed causes it to change direction. The higher the index, the greater the change.
Abbe Value
The higher the value , the less chromatic aberration present in a lens.
Specific Gravity
The ratio of the weight of a substance to the weight of water with the same volume. The lower the number, the lighter the lens.
Crown
Index: 1.52
Specific Gravity: 2.54
ABBE: 59
CR-39
Index: 1.498
Specific Gravity: 1.32
ABBE: 58
Spectralite
Index: 1.54
Specific Gravity: 1.21
ABBE: 47
Trivex
Index: 1.53
Specific Gravity: 1.11
ABBE: 45
Thin & Lite
Index: 1.60
Specific Gravity: 1.34
ABBE: 36
Polycarbonate
Index: 1.59
Specific Gravity: 1.20
ABBE: 31
Glass
Index: 1.70
Specific Gravity: 2.99
ABBE: 32
Tints and Coatings
- UV
- Tints
- Photosensitive or Variable tint
- AR Coating
UV Coating
Block UV light to 400nm
Tints
- Glass: Metal oxides added for color
- Plastic: Lenses dyed to color
Photosensitive or Variable Tint
- UV darkens
- IR lightens
AR Coating
- 1/4 wave length thick
- Material equal to square root of lens (
magnesium fluoride )
Tints
- Gray: Neutral, balanced color
- Brown: Reduces blue increases contrast
- Green: Reduces blue and red
- Yellow: Enhanced contrast
- Pink: Reduces blue
Polarized lenses
- Stretched sheet of polyvinyl acetate dipped
in iodine only allows vertically vibrating
light waves to pass through. - Film dyed to desired color
- Laminated or embedded
What are the advantages of polarized sunglasses?
- Decrease driving fatigue
- Water sports
- Snow
- True colors
Younger Optics NuPolar
- The lens has a 99% polarizing efficiency, blocks virtually all glare, and enhances contrast for maximum visual clarity.
- Image wrap: +8.25D Base curve decentered
PAL polycarbonate with NuPolar. - New 1.67 Index
Essilor Xperio Polarized
- Polarized lenses from Essilor, KBco and
Specialty Lens Corp. - 37 Unique Lens design and material
combinations.
Specialty Lens Corp
- New progressive design under the iRx
polarized brand, available in CR- 39,
Polycarbonate, 1.56, 1.60, & 1.67 index
options. - Designed by Essilor
- Smoke, Chocolate, Ash, Carmel, Forest,
Copper, Ruby, Sunflower, Violet, Sunset,
Rose, Ocean & Grass.
KBco
- Wrap Solutions polarized
- +8.25 B.C. Aspherically compensated
- No special surfacing equipment required
- Available in polycarbonate single vision and
EOS wrap progressive. - True Grey, Grey - C & Brown - C
- Kbco.net
Vision - Ease : Coppertone
- The polarized technology eliminates
reflected glare and delivers super UV and
blue light protection to help the wearer
avoid cataracts, macular degeneration, and
premature wrinkles around the eyes. - Polycarbonate grey or brown
- SV, FT, & PAL’s
Wiley X: Fishing & Boating
- Wiley X is one of the few companies that
can prescribe frames with 8 base
curvatures. Now flat prescription frames
are a thing of the past. - Uses only shatterproof polycarbonate
which is the most impact resistant lens
material available. - Patients can locate the nearest Wiley X
dealer with the Wiley X Dealer locator.
Costa Del Mar
- 580 Lenses:
- Polarized glass
- Blue, Green & Silver Mirror, Gray, Copper
- 400 Lenses
- Polarized glass, CR-39 & polycarbonate
- Blue & green, gray, amber, vermillion,
sunrise.
Kaenon Polarized
- Same purpose-built lens tints and light
transmission-level lens innovations that
are available in non-prescription Kaenon
polarized lenses. - SR-91 polarized lenses 1.56 Index 1.15
Specific Gravity 40 abbe. - Anti - reflective treatment applied to front
and rear of RX lens. - All Kaenon polarized frame styles are RX -
friendly, including KORE and the variant
series. - Kore, Variant series and Basis RX lenses
receive front - side flash mirror treatment
and laser engraved logo on front, anti -
reflective treatment applied to rear - side.
Rudy Project
- RX direct in frame interchangeable system
- Rx their favorite Rudy models directly in the
frame. - 2 or 3 RX lenses in different tints to manage
any light condition. Lenses interchange in a
snap, yet stay snugly in place during
sports. - S. V progressive
- Clear, transitions, KBco wraps
Photochromism
- Greek:
- Phos = light
- Chroma = color
- Defines a light - induced, reversible color
change activated by EM radiation. - Discovered late 1880’s
- Can occur in organic or inorganic materials
- Involves a reversible chemical reaction:
- Colorless molecules converted to colored
form that’s reversible. - Activated by UV light
- Colorless molecules converted to colored
Photochromic Lens History Time Line
- 1940’s: Corning Glass begins experimenting
- 1962: Corning Photo Gray glass lenses
released - 1960’s and 1970’s: an array of glass
photochromic lenses - 1974: Fusible photochromic glass
segmented multifocals- Flat tops and round segments
Glass Photochromic Lenses
- Silver halide crystals
- Performance factors:
- Light intensity
- Temperature
- Lens thickness
- Hardening
What year did PPG discover a new family of photochromic compounds - blue pyridobenoxazines?
1983
When did PPG & Essilor partner to form Transitions Optical Inc?
1990
When did Transitions Plus launch?
1992
When did Transitions 3 come out?
1996
When did Transitions Next Generation come out?
2002
When did Transitions V lenses come out?
2005
2008 Transitions VI & 2014 Transitions VII
- Enhanced photochromic performance
across all major lens materials and
designs. - Gets clearer and becomes darker and does
both faster. - Better performance in warm climates.
- UV protection extended to the 400nm level.
Photochromism
A light induced reversible change in color
Factors affecting lens performance
UV radiation and Temperature
Photochromic Lens Manufacturing Processes
- First photochromics were Crown glass
- Photochromic materials are added to the
lens material. - Glass lenses use silver halide crystals
Corning SunSensor
- Distributes photochromic molecules
throughout the lens, allowing a consistent
and effective light response for the life of
the lens. - Available in single vision and progressive
lens designs. - 1.56 Index Grey or Brown
Rodenstock
- In mass photochromic material distributes
photochromic molecules throughout the
lens, allowing a consistent and effective
light response for the life of the lens. - 1.52 plastic ColorMatic Extra SV, BF, and
PAL grey or brown. - Darkens up to 50% in the car
Plastic Photochromic Film Lenses
- Vision Ease LifeRX Photochromic
- Photochromic impregnated film is
positioned between two thin wafers of
polycarbonate. - Available in grey, brown, SV, FT, and PAL
Making Plastic Photochromic Lenses
- Use a photochromic impregnated film
inside the lens.
Photochromic Coating
- Photochromic molecules added to a carrier
medium and coated onto the lens surface. - Corning Sun Sensors HPC
- Made by Polycore Optical USA
- 1.60 & Polcarbonate
- Fast Reacting
Matrix Bonding
- 0.8mm photochromic matrix layer bonded
to front surface of the lens and covered
with an anti- scratch coating. - To avoid damage during surfacing, the lab
must adhere to minimum center and edge
thicknesses.
Kodak Instashades
- The rapid reaction photochromic matrix is
chemically interlocked to the lens substrate
to ensure KODAK InstaShades Lenses have
a long life.
Imbibition
- Photochromic compounds driven 0.15mm
into the front surface. - Molecules become permanently molded
into the surface and part of the lens. - Cannot scratch or peel off
Transbonding
- Some material are not ideal photochromic
substrates. - Applies proprietary surface treatments in a
series of layers. - Help apply transitions photochromic
technology to lens materials previously
considered unsuitable.
Transitions Lenses
- Block 100% UVA and UVB
- Provide UV 400 protection
- Compatible with all major AR treatments
- With AR treatment, they are even clearer
than hard coated lenses. - Available in the most popular materials and
designs.
Transitions Xtra Active
- Darker outdoors in normal and hot temps
- Slight tint indoors
- Activate moderately behind the windshield
- Block 100% UVA and UVB
- Gray activates to green gray color
- Poly, Trivex, & 1.67
Transitions Drivewear
- Responds to visible and UV light
- Provide glare protection through
polarization. - Control light under varying outdoor lighting
condition.
Corning CPF Lenses
- CPF 450: Albinism, Psedophakia
- CPF 511: Macular Degeneration, Cataracts
- CPF 527: Diabetic Retinopathy
- CPF 550: Retinitis Pigmentosa
- CPF 550XD: Achromatism
Fundamental of Light
- Light is created by radiant sources and
emitted in waves. - Light travels from its source in wavefronts.
Antireflective Coating
- Path equals thickness, 1/4 wavelength or
odd multiples. - Amplitude equals top to bottom of wave,
Index of the film must equal square root of
lens material index. - Materials: Magnesium Fluoride, titanium,
zirconium, sodium dioxide - Hydrophobic coating
The EM Spectrum
- Light is part of the EM spectrum
- Creates magnet field around the wave
- Wavelengths from extremely long to
extremely short. - Visible region = a tiny sliver ( 380nm -
760nm) - UV above visible; infrared below this ( both
are invisible)
Wavelengths and Colors
As the eye receives one wavelength or a small grouping of wavelengths, it sees a single color.
Anatomy of a Wave
- Amplitude:
Maxima and Minima - Wavelength
- 0-360 = 1 Wavelength or cycle
Law of Reflection
Angle of incidence = angle of reflection
Reflections and Lenses
- Towards observer
- Towards wearer
What can AR reduce?
- Eyestrain
- Eye Fatigue
- Headaches
- Loss of focus
What percent of computer users suffer from eye strain?
88%
What percent preferred AR lenses compared to hard coated lenses?
86%
What percentage preferred AR lenses for computer use?
62%
What percent preferred AR lenses for night driving?
69.6%
What percent chose AR lenses for visual comfort?
59.8%
What percent AR lenses for reduction of reflections?
71.7%
What percent of wearers would purchase AR again?
98%
Antireflective System
- Combo scratch coat and 9-layer AR
coating per side:
-Include 3 quartz-like layers
-Green, Gold, Purple color
-Hydrophobic layer - ~1% reflection per surface
How long do AR lenses last?
2 years
How scratch resistant is the coating?
- Automated repeatable abrasion test
using Colts Laboratory’s Scratch
Testing Device. - Steel wool pad rubbed against
convex side of lens under 5 pound
weight for 200 cycles.
Abrasion Resistant Coatings
- Inorganic: Evaporating a material
like quartz in a vacuum chamber. - Organic: Chemical mixtures bonded
with lens surface.
List the different abrasion resistant coatings tests
- Bayer Test:
Lens placed in Pan with sand and
moved back and forth. - Tabor Test:
Lens placed on turntable, exposed
to 2 abrasive wheels. - Steel Wool Test:
Steel wool pad attached to arm,
moved across lens surfaces for
standard time and pressure. - Tumble Test:
Tumbles in barrel filled with
abrasive material - supposed to be
equivalent to one years wear.
Three main uses for aspheric curves
- Optical aberration control:
Improved off center optics for RX’s
> +7.00 or -23.00D than spherical
base curve. - Cosmetic:
Allows the use of flatter base curves
while maintaining good optics. - Power change:
Used for progressive addition
lenses.
Tscherning Ellipse
- A graphical representation of the
front surface power as a function of
the total lens power in best form
lenses. - There are two possible solutions,
those that are least curved and
those that are most curved.
What is the least curved portion of the Tscherning Ellipse?
Oswalt Branch
What is the most curved portion of the Tscherning Ellipse?
Wollaston Branch
Vogel’s Formula For Plus Lenses
B.C. = Spherical Equivalent + 6.00
Vogel’s Formula For Minus Lenses
B.C. = (Spherical Equivalent + 6.00) / 2
Base Curve: Aspheric
- The radius of curvature changes
from the center to the edge. - Front curve for Plus RX flattens
edge. - Front curve for Minus RX steepens
toward edge. - Back curve for Minus RX flattens
toward edge. ( Stock lens or special
processing)
Aspheric Advantages
- Reduced lens thickness
- Less bulge for Plus RX’s
- Less magnification for plus RX’s
- Less minification for minus
- Lenses look and stay better in
frames. - More frame choices
- Improved peripheral vision
Atoricity
An extension of aspheric design technology, allowing lens designers to optimize both sphere and cylinder powers.
Atoric Surface
- Asphericity varies for each power
meridian. - Every sphere and cylinder
combination is optimized.
Surfacing
- In conventional surfacing, a
generator grinds away plastic on
back of lens creating rough surface. - Final Ex on back surface is produced
by rubbing against an aluminum
tool and pad in fining and polishing
steps.
Free Form Machining
- A natural diamond-cutting tool
produces a very smooth surface
that requires only light polishing to
create transparency. - Each lens may require over 10
million calculations to generate the
data file for the free forming
machine to create the lens surface. - The computer lens design is exact.
- Control off-axis astigmatism
- Perfect curves for sphere, cyl, and
axis. - Create curves:
-Aspheric
-Atoric
-Progressive
Fitting Aspherics
- Pre adjust the frame
- Dot centers of pupils, measure
height and subtract 1mm for every
2 degrees of tilt or tilt head until
pantoscopic tilt is eliminated before
dotting pupils. - Use pupilometer for mono PD
- Check cut out, prism cant be ground
for decentration.
AO Sola Vizio
- 1.66 index
- Unique atoric design
- Flattened aspheric profile
- Less mag
- AR coated
- -10.00 to +6.00D, 4.00D cylinder
Optima Resolution
- Aspheric front surface
- Atoric back surface
- Polycarbonate
- ECM-9TM Extrusion Compression
Molding - AR coated
- Tantium non-tintable S/R coating
- Tintable S/R coating
Augen: Trinity Double Ashperic
- Front aspherized in 2 meridians
- Semi finished
- Trivex
- +6.00 to -10.00, up to 4.00D cylinder
Wrap around sunglasses
+8.00 Base Curve
Sola Spazio RX wrap lenses
- Proprietary software and processing
techniques. - Based on frame design, degree of
frame wrap and patient PD. - Three different atoric designs to
minimize peripheral blur. - +1.50 to -6.00 sphere with up to
2.00D cylinder - Hard resin or polycarbonate
Ultimate RX Wrap Around
- Sola Contour Optics
- 16.00D base curve with custom
engineered frame. - Near constant vertex distance for all
angles of sight.
