Continuing Education

Gordon Carson looks at the legislation governing the use and supply of protective eyewear and offers useful advice about identification and interpretation of the markings. (C3474, one standard point)

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Optometrists and opticians are regularly required to dispense appliances which offer protection in a variety of work or leisure situations. They also need to ensure that the appliance worn by any patient is suitable for the tasks undertaken. It is also reasonable to expect the practitioner to be able to look at an appliance and understand the markings so that any decision of suitability may be made.

This article will briefly look at the various legislation and standards surrounding safety eyewear, and then give a more detailed description of markings and their interpretation.

Responsibility

The are two pieces of legislation that control the provision of eye protection:

• Health and Safety at Work Act 1974 - this defines the responsibility of an employer and an employee to ensure a safe working environment
• Personal Protective Equipment at Work Regulations 1992 - this includes sections on the provision, maintenance, and compatibility of 'personal protective equipment'.

With specific regard to protective eyewear, it is important to understand the responsibility of three parties - the employer, the optometrist, and the employee.

Much of the onus of responsibility lies with the employer. As laid out in the Health and Safety at Work Act, there is a general duty for employers to 'ensure so far as is reasonably practicable the health, safety and welfare of all their employees'. The employer needs to establish whether there is any task requiring eye protection, and also whether the employee requires training in the use, the fitting and the storage of any protective appliance.

Hazards are defined by the Health and Safety Executive PPE Regulations (1992). The employer is legally responsible for assessing the categories of risk to which that the worker will be exposed. This appropriately titled 'risk assessment' may be carried out by a dedicated health and safety officer in larger companies, or a named staff member in smaller concerns. A risk assessment will address all the possible hazards to the eyes, or indeed to other parts of the body.

Eye protection may be required when there may be a risk from any or all of the following:

• Impact
• Optical radiation
• Molten metal/hot solids
• Liquid droplets/splashes
• Dust
• Gases.

The risk assessment then allows the appropriate and relevant appliance to be ordered.

The optometrist's responsibility is in three parts and relates to the appliance supplied. A practitioner needs simply to ask three questions about any appliance being supplied:

• Will this appliance provide appropriate protection for the task?

For example, protection from a gas hazard will only be provided by goggles. Supplying spectacles in this instance would not be appropriate as the gas would leak through the side shields.

• Will this appliance be comfortable?

Protective eyewear is not usually worn in isolation. They are often combined with ear defenders, respirators, faceshields and hard hats

• Will this appliance be fit for the job?

Protective eyewear is subject to rough treatment. Be especially aware where there are additional hazards such as organic solvents. This would, for instance, exclude polycarbonate as a material for oculars.

If in doubt, the practitioner needs to refer to the health and safety officer or ask the patient to bring in all their personal protective equipment to make sure that it all fits together happily.

The employee's responsibility is simple, assuming full compliance is achieved. Remember that 70 per cent of accidents which are dealt with by hospital services are due to industrial processes. This suggests employees do not usually wear eye protection until they have been injured. The employee is required to use the appliance and report loss or any defects.

Relevant Standards
There are a whole host of standards which apply to protective eyewear and these are listed in Table 1. It is worth pointing out a few specific details.

BS EN 166 (2002) - Personal Eye Protection Specifications - lists the regulations for eye protection and covers spectacles, goggles, and faceshields. It also includes specifications for welding, ultraviolet, infrared and sunglare filters. The markings on the lenses (oculars) and frames (housings) of all protective eyewear are written in code, something many readers will remember learning for their PQE examinations.

The sequence and content of the markings is different for the oculars and housing and will be discussed in some detail later in this article.

There are two additional standards to describe the optical (BS EN 167: 2002 Personal Eye Protection - Optical test methods) and non-optical (BS EN 168: 2002 Personal Eye Protection - Non- optical test methods) tests for protective eyewear. Appliances are tested to ensure they conform to the standards.

Table 2 gives a complete list of tests that appliances may undergo. The non-optical tests are designed to ascertain the performance of the eye protector under normal and hazardous circumstances. The principal area of interest to the optometrist will be resistance to high-speed particles.
Not all these non-optical tests will apply to protective spectacles - some may only relate to goggles or face shields.

Markings at a glance
The symbols on the oculars (lenses) are listed in Table 3. These come in a specific order and are more complex than the markings used under the now obsolete BS 2092.

There will be incorrect use of the appliance if the symbols are not interpreted correctly. There are further markings used on the housing (or frame) and these are listed in Table 4. These come in a specific order and if the symbols are not interpreted correctly there will be incorrect use of the appliance.

Scale numbers and filters
Scale numbers relate to filter lenses only. A scale number is a shorthand way of describing the attenuation of any filter in visible, infra-red and ultraviolet wavelengths.

All filters have a scale number, but some filters have a prefix before the scale number. For example, the eye protector in Figure 1 provides protection from ultraviolet radiation as well as impact. The filtration properties are shown by the prefix 2 and scale number 1.2. This is written as 2 - 1.2. Welding filters are the exception and will only have a scale number which will be in the range of 1.2 to 16. A welding filter with a shade number of 14 would simply be written as 14.

The full list of prefixes used for filter lenses are listed in Table 5.

Manufacturer's ID

This is a symbol or trademark that varies depending upon the manufacturer.

Optical class

The tolerances applied to the lenses are described as optical class. The optical tests are for spherical, astigmatic and prismatic power; light diffusion; assessment of quality of material and surface and transmittance. The test methods are mainly of interest to the manufacturer (but can be found in BS EN 167). The tolerances are summarised in Table 6.

Mechanical strength
The tests for mechanical strength of an appliance (impact resistance) now have to satisfy on four levels:

• Increased robustness
• Low energy impact
• Medium energy impact
• High energy impact.

The term 'minimum robustness' relates only to cover plates (used in welding) and oculars with a filtering effect if these are not intended to be impact resistant.

Increased robustness
Increased robustness is the lowest grade of impact resistance. This is assessed with both the complete appliance and an unmounted ocular. The non-optical test uses steel balls of different size, mass and velocity. The appliance must withstand the impact to exacting guidelines (Table 7). The tests must be conducted against forward and lateral projectiles. Having passed this test, the ocular will be marked with a letter S.

Low, medium and high energy impact resistance
To satisfy the criteria for low, medium or high impact resistance, the appliance and ocular must surpass the tests for increased robustness. Then, the appliance will be subjected to impact testing appropriate to the mechanical strength (Table 8). If the velocity of the steel ball is converted to miles per hour, the high energy impact appliance will withstand an equivalent of greater than 420mph.

Non-adherence of molten metals/penetration of hot solids
If resistant, the appliance will be marked with a number 9.

Resistance to surface damage by fine particles
If resistant, the appliance will be marked with a letter K.

Resistance to fogging
If resistant, the appliance will be marked with a letter N.

Enhanced infra-red reflectance
Oculars will carry an additional letter R.

Protection of high speed particles at extremes of temperature
The specification requires that the ocular must retain impact resistance over a range of temperatures (-5C to +55C 2C).This will be marked on the ocular with a letter T and is combined with the impact resistance. For example, BT on the ocular would indicate medium energy impact resistance (120ms-1) over a temperature range of -5 to +55C.

Original or replacement oculars
Some appliances can have their oculars replaced. The standards now allow the manufacturer to mark the oculars as original or replacement, original as O and replacements as <2207>. This is an optional marking.

Laminated oculars
Orientation is significant with laminated oculars. The specification allows the lenses to be marked at the nasal edge to ensure that, if replaced, they are put into the housing the correct way round. The design of the marking is not specified.

Certification mark
There may be a certification mark which, in the UK, is a kite mark. In Europe the mark may be a DIN number, and in the US manufacturers will usually carry an ANSI number.

The kite mark is a system of quality control operated by the British Standards Institute. Use of this mark on a product is an assurance that the eye protector has been produced to comply with the standards of the BSI and is subject to inspection by that body. The manufacturer has to submit their production for periodic inspection. There must also be a CE mark on protective eyewear which confirms that the product complies with medical devices regulations.


Housing Markings in detail


Manufacturer's ID
This is a symbol or trademark that varies depending upon the manufacturer.

Standard
BS EN 166 will appear only on the housing. The mark should not appear on the oculars or filters.

Field of intended use
The appliance will only be approved for use in certain circumstances. In plain terms, what will the protection be used for? In some cases, there may be two fields of intended use. For example, the goggles shown in Figure 3 may offer protection from liquids and dust particles. The fields are summarised in Table 9.

Resistance to high-speed particles
The housing will be marked in the same letters as the ocular, except there will be a hyphen prefix as shown in Table 10. The impact resistance of the ocular and housing should be identical. Differences suggest that parts may have been replaced. If the markings for the oculars and the housing differ, the appliance will adopt the lowest level of impact resistance. It is important and easy for eye care practitioners to check this.

Mechanical strength at extremes of temperature
The markings should match those on the ocular, for example, BTmeans medium energy impact resistance over a range of temperatures between -5 and +55C.

Designed to fit a small head
The housing will carry a letter H.

Highest ocular scale number
(compatible with the housing)
Not all housing are suitable for extremely high levels of protection from radiation. The radiation (of whatever kind) may 'leak' around the sides of protective spectacles but would not 'leak' around a box goggle. There will be a shade number printed on the housing, for example, 2.5.

Certification mark
The same applies as with the ocular markings (see earlier).

Ocular/lens materials
There are several types of materials available for protective eyewear as follows:

• Glass - heat or chemically toughened (latter not readily available in the UK)
• PMMA - not widely used and largely replaced by CR39
• Polycarbonate - this is widely used in spectacles, goggles and faceshields. It scratches easily and has a low v-value which may lead to chromatic aberration. It is important to remember that hardcoating weakens the lens, and that polycarbonate is not resistant to solvents such as acetone
• Trivex - this is a new-generation material, comparable to polycarbonate, with enhanced resistance to solvents. Improved chromatic aberration versus polycarbonate
• Cellulose acetate - used in goggles, faceshields and plano one-piece eye protectors
• Laminated - a sandwich of glass and resin, now less commonly used for eye protection.

Housing/Frame Materials

Spectacles are made from cellulose acetate, metal (nickel silver/stainless steel) or polyamide (nylon). The practitioner should note that metal frames may cause more damage if subject to impact as the rim screws may work loose, lenses may come out and the frame or nose pads may cut the face.

In addition, metal frames are not suitable for use in either a hot environment (due to heat conduction) or where there is the risk of electrocution (due to electrical conduction).

Plano eyewear (injection moulded) is made from polycarbonate or perspex. Goggles and faceshields are made from polyamide or polyvinyl chloride.


Summary

Everyone involved in the provision of protective eyewear needs to be aware of their responsibilities. Importantly, eye care practitioners should understand how appliances are marked and the relevance of such markings so that they may identify where an appliance is not necessarily suited to a particular task.

Background reading
D Elks. The Specification of Safety Eyewear. Optometry In Practice Vol 5, 2004; 33-40.
Carson G. Practice-based dispensing Part 4 - Protective eyewear in practice. Optician, 2001; May 18, No 5801, Vol 221.
North R Eye Protection and ocular hazards - standards and requirements. Optometry Today, 2003; November 14 2003.
Williams K. Toughen up your patients - Get into protective eyewear. Optometry Today, 2003; September 5.
Carson G. Protective Eyewear. Optometry In Practice Vol 1, 2000; 27-36.

Web references
British Standards Online
Health and Safety Executive
Occupational Optometry DOCET

• Gordon Carson is clinical development manager for Dollond & Aitchison and chairman of approvers for the GOC CET scheme administered by Vantage

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