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DISPENSING > Tints > Flashcards

Tints Flashcards

1
Q

Why do we dispense tints?

A
  • To provide protection from ultraviolet light-
  • To provide protection from glare (disability and
    discomfort) - glare is any light causes discomfort- which causes watery eyes
  • To provide visual comfort
  • Therapeutic and medical
  • Contrast filters- increasing contrast of objects so can see clearer for e.g in a sport like a football use a green tint etc.
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2
Q

Who can benefit from a tint?

A

-a patient that could have early signs of cataract- which elevate their discomfort.

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3
Q

What do tints protect against?

A

certain wavelengths of light such as infrared- which can be damaging to the eye.

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4
Q

Why do we need protection from the different wavelengths of light - UVA ?

A

linked to cataracts and retinal damage - deeply penetrating

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5
Q

Why do we need protection from UVB?

A

linked to cataracts1 and photokeratitis

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6
Q

Why do we need protection from the visible spectrum ?

A

can cause disability and discomfort glare

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7
Q

Why do we need protection from Infrared ?

A

800+nm causes heat cataract and retinal/choroidal burns

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8
Q

Do all sunglasses have UV protection ?

A

No

-UV is a seperate clear coating and you can then go onto adding a tint to it as it is not always provided.

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9
Q

Why are we more concerned about UV coating a tinted lens?

A

-pupil size increase due to dark tint and more light is let into the eye- change the ocular dynamics of the eye

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10
Q

What can the amount of light entering the eye be altered by ?

A
  • absorption

- reflection

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11
Q

What are mirror coatings supplied with?

A

Supplied with a dark tint to prevent the wearer seeing themselves in the mirror coating.

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12
Q

What do mirror coatings do?

A
  • they have Tint depth which also influences the amount of reflection
  • they Don’t wear well- can easily be scratched affecting them
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13
Q

What do the mirror coatings protect from?

A

-Protection from absorption and reflection

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14
Q

How can you describe the tint?

A
  • State the tint by colour
  • Depth in percentage
  • Light transmission factor (LTF) - FOR how light or dark you want the tint to be so by telling how much light you want transmitted through from this factor
  • Absorbance (ABS) - to tell how much light is absorbed by the lens
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15
Q

Is an 85% LTF lens light or dark?

A

light lens - letting 85% of light through

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16
Q

What is the equivalent ABS?

A

15%

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17
Q

What colour tint does a patient choose?

A 
-To enhance contrast? 
Drivewear
Sports tints
-Personal preference? 
-Cosmesis?
Frame choice
-Protection
 Certain colours provide protection
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18
Q

What is the colour of the tint for?

A

the light that is letting through the lens

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19
Q

What does a transmission chart do and tell you?

A

uses spectral anomaloscope which plots the transmittance of radiation at each wavelength

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20
Q

Why is a N tint good?

A
  • filter out all wavelengths roughly the same they don’t distort colours much whereas a contrasting tint will.
  • So when a patient sees through them there is no distortion
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21
Q

What is a N tint?

A

a neutral tint which is grey

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22
Q

Who is a N tint good for ?

A

drivers- don’t want traffic light colours being distorted

-Architectures

23
Q

What tints are available?

A
  • Fixed
  • Graduated
  • Photochromic
  • Polarised
24
Q

What are fixed tints ?

A
  • Same colour throughout the lens

- tint absorbs 1mm into the material - just front surfaces

25
Q

What are the methods of tinting fixed tints?

A
  • Plastic- dip dying

- Glass- solid or laminated

26
Q

How do we tint the fixed tints in a glass material? (2 ways)

A
  • Solid - the tint is introduced tot he lens when it’s molten- a tint is solid throughout the material/ lens
  • if want green tint - iron added to the molten mix
  • Laminate the lens- a laminated tint is a thin sheet which is laminated or vacuum coated onto one surface of the lens- a tint is only one surface of the lens.
27
Q

What do we do when deciding between a solid and laminated tint?

A

Lamberts Law - thinking about the absorption of the material is proportional to its thickness - which means the thicker material the darker the tint

  • If have patient which is -8 = laminated is better-
  • plano lens- better to have solid.
28
Q

What is a solid tint?

A

dispersed in the whole lens/material

29
Q

What is a laminated / equitent tint?

A

only at one surface of the lens.

-not affected by tint at all - equal across the lens

30
Q

What is a graduated tint ?

A

Can be single or dual coloured.

  • They are darker at top graduating to a lighter colour at the bottom.
  • Change in gradient
31
Q

Why is the top darker and the bottom lighter in a graduated tint an advantage?

A

better for an elderly patient who needs reading glasses

32
Q

What is a photochromic tint?

A
  • Darken due to the energy provided by UV.- use energy to alter the structure- when hit UV light turns dark
  • Darken quicker than they return back to light - on a sunny day will turn dark MORE and less UV means less dark.
  • No separate sunglasses required
  • Tint variable
  • Temperature dependent- work better in cold environments than hot
  • Full UV400 protection - if remove this will limit how it works - not as well
  • Less reactive behind a UV filter- e.g. car windscreen.
33
Q

What benefits and advice do you think you should give your patients regarding
 Darken quicker than they return back to light

A
  1. tell patient first so they know that when going from inside to outside the darken quickly whereas going from out to in they take longer to turn colour.
    - explain to the patient as they might think it’s faulty
    - might be a health and safety hazard - if walking straight in - wont be able to see so suddenly.
    - care when walking into buildings
34
Q

 No separate sunglasses required

A
  • save money

- conviencince - no swapping glasses

35
Q

 Tint variable

A

comfort at all light variables

36
Q

 Less reactive behind a UV filter- e.g. car windscreen

A
  • get glare - better outside the car
37
Q

 Less reactive behind a UV filter- e.g. car windscreen

A
  • better outside the car

- may not get as dark when driving

38
Q

 Residual colour with age

A
  • older styles they get old after time (get yellow tint after a while ) - may affect vision in darker conditions.
39
Q

What can photochromatic lenses be made in ?

A

-Glass- which contain
Silver halides- separate when activated by UV - when separated they go darker and recombine and get lighter
Equi-tint can be used on high prescriptions
-Plastic- use
Pyrans and oxazines in the 100-150 microns of the front
the surface of the lens
Molecules rotate on activation by UV- don’t split and as they rotate they become darker

40
Q

Why Polarised lenses?

A
  • Unpolarised light- light which vibrates in all directions
  • Polarised light- it maintains in the one direction- which can cause glare and mirror effect
  • Brewster angle- if angle between the refracted and reflected beam is 90° then the reflected beam will be completely plane polarised.
41
Q

Why is polarised light not good?

A

can cause glare and mirror effect e.g when driving

42
Q

What is polarized light?

A

polarized in the plane parallel to the
reflecting surface
e.g surface of water

43
Q

How can we polarise lenses?

A
  • Axis of the filter set vertical
  • BS tolerance 5 degrees
    -Stretched iodine crystals
    -darker tint more polarisation occurring
    -
44
Q

How can we tell our patient is wearing a polarised lens?

A
  • do that by thinking about the effect of holding up another polarised lens in front of them
  • if you have 2 polarised lens - it will let some light through - the picture will be less clear- contract reduced by still able to see the image
  • if by rotating the filters at right angles to one another - block both vertical and horizontal meridian- won’t see a image
45
Q

What are IR lenses?

A
  • need to use with glass lens
  • Exposure from sun, furnaces and with explosions!
  • Linked to heat cataract, retinal and choroidal lesions
  • Cant protect with CR39
  • Rayban G-15- ferrous oxide- green tint - glass lens
46
Q

UV light exposure ?

A

-Should protect eyes all year round not just in summer or winter.

47
Q

UV damage to the eye can be reversed?

A

No

48
Q

Do you need to wear sunglasses on a cloudy day

A

Yes

49
Q

Are children more vulnerable to UV ?

A

Yes

50
Q

Do darker tinted lenses provide more UV protection?

A

No

51
Q

Do all sunglasses offer UV protection?

A

No

52
Q

Are your eyes more sensitive to UV than your skin?

A

Yes

53
Q

IS UV levels are higher in tropical areas?

A

Yes

DISPENSING (19 decks)

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