LAW; u r getting there. Flashcards
what are the types of eye protectors?
- spectacles with or without side shields
- moulded eye shields
- box type googles
- cup type googles
- welding helmets
- face shields
- hand held welding shields
- face masks
what are the characteristics of safety spectacles?
- not suitable for dust, gases, molten metal, hot solids, liquid droplets or splashes (BS EN 166)
- can be made to fit well
- available in plastic frames-safer than metal
- available in metal frames:
- –more damage when impacting on face
- –pads cause injury to the nose
- –screws work loose
characteristics of safety spectacles with side shields?
- must be transparent and not discolour
- injection moulded are best, as they do not wrap to leave gaps
- polycarbonate material ideal
- may be perforated for ventilation
characteristics of moulded eye shields (afocal one-piece, wrap around)?
- moulded from single piece of polycarbonate
- great for emmetropes
- usually only one size
- often supplied by employer-but lack of fitting.
- employees’ typical complaints:
- –restricted field of view
- –slight magnification effect
- –reflections
- –peripheral displacement effect
characteristics of googles-cup type?
- housing made from PVC and tight fit
- good for flying particles such as metal,dust, etc
- suitable for welders
- adjustable nasal fitting
- screw rim to allow for glazing
- large bridge aprons to protect the nose are available
- disadvantages:
- –cannot be worn over spectacles
- –poor ventilation
- –uncomfortable
- –poor peripheral vision
characteristics of box-type googles?
- normally made of PVC, good fit
- one piece lens: polycarb/cellulose acetate or possible toughened glass
- can be worn over spectacles
- well ventilated, lightweight
- wide field of view
disadvantages:
- –nasal fitting not adjustable
- –replacing one-piece lens
characteristics of face shields?
- good for protection against splashes and flying particles
- headband-supported vision that cover the face and neck
- easily worn over specatacles
- excellent FOV
- polycarbonate/ cellulose acetate
- can be handles for welding screens
- motorbike helmet, security guards etc!
characteristics of helmets,
- mostly for welding
- protection against intense heat and splatter
- contains filter for radiation protection
- most have a cell which darkens to welding density as soon as the arc is struck
- sometimes have own air supply as gases from welding rods are toxic
what are the lens materials for eye protectors?
- Glass
- heat-thoughened
- chemically-thoughened
- laminated - Plastic
- PMMA (perspex)
- CR39
- Polycarbonate
- Trivex
- Cellulose Acetate
What are the characteristics of heat-toughened glass?
- crown lens placed in furnace at 637’c for 50-300s
- lens cooled rapidly (cold air)
- sudden cooling creates compression at surface and tension within lens mass- ‘compression envelope’
- quick and cheap process
DISADVANTAGES:
- high plus powers require prolonged heating
- lenses will be thicker
- scratches reduce impact resistance
- photochromic lenses do not work well if toughened
- strain tester pattern (maltese cross)
characteristics of chemically toughened glass?
- more popular in US
- compression coat formed by chemical process
- preheat lens and immerse in KNO3 at 470’c for 16hours
- large K+ ions exchanged for smaller Na+ ions in glass- 100microm compression coat applied
- thinner than heat-toughened but greater impact resistance
- all lenses take the same time to toughen
- no warping
- expensive process
- hard to tell when material has been toughened
What are the results in breakage of toughened glass?
- radial fracture pattern
- sometimes concentric cracks
- only a few splinters formed
- fragments tend to stay in the frame
what are the characteristics of laminated glass?
- two layers of crown glass with inner layer of plastic material
- impact resistance only slightly higher than crown glass
- supposed to stick to plastic if it shatters-not always
- silvers from back may come off into eye
characteristics of plastic materials?
- greater impact resistance
- fragments tend to be large and blunt
- 50% weight cf glass
- some powers will be thinner in glass, as no need to thicken for impact resistance
- withstands molten metal and hot sparks better, as metal does not fuse with surface
- less condensation (lower thermal conductivity)
- greater Uv protection than glass
disadvantages:
- easily scratched
- hardcoat reduces impact resistance
why do we need eye protectors?
to defend against:
- molten metals and hot solids
- gases
- dust
- impact of different severities
- optical radiations
- droplets and splashes
characteristics of PMMA & CR39?
- PMMA = ICI perspex and now largely replaced by CR39
- CR39 greater impact resistance, but sharper fragments.
- both suitable for eye protectors
- CR39 can be tinted unlike PMMA
characteristics of polycarbonate?
- high impact resistance
- very soft
- quartz coating often used but can reduce impact resistance from 224ms to 152ms
- good for children’s spex
- cracks on impact
- no warping or chipping
- very lightweight
- refractive index: 1.586
- absorbs UV
- accompanied by colour fringes in periphery
what are the characteristics of trivex?
- highest impact resistance (low energy impact grade)
- unaffected by most common chemicals and solvents
- lightweight and thin
- V value: 45 (reduced chromatic aberration)
- refractive index: 1.53
- high tensil strength make it resistance to cracking
- 100% protection against UV
- good for children’s spex
what are the characteristics of cellulose acetate?
- only used for basic eye protectors due to relatively poor impact resistance
- good resistance to chemicals
How to test the resistance?
- impact resistance
- influenced by
- ->scratches on lens
- ->size and speed of missile
- ->lens thickness
- ->lens material
* CR39 more impact resistance than glass
* heat more impact resistance than chemically toughened glass
* impact resistance improves with lens thickness and curvature - surface hardness
- a thinly coated (5microm) polycarbonate lens is superior to an uncoated CR39 lens - chemical resistance
- glass lens resistant to most chemicals
- plastics can craze but CR39 has relatively good resistance - thermostability
- polycarb & PMMA are prone to distort more radily than glass - resistance to hot particles
- glass easily pitted as hot particles fuse with glass material
- plastics do not pit easily due to elasticity of surface when heated. - radiosensitivity:
- if particles penetrate the eye it is helpful if they are visisble on x-ray
- glass can be seen if > 0.5mm
- plastics very hard to fine - flammability
STANDARDS AND REGULATIONS:
- CE mark
- most PPE must be certified with 3. things: independent insoection, basic safety requirements, CE marked
- illegal for suppliers to sell PPE without the CE mark - includes all spectacle frames - British Standard (BS)
- health and safety executive (HSE) publish guidance on PPE regulations
- these refer to BS and european standards
- most relevant to optometrist is BSE EN166 personal e ye protection-specifications
what are the two things that an optometrist must do after get qualified?
- Get professional indemnity insurance
2. Register with GOC (General Optical Council)
what is professional indemnity insurance?
- One must hold professional indemnity insurance cover valid for UK purposes in order to register with GOC
- one must not carry out any professional work outside the terms of the insurance policy
- The cover must be in place before the GOC accept the application for registration
How to get professional indemnity insurance?
- join a professional body that provides it
- Association of Optometrist (AOP)
- Federation of Opticians (FODO) - check if covered by employer
- note well that if take this insurance, one wont be covered for any other professional activity elsewhere (locum)
- most optometrist have their own AOP or FODO cover - Buy a policy on the open market
what are the core functions of the GOC?
SAMI
S- Setting standards for Education and Training, Performance and Conduct
A- approving qualifications for registrations
M- maintaining and publishing the registers
I- Investigating allegations that registrants’ fitness is impaired
What is General Ophthalmic Service (GOS)?
*with GPs, dentists and pharmacists,these are the non-NHS businesses that contract with the NHS to provide services to NHS patients, as well as offering services to private patients.
- the majority of optometrists and dispensing opticians work in local optical practices
- NHS optical services are called General Ophthalmic Service
—–> in wales, one can perform sight test under GOS only if on the Ophthalmic List or Supllementary Ophthalmic List of a health board in wales. (if want to work in england (must be listed in ophthalmic performer list of NHS england) and in wales, one must be listed seperately in both)
How to get and stay listed with the NHS?
- undergo ‘Disclosure and Barring’ check
- declare and keep NHS updated on fitness to practise- health, convictions, disciplinary matters (same as for GOC registration)
- provide evidence- qualifications, indemnity insurance, identification, professional experience, refrences, communication skills.
what are the functions of the AOP?
serves its members by…
1) promoting, protecting, representing, and supporting them
2) providing them with relevant services
3) enhancing their professional and business effectiveness
4) expanding the role of optometry
5) ‘like a trade union for optometrists’
- insurance
- defence
- advice
- education
- members’ interest