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Ophthalmic Optics Block 11 > Tints And Coatings > Flashcards

Tints And Coatings Flashcards

1
Q

Types of coatings

A 
Oil repellent 
Dirt repellent 
Water repellent 
Anti static 
Anti reflective 
Scratch resistant 
UV
Smudge repellent
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2
Q

Repel water, preventing the formation of water spots

A

Hydrophobic

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3
Q

Resists smearing from facial or skin oils

A

Oleoplastic

  • aka lipophobic
  • smudge resistant
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4
Q

Reduce attraction of dust

A

Anti-static

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5
Q

Eliminates the condensation of moisture on lenses that cause fogging

A

Anti-fog

-eyeglasses fog up when coming in from the cold

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6
Q

Fog free, coating applied to lenses before they are cut to frame

A

Opticote

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7
Q

Essilors fog free coating

A

Optifog

  • drop applied to each side of the lens, then wiped
  • lasts for a week
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8
Q

A coating applied to a lens that does not interfere with how the lenses function, but creates a permanent bond with the lens that reduces the incidence of the hairline scratches common to plastic lenses

A

Scratch resistant

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9
Q

What lens material is scratch resistant

A

Glass

-plastics are more fragile and a scratch coating is necessary

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10
Q

How is scratch resistance coating applied

A

By dipping or spin coating to create a uniform, thin coat

  • dipping: lens immersed in bath of coating solution
  • spin coating: liquid coating dropped on center surface and rotated rapidly

Coating must be cured to strengthen adherence and promote durability

  • baking (hours, higher quality)
  • UV curing (minutes, lower quality)
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11
Q

Which method of curing scratch resistance is the best quality

A

Baking

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12
Q

Which method of curing scratch resistance is of lowest quality

A

UV curing

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13
Q

A thin layer or series of layers of material applied to the surface of a lens for the purpose of reductions unwanted reflections from the lens surface and thus increasing the amount of light that passes through to the eye

A

Anti-reflective coating

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14
Q

Benefits of anti-reflecrive coating

A
  • better light transmission (transmission booster)
  • better vision in al lighting situations (especially low light, night driving, computer use)
  • reduces eye strain
  • cosmetic benefits
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15
Q

How do antireflective coatings allow more light to get through a lens

A

Eliminating reflections from front and back surfaces

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16
Q

The _____ the index of refraction, the more light that will be reflected from the surface

A

Higher

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17
Q

AR coatings usually consist of multiple layers of

A

Metallic oxides

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18
Q

Single layer of metallic oxides in AR coatings

A

Reduction in reflection only optimized for a small wavelength range (purplish)
Usually midrange-green

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19
Q

Multiple layers of metallic oxide in AR coatings

A

More effective over entire visible spectrum

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20
Q

How do the layers of AR coating go

A

Alternate between high and low index of refraction, thus the more layers, the more reflections that are neutralized

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21
Q

How is AR applied

A
  • vacuum deposition technology
  • clean lenses are inspected for visible and microscopic surface defects (hairline scratches, lint, smudges can cause defect)
  • multiple washing and rinsing baths
  • air drying and heating to remove unwanted moisture
  • lenses loaded onto special metal racks so they are held securely but with lens surfaces exposed and put into coating chamber
  • chamber sealed and air is pumped out of chamber to create vacuum
  • while lens racks rotate inside the chamber, a beam of electrons is focused onto a series of metal oxides in separate compartments
  • when the coating materials are bombarded by electrons, they are vaporized and adhere tot he surfaces of lenses
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22
Q

The layer of AR coatings

A

Microscopically thin and uniform

  • 0.2-0.3 microns thick
  • faint residual color (usually green or blue)
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23
Q

How much light in general is transmitted from lenses

A

85-96%

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24
Q

How much light can be transmitted through an AR coated lens

A

98-99.5%

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25
Q

What materials is it recommended to use an AR coating for

A

Polycarbonate and high index

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26
Q

What type of lens is AR coatings preferred in

A

Aspheric lenses due to flatter curves that often cause more noticeable reflections

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27
Q

Sources of blue light

A

Sun, artificial sources like computers

28
Q

Is all blue light bad?

A

No, a little bit is beneficial in regulating our bodies’ internal biological clocks

29
Q

Blue-violet light and eyes

A

Harmful to the eyes, also a risk factor for ARMD

30
Q

How much blue light can pass through the cornea and lens and get to the retina

A

Nearly all of it

31
Q

What coatings can filter out blue light

A

AR

  • Hoya recharge EX3
  • Crizal Prevencia no glare
  • coating is designed to selectively block the harmful types of blue light
32
Q

UV coating

A

Blocks UV rays from damaging the eye

-invisible dye

33
Q

UV exposure can cause

A

Cataracts
Retinal damage
Photokeratitis

34
Q

Good UV coating

A

Less than 5% UV rays pass through

35
Q

Best UV coating

A

2% or less of UV rays pass through the lens

36
Q

UVA

A

320-400nm

37
Q

UVB

A

290-320nm

38
Q

UVC

A

100-290nm

Absorbed by the ozone layer

39
Q

How do you remember the severeity of the different types of UV light

A

A is alright
B burns
C cills (kills)

40
Q

Materials of UV coating

A
  • All of the common lens materials absorb UVB
  • polycarb and trivex absorb UV radiation (treatments unessecary)
  • CR-39-must add UV dye to lens
  • crown glass needs it to
  • hi index plastics: most have built in
41
Q

Lenses that darken on exposure to light, most commonly UV radiation

A

Photochromic lenses

42
Q

How do photochromic lenses work

A

-when exposed to UV light, photochromic molecules being to change in structure. This reaction causes the lens to darken

43
Q

Transitions chromea7

A

Formulation of dyes on the surface of the lens that are made up of molecules that constantly recalibrated as light changes

44
Q

How are the photochromic molecules added to transitions

A

Add through imbibing Uuses heat to draw dye into lens) or trans-bonding (for lenses that do not imbibe, puts on lens surface)

45
Q

Problems with photochromic lenses

A
  • car windows block nearly all UV
  • temperature dependent: darken less at higher temps, more in the cold
  • red light infrared radiation makes the lens return to its lighter state-darken more when skiiing, less at the beach
  • cold, sunny day, take longer to fade when going indoors
46
Q

Photochromic lense block ______ of UV rays without need for an added UV lens treatment

A

100%

47
Q

Photochromic lenses plus AR coating

A

Enhances visual clarity and comfort without reducing the sun reactive performance
-AR can actually increase the lenses sensitivity and decrease reaction time

48
Q

Optimal balance between darkness, clarity, and fade back speed (darken in random patterns)

A

Transitions signature

49
Q

Variable polarization as lens darkens (darken and align)

A

Transitions vantage

  • until recently, polarization was static film embedded in a lens
  • now, lenses contain molecules that darken with UV light and also align at a proper angle in the lens to become polarized
50
Q

Darkest lens, even at high temps

A

Transitions XTRActive

-responds to UV and natural light

51
Q

Polarized and the color and density change in brighter conditions

A

Transitions DriveWear

  • works in the car
  • low light levels (green yellow)
  • Higher light levels (dark red/brown)
52
Q

Additional things about transitions

A

Comes in multiple colors

Helps protect against blue light

53
Q

Mirror coating

A
  • fashion and function
  • solid mirror: high density of color, higher % of reflectance
  • flash mirror: hint of color
  • can absorb from 5-65% more light than non-mirrored surfaces
  • golf, skiing, snowboarding, hunting, fishing, etc
  • reduces glare
  • easy to clean
  • repell moisture, fingerprints, and smudging
  • avaiable on polarized, photochromic, clear, or tinted lenses
54
Q

Worn for cosmetic appeal, visual comfort, protection, or a combination of all three

A

Sunglasses

55
Q

Cosmetic tints of sunglasses

A

Light

Usually transmission of 80-90%

56
Q

Comfort and protections sunglasses

A

10-20% transmission

  • transmittance lower than 15%-back surface reflection could be troublesome
  • remember, 4% ore more of light is reflected at each surface
  • AR coating eliminates glare from sunlight reflecting into your eyes from the back surface of tinted lenses (usually applied to back surface only because there is no cosmetic or visual benefit to eliminating reflections from the front surface of dark tinted lenses
57
Q

Sunglasses tints darker than ___ should be avoided as per ANSI

A

8%

58
Q

Light reflected from secular surfaces can be intense and can obscure objects behind or below the surface. These are lenses that substantially reduce the intensity of these reflections

A

Polarized lenses

59
Q

Disadvantage of polarized lenses

A
  • reduces the ability to identify changes in terrain or identify ice
  • expert skiers lean from side to side resulting in head tilts of more than 30 degrees, causes changes in brightness of snow, dangerous and nauseating
  • can wash out texture of grass making greens difficult to read
  • commercial pilots
60
Q

Consistent color and depth over the entire lens, ranges from barely visible shades to dark shades

A

Solid tints

61
Q

Variable color throughout the lens, usually darker at the top, gradually becoming lighter at the bottom

A

Gradient tints

62
Q

Contains two colors, generally darker or greater depth of color near the top, melding into a second, lighter color near the bottom of the lens

A

Double gradient tints

63
Q

Glass tinting

A

Tinted by mixing metals directly into the glass, absorptive density is related to thickness of the lens, thus coatings or laminate is preferred

64
Q

CR39 tinting

A

Can be dipped into a solution that dyes the lenses

  • longer exposure: darker tint
  • lens cab bleached and retinted
  • fading can occur over time
65
Q

Polycarbonate and tinting

A

Material is impervious to dye so the scratch resistance coating is dyed instead

66
Q

Trivex and tinting

A

Tintable

67
Q

Hi index and tinting

A

Tint more slowly and can require special processes

Ophthalmic Optics Block 11 (4 decks)

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