Dispensing - Tints

Question 1

Up to what wavelength can lenses absorb if a UV filter is added to the lenses?

Answer 1

up to 400nm

Question 2

up to what UV filter do
-plastic lenses absorb
hi index lenses absorb?

Answer 2

• plastic: 350nm
• hi-index: 380nm

Question 3

How can glare from bright sunlight, fluorescent lighting or VDU screens be reduced?

Answer 3

with 85% LFT tint or MAR coating

Question 4

How can eyes be protected from infared radiation?

Answer 4

by a tint with high iron content whoch absorbs IR like RayBan G15

Question 5

what are the options of tints for plastic lenses?

Answer 5

• dip dye
• mirror tint
• polarised
• transitions

Question 6

how does dip dying plastic lenses work?

Answer 6

1. plastic lens is dipped into hot dye (93-98 degrees)
2. the longer it stays in there the darker it becomes
3. dye penetrates surface to a depth of approx 1mm
4. can reduce tendancy of lenses getting paler over time by over tinting lenses then placing in bleach for a few seconds

Question 7

what kind of tint is an LTF of 20%?

Answer 7

a light tint as it would let through 80% of light

Question 8

what actually are mirror tints? What principle do they work on?

Answer 8

metallic oxide vacuum coated to the front surface

principle of constructive interference

Question 9

what position must the polarising axis be set to when glazing polarized lenses?

Answer 9

must be set vertically

Question 10

what kind of frames are polarised lenses not good for?

Answer 10

-rimless
-supraframes

Question 11

for polarised lenses, an occupation they are good for and 1 they are not

Answer 11

good for fishermen
not good for skiers

Question 12

what is sensity?

Answer 12

a type of photochromic lens manufacturer

Question 13

what are the disadvantages of polarised lenses for drivers?

Answer 13

can make it difficult to see LCD screens and can also react negatively to certain tints on windshields

Question 14

How do photochromic lenses work?

Answer 14

1. molecules of spiroxazines are embedded into the front surface 0.15mm deep
2. chemical process happens on UV exposure causing molecules to darken to sunglasses shade/ tint
3. photochromic lens remains darkened while exposed to UV and then process reverses once lenses are removed from UV

Question 15

What are the advantages of photochromic lenses?

Answer 15

• reduced costs
• UV protection
• convenience

Question 16

what are the disadvantages of photochromic lenses?

Answer 16

• reaction time from uv to dark can take up to 6 mins which can be dangerous when entering a dark room/ area
• work better in cold conditions
• do not work int he car due to windscreen blocking out UV rays
• do not always go dark enough for those who suffer from extreme high light conditions

Question 17

What are the options for glass tinted lenses?

Answer 17

• solid tint
• equitint
• vacuum coat
• photochromic

Question 18

What is a glass lens solid tint and what does the depth of tint depend on?

Answer 18

• metallic oxides added to molten glass during production
• depends on lens thickness so colour various throughout lens

Question 19

what is the equitint? What is it good for?

Answer 19

1.3mm layer of solid tint bonded to front surface of the main lens

good for high powered lenses as lens will appear same colour throughout

Question 20

what does vaccuum coated glass lens process involve?

Answer 20

• depositing a layer of high refractive index metallic ocide film (n-2-4), usually on the back surface of the lens in a vacuum chamber
• filter reflects away unwanted radiation

Question 21

do transitions work better in warmer or cooler condiitons?

Answer 21

cooler conditions

Question 22

give 7 reasons for dispensing tinted lenses

Answer 22

• Cosmetic/Fashion
• Sunglasses
• Visual Comfort Tints
• Therapeutic and Medical Uses
• Contrast Filters
• Industrial Filters
• Occupational Filter

Question 23

how can grey tints affect facial enhancement?

Question 24

what kind of glasses are graduated tints good for?

Answer 24

varifocals as they keep the lower reading portion clear

Question 25

why may grey tints not be good for facial enhancement ?

Answer 25

they can enhance dark skin around the eyes which can be uncomplimentary for some people

Question 26

what are some positives and benefits of tints being used for fashion?

Answer 26

Positives: - add a fashionable element to the glasses - reduces glare and eye strain - avaliable in various colours and intensities to suit preferences and needs Negatives - colour choice can impact looks e.g. grey may not be suitiable for everyone

Question 27

How do visual comfort tints work and what are they for?

Answer 27

work by filtering out specific wavelengths of light, reducing glare and blocking harmful UV light - minimise eye strain - improve visual experience in varying light conditions

Question 28

give 2 examples of visual comfort tints

Answer 28

anti reflective coating photochromic lenses

Question 29

give a theraputic application for tinted lenses and how this is carried out

Answer 29

- dylexia - tint is determined by a colorimetry test typically following the use of coloured overlays

Question 30

what are contrast filters good for?

Answer 30

sports and driving

Question 31

How do contrast filters work

Answer 31

1. transmit longer wavelengths and absorb shorter ones 2. image sharpens as chromtic aberrations are reduced 3. px has illusion of increased brightness as colour visual nerve cells are hyperstimulated

Question 32

who are industrial filters for and give occupation examples

Answer 32

those under exposure of IR in the workplace e.g. - glassblowers - furnace workers - anyone working with lasers

Question 33

up to what wavelenth does Norville laser protection glass protect?

Answer 33

up to 1100nm

Question 34

What is Blue Barrier 540?

Answer 34

a tint manufactured by BPI which absorbs all violet and blue in the spectrum of light - used by dentists when curing ceramic fillings | only transmits light above 540nm

Question 35

for the didymium optical filter, - what is the highest absorption - what is its function - what are the 3 applicatopns - who is the supplier - what colour are the leses?

Answer 35

- Highest absorption in the yellow region of the spectrum (approximately 560 nm). - enhances contrast between red and green by abosrbing yellow light - helps recognising navigation lights at sea and assists individuals with certain colour vision defects - avaliable as glass lenses from Norville - rose coloured