Frames and Lenses Flashcards
What are 4 types of plastic frame materials? (Regular)
- Cellulose Acetate (Zyl) - most common)
2 Cellulose Propionate - Optyl
- Polycarbonate
What are some pros and cons of Cellulose acetate frames?
Pros
- cheap
- easy to adjust
- lots of colours and patterns
- heat to insert/remove lenses
Cons
- becomes brittle with age
- not suitable for people with latex allergy
What are some pros and cons of Cellulose propionate frames?
Pros
- lightweight- strong
- hypoallergenic
Cons
- cold insert (shrinks with heat)
What are some pros and cons of Optyl frames?
Pros
- Shiny for years
- VERY strong: the only plastic that does not need a metal core
- Hypoallergenic
Cons
- Becomes floppy with heat
- Memory so not readily adjustable
What are some pros and cons of polycarbonate frames?
Pros
- strong for safety and sports
- lightweight
- “Unbreakable”
Cons
- Few colour choices
- Not adjustable
- Low heat
What are 7 types of metal frame materials? (regular)
- Stainless Steel
- Gold
- Silver
- Nickel (Monel)
- Aluminum/Copper aLloy
- Cobalt
- German Silver-Nickel
What are some pros and cons of Stainless Steel frames?
Pros
- lightweight
- usually hypoallergenic
- strong and corrosive resistant
- thin
- typically not marked with pliers
Cons
- made to any grades
What are some pros and cons of Gold frames?
Pros
- one fo the first frame materials
- corrosive resistant
Cons
- soft metal, so frames are usually only gold-plated (not solid gold)
What are some pros and cons of Silver frames?
Pros
- Corrosive Resistant
- Durable
Cons
- Will tarnish
- soft metal
- made to many grades
What are some pros and cons of Nickel frames?
Pros
- Durable, so it is often used as an alloy
- many colours and thicknesses
- Easily adjustable
- Economical
Cons
- Common allergen
What are some pros and cons of Aluminum/Copper frames?
Pros
- Lightweight
- Anticorrosive
- Strong and malleable
Cons
- Cannot solder, so rivets are needed
What are some pros and cons of Cobalt frames?
Pros
- non-corrosive
- strong
- many colours
Cons
- expensive
- difficult to adjust
What are some pros and cons of German Silver-Nickel frames?
Pros
- Strong
- Shiny
Cons
- gets brittle with age
What are 3 types of “hight tech” plastic frame materials?
- Nylon
- Polyamide Polymer→ Kevlar
- Polyamide Polymer→ TR-90
What are some pros and cons of Nylon frames?
Pros
- Almost unbreakable
- Flexible and lightweight
- memory
Cons
- not readily adjustable
- dries out and gets brittle (soak in water 1/month)
- cold insert
What are some pros and cons of Kevlar frames?
Pros
- Impact resistant
- Strong
- Corrosive resistant
Cons
- Limited colours
- Not very adjustable
- Cold snap
What are some pros and cons of TR-90 frames? AKA?
A.K.A. the plastic titanium
Pros
- Lightweight
- Impact resistant
- Many colours both shiny and matte
- Use low to medium heat
Cons
- None!
What are 5 types of “high tech” metal?
- Carbon Fibre
- Titanium
- β-Titanium
- Memory Metal
- Beryllium
What are some pros and cons of carbon fibre frames?
Pros
- durable, thin and strong
- corrosive resistant
Cons
- usually available only in dark colours
- gets brittle
- breaks into shards
What are some pros and cons of titanium frames?
Pros
- very strong and lightweight
- hypoallergenic
- holds an adjustment well
- 30% stronger and 50% lighter than other metals
Cons
- expensive
- difficult to adjust (but holds the adjustment)
What are some pros and cons of β-Titanium frames? How does it differ from Titanium?
Pros
- Strong
- Hypoallergenic
- A little cheaper than titanium
Cons
- memory
β-Titanium is an alloy with aluminum
What are some pros and cons of Memory Metals frames?
Pros
- Lightweight and strong
- Hypoallergenic
Cons
- Difficult to adjust
- Need to adjust and hold in place!
What are some pros and cons of Beryllium frames?
Pros
- Strong
Cons
- VERY expensive
What are the 5 temple designs?
- Library Temple
- Cable Temple
- Extended Temple
- Bowed Temple
- Skull Temple
Describe Library temples
- Straight temples with not downward bend
- Hugs the head rather than curve behind the ear
- Designed to be taken on and off all day easily
Describe Cable temples
- Usually metal ( when made of plastic they are called a riding bow)
- Completely hooks around the ear
- For children and sports
Describe Extended temples
- An extended end piece to allow for smaller diameter lenses
- Can be used with skull, library or cable temples
Describe Bowed temples
- Good for larger heads
- Temples bow out to allow for smaller diameter lenses but comfortable fit around the head
Describe skull temples
- Typical temples
- Bend at the ear crest to fit behind the ear
What are 3 advantages and 3 disadvantages of Crown Glass?
Abbe = 58 n = 1.523
Advantages
- Best Optics
- Stays clear as it ages
- Naturally scratch resistant
Disadvantages
- Heavy (2 times plastic)
- Not as safe (chip and break)
- Doesn’t tint well (the tint goes through the whole lens)
- Very little UV protection
- Lenses become unsafe after they chip/pit after being tempered
What are 3 advantages and 3 disadvantages of CR-39 Plastic?
- Abbe?
- n?
Abbe = 58 n = 1.49
Advantages
- Lighter than glass
- 6x the UV protection as glass
- More impact resistant
- Easily tintable because the tint is only on the surface
Disadvantages
- Easily scratches (softer than glass)
- Still needs UV coating for full UV protection
- Warp, brittle and will discolour with age/UV exposure
What are 3 advantages and 3 disadvantages of polycarbonate?
- Abbe?
- n?
Abbe = 31 n = 1.586
Advantages
- Almost shatterproof
- Lighter and thinner than glass, plastic and trivex
- Natural UV protection ( up to 380 nm)
Disadvantages
- More likely to have chromatic aberration (abbe 31)
- Very soft material
- Gets brittle with age
- Does not tint well
- Low tensile strength (DO NOT use for drill mount)
- Chemical sensitive (acetone)
What are 3 advantages and 3 disadvantages of Trivex?
- Abbe?
- n?
Abbe = 42-46 n = 1.532
Advantages
- Lightest material on the market
- Very impact resistant
- Thinner than plastic or glass
- Tintable
- Good for drill mounts
- Not chemical sensitive
- FULL UV protection
Disadvantages
- Scratches easily
- Not available in all prescriptions
- Harder to keep clean
What are the two methods of tempering?
- Heat Hardex
2. Chemical Hardex
Explain the steps of heat tempering
- The already edge lens is placed into a kiln and is heated close to the melting point
- The inner section of the glass cools slower, but as it cools it wants to contract so this pulls on the already cooled edges
- As the centre pulls on the outer edges it generates the maximum compressive strength/tensile strength
What are some pros and cons to hear tempering?
Pro: Fast process (2-3 minutes)
Cons:
- Cannot mass produce
- Uneven stress causing warpage
- Slightly poorer optics
- Cannot edge after being tempered (this will shatter the lens)
- Spontaneous breakage
- Banding (uneven tinting)
Explain the process of chemical tempering
- Lens blank is placed into molten salt (potassium nitrate) which causes an ion exchange
- The surface tension squeezes the lens as sodium ions are pulled out of the lens and replaced with potassium ions (larger)
- This causes compressive stress
What are some pros and cons to chemical tempering glass?
Pros:
- This process does not need supervision
- Mass production
- Better optics
- Safer (less stress)
- Harder
- No warpage
- No spontaneous breakage
- Re-edgeable
Cons:
- Slow (9-16 hours)
How can you tell if a glass lens is heat tempered of chemical tempered?
Heat - A maltese cross will appear as there is uneven stress when you shine a light on the lenses
Chemical - Dip the lens in glycerine and the edges will glow
What is the relationship between index and scratches?
the higher the index, the softer the lens material and the more easily the material scratches
Define photochromatic lenses
Lenses that change colour/tint when you go outside due to UV/light exposure
Describe photochromatic technology in glass lenses
- Silver halide crystals are placed in glass material
- In light, the silver molecule is excited and loosens from the halide and this causes the lens to darken
- In the dark, the silver molecule relaxes and the lens lightens
What are some advantages and disadvantages of glass photochromatic lenses?
Advantages
- Changes behind a windshield
- Glass changes faster than plastic
- Full UV protection all the time
- Rely on both UV and light
Disadvantages
- *Temperature sensitive (goes darker in the cold) ∴ inconsistent
- *You always have to replace both lenses
- Elevation sensitive
- Over time the lenses become darker (even in the clear stage)
- Require seasoning (change 10 times before they reach full darkness)
- Banding and raccooning (the molecule is throughout the material)
- Leads to lazy pupil constriction over years
Describe photochromatic technology in plastic lenses
ISN technology
- When UV is absorbed by ISN the molecule breaks in half to create a hinge
- Half the ISM rotates to a new position and is able to absorb visible light and causes the lens to change colour
What are some advantages and disadvantages of plastic photochromatic lenses?
Advantages
- Clearer inside than glass
- Full UV protection
- Readily available
- Colour variety
- No seasoning
- No banding (it is just a coating rather than through the lens)
Disadvantages
- Most do not work well in the car (UV needed)
- Become less effective with age as the hinge becomes fatigued
- Temperature sensitive (altitude and cold bright days)
Describe polarized lenses
A sunglass lens design that eliminates glare coming from light that bounces off a horizontal surfaces.
A filter of Polyvinyl Acrylate
What is Polyvinyl Acrylate?
A filter that is used for polarizing lenses. When this filter is stretched in one direction the laminate filter becomes polarized
What are the two ways to make polarized lenses?
- Laminate design - Two clear lenses are glued together with PVA filter sandwiched between
- Mold Design - Suspend PVA within a mold and pour the lens material around it (the lens does not separate this way)
What are the advantages and disadvantages of polarized lenses?
Advantages
- Cuts glare
- Boating and fishing
- Downhill and cross country skiing
- Clearer/sharper vision and enhances colour contrast
- Faster reaction time
- Eliminates eye strain
Disadvantages
- Pilots cannot wear the
- Can interfere with LCD screens
- Bad for aerial skiing and mogul skiing
- Not available as a clear lens
Define Photochromatic Polarized lenses
Polarized sunglass lenses tat get darker as light/UV increases
What are the benefits of Pink lenses? What are they best used for?
- Sharpens images
- High contrast
- Increases depth perception
- BEST for water/snow activities and night driving
What are the benefits of Grey lenses? What are they best used for?
- Best filter of light
- Does not change colour perception
- BEST for bright days and DEEP water activities
What are the benefits of Brown lenses? What are they best used for?
- Sharpens images
- Reduces eye fatigue
- Good everyday lens, very versatile
- BEST for overcast days
What are the benefits of Yellow lenses? What are they best used for?
- Increases contrast
- Enhances images
- Enhances low lighting (night, fog and haze)
What are the benefits of Green lenses? What are they best used for?
- Good “all-purpose” tint
- Natural filter of infrared
- BEST colour contrast
- Pilots light green (G-15)
Describe True-Colour Tints
The tint is through the material, not just a coating, and they are made with metal oxides. This type of tint can cause banding which is available on both glass and plastic lenses
Describe SurfCoat Tints
A tint (on glass lenses only) that is only on the surface that is used to eliminate the banding problem often seen in glass
How can you recognize SurfCoat lenses?
A gasoline-like hue on the BACK surface of the lens. This is due to internal reflections. It looks like a backside AR but is is multiple colours
Describe ToneLite Glasses
A rose/flesh-coloured lens that was designed to eliminate glare that comes of artificial lights. It came in 3 intensities and was only available in glass lenses. This lens provided UV 400 proteciton
What is the Protective Lens Series? What are the 4 lenses and who are they good for?
A Lens designed to protect against UV light and Blue Light
PLS 400- Light orange/Amber - protects UV only
PLS 530- orange - 95-99% UV + blue light up to 530 nm (dentist curing, albinism)
PLS 540- brown - 95-99% UV + blue light up to 540 nm (divers, pilots, mountain climbers)
PLS 550- red - 95-99% UV + blue light up to 550 nm (AMD, glaucoma, welders)
Describe Antifog
A coating/treatment applied to a lens that helps prevent fogging
What are CPF lenses?
Corning Protective Filter - A photochromatic lens that is made differently (the lens is fired on the front surface to reduce the silver halide crystals near surface). This lens is designed for extreme photophobes
Describe Mirror coatings
A coating applied to a lens to give it a mirror-like finish.
What are pros and cons to mirror lenses
Pros
- Reflects incoming light so therefore there is less light reaching the eye (next best thing to polarized lenses)
- Gives great contrast and reduces eye fatigue
Cons
- Easy to see scratches
What 4 prescriptions benefit most from digitally designed lenses?
- High sphere
- High cylinder
- Oblique Axis
- High adds
What is wavefront technology?
A tool to measure hot a wave of light passes through a lens to determine what aberrations come out on the other side - it help determine how to correct the proper aberrations
How do they implement wavefront technology?
They use specific front and back curves to cancel out aberrations
What is the difference between digitally molded and digitally surfaced?
Molded - Lens is poured into a mold
Surfaced - Diamond porter pokes into the back surface to customize the back curve
Back surface vs front surface digitally surfaced
Optics are better when they are closer to the eye so Back surface Digital > Front surface Digital
What are some pros and cons of digitally surfaced lenses?
Pros
- Higher (spherical and coma) and lower (Rx itself) aberrations are eliminated
- Better night driving
- Thinner and lighter lens
- Sharper VAs in 360º of the lens (NOT no distortion)
- Better contrast (4K TV)
- Wider field of view in PALs
- Faster adaptation to PALs
- Less eye fatigue
Cons
- Needs more precise measurements (Position of wearer, face form, vertex, pantos…)
- Special order - takes longer to receive
- Harder to verify in the lensometer
- Requires more precise frame adjustment
