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DISPENSING > protective eyewear > Flashcards

protective eyewear Flashcards

1
Q

what are we protecting our patients against?

A
  • penetrating trauma

- chemical burns ( alkali or acidic )

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2
Q

what is impact resistance?

A

the ability of a material to withstand a high force or shock applied to it over a short period of time

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3
Q

how are materials tested?

A
  • materials are tested with the drop ball test and graded in terms of impact resistance
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4
Q

what is the affect of elasticity?

A
  • the elasticity of material is what give the material its impact resistance
  • elastic material is able to absorb some of the shock/force that hits it and lens doesn’t break
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5
Q

how should the frame and lens be ?

A
  • the frame needs to be loose enough that if the lens is flexing during this period of elasticity that its got somewhere to go
  • lens isn’t glazed too tight
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6
Q

what are some health and safety regulations?

A
  • BS EN 166:2002 personal eye protection : specifications
  • BS EN 167:2002 personal eye protection: optical test methods
  • some regulations for sport
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7
Q

what is CE mark ?

A

shows that product is meeting all European standard for health and safety

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8
Q

what are types of protective eyewear ?

A
  • spectacles that are glazed with prescription
  • some can be worn on top of spectacles ( temporary measure )
  • googles ( protect around ocular area ) - can also be ventilated
  • visors - protect the whole head
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9
Q

A screw comes out of the side of a PX safety glasses that he uses for work and asks to put a new one in - what do you say?

A

no, as this will void the manufacturer guarantee

- you need to send back to manufacturer who will re-test the unit and ensure that its meeting standards

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10
Q

what are lens marking?

A

lens markings show that if a lens has met standards but only found if applicable

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11
Q

what are examples of lens markings?

A 
. scale number ( filter lenses )
. manufacturers mark - always relevant
. optical class
. mechanical strength symbols
. field of use
. scratch resistance
. resistance to fogging
. radiant heat
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12
Q

what are some examples of frame markings?

A

. frame should always be marked - this is because frame also has standards

  • manufactures mark
  • appropriate European standard number EN166
  • field of use - intended use
  • mechanical strength
  • CE mark
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13
Q

what is protective eyewear considered as ?

A

considered as a single unit- must be tested as such

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14
Q

what are scale numbers?

A
  • higher numbers= darker filters

- consists of code number and a shade number

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15
Q

what is optical class

A
  • 1,2 or 3 - indicates the optical quality of the ocular
  • how close the prescription is what is should be
    1= in tolerance with what the prescription is expected to be . +/- 0.66 D
  • as numbers get bigger tolerance is lower
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16
Q

what is mechanical strength ?

A
  • looks at impact resistance
    e. g bearing test
  • can be marked with various codes
  • most safety spectacles are marked with an S or F
  • S= increased robustness
    e. g. CR39- not very tough
  • F= low energy impact
    e. g. polycarbonate
  • B= medium energy impact
    e. g. goggles
  • A = high energy impact
    e. g visors or face shield or some goggles
17
Q

what is field of use?

A
  • what spectacles are going to be used foe
. resistance to surface damage
. resistance to fogging
. liquid droplets/ splashes
. large dust particles
. circuit electric arc
. gas/fine dust particle
. molten metal/ hot solids
18
Q

what does filed of use depend on ?

A
  • occupation

- work place assessment - what risks are in the work

19
Q

what should safety lenses have ?

A

safety lenses must be resistant to impact - requires a certain centre thickness to allow an impacting particle to be deflected
- type of thickness depends on material and what is being used for and how its being made tough

20
Q

what materials make a good safety lens material?

A

polycarbonate-
trivex-
glass - must be treated to meet S standard

21
Q

what are the pros and cons of using plastic lenses as protective eyewear?

A
  • more elastic than crown glass
  • impact resistance depend on material
  • impact resistance is affected by coating
  • CR39 can break intro hooked shards
22
Q

what are pros and cons of using glass as protective eyewear?

A
  • untreated is not suitable for protective lenses
  • can be heat or chemically toughened
  • laminated
23
Q

what are pros and cons of using trivex as protective eyewear?

A
  • higher v value compared to polycarbonate
  • UV cut off to 400nm
  • tinting not possible
  • good chemical resistance
  • n=1.54
  • ## lowest specific gravity
24
Q

what is a compression envelope ?

A
  • outside of the lens is put into compression - molecules at the lens surface closer together compared to the centre
  • allows lens to become stronger
  • heat and chemical toughening both produce compression envelopes
25
Q

what does force cause in an untreated glass?

A

untreated glass- force causes compression at blow and release tension on the other side

26
Q

what does compression result in a treated glass?

A
  • compression results in point opposite impact remaining in compression
  • treated glass remains okay
27
Q

what does damage to surface do to compression?

A

damage to surface reduces compression

28
Q

what are the two main methods of toughening a glass lens ?

A
  • heat toughened

- chemically toughened

29
Q

how is heat toughening carried out?

A
  • lenses must be glazed before toughening
  • requires a minimum centre/edge thickness of 2.4 mm
  • lens is heated just below melting point 650 c
  • thicker lens= heated longer
  • variable heating time
  • outer glass cools more rapidly than centre
  • if it does smash then blunt pieces
  • rejection rate compared to chemically toughened
  • can be recognised by Maltese cross on a polarising filter
30
Q

how is chemical toughening carried out?

A
  • lenses must be glazed before toughening
  • lenses placed in 440c molten potassium nitrate bath for 16hrs
  • ion exchange occurs between potassium ions in the bath and smaller sodium ions at the lens surface
  • thin and uniform compression envelope created. no minimum lens thickness required- greater impact resistance when compared to heat toughened
  • no identification possible
  • expensive equipment required
31
Q

what is compression envelope caused by ?

A
  • caused in difference in cooling between the surface and centre
32
Q

what should you remember when supplying protective eyewear?

A
  • if protective eyewear is supplied as industrial prescription protective eyewear then the employer is required to assess the workplace risk
  • you need ti supply to the company order form
  • if you do perform a workplace assessment you must keep detailed case records of the assessment

DISPENSING (19 decks)

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