‘Head down, straight on!’ is seldom good advice.
In the case of certain actvities your eyes need special and considerably more protection than your own eyelids can possibly offer. There is a whole series of protective products for people working in professions where there is a particular risk to their eyes and face. Such products prevent acute and lasting damage.
Anatomy of the eye
The eye is one of the organs through which some living organisms (human included) visually perceive their environment.
The human eye is a very complex and delicate structure. The human eye is made up of the following:
- The Cornea The cornea is the clear transparent part in front of the eye, through which light passes to the lens
- The Pupil The pupil is the opening or aperture of the iris
- The Iris The iris controls the amount of light that enters the eye. It achieves this by enlarging the aperture (pupil) in dim light and contracting in bright light
- The Retina The retina comprises of light-sensitive endings that carry the visual impulses to the optic nerve. It is found at the back of the eye
- The Optic Nerve The optic nerve conducts visual impulses from the brain which acts as a computer
- The Lens The lens as the name suggests, helps to focus light to the retina o The Sclera The sclera forms the white of the eye
- The Vitreous The vitreous is a transparent colourless mass of soft gelatinous material filling the eye ball behind the lens
How the eye works
The eye works by focusing light from objects onto the area at the back of the eye called the retina. Light energy enters the eye through the cornea. The lens bends (refracts) the light until a majority of the light energy is focused on the retina. Since the retina is sensitive to light and can be damaged by excessive light energy, the iris regulates the amount of light entering the eye by adjusting the size of the pupil. The pupil gets smaller with the increase in light falling on the eye.
The retina consists of light sensitive cells called rods and cones. The rods are concentrated on the edge of the retina and are mainly for peripheral vision and detection of moving objects. The cones are in the centre of the retina and are responsible for detailed vision and colour vision.
The optic nerve sends the signals from the eye to the brain, the retina captures the image and the brain interprets the image.
The most common type of eye injury is from flying objects. Work that results in the generation of a substantial amount of particles, fragments, sparks or dust is likely to cause eye injuries, if adequate protective measures are not implemented. Other sources of eye injuries are hazardous substances or radiation energy.
Types of eye protective devices
Safety glasses Safety glasses provide minimum protection often against flying particles or dust. Safety glasses are designed with side shields.
Goggles Goggles provide more protection than safety glasses. Care must be taken to ensure that goggles do not fog. Goggles do not provide splash protection to other parts of the face. Prescription safety goggles are safety glasses with prescription lenses. Such types of glasses usually have side shields.
Face shields Face Shields are used when there is a need to protect the eye as well as the rest of the face, protection might be against high impact hazardous substances or blood borne hazards. Face shields are always worn as secondary protection. Safety glasses or goggles are worn under face shields.
Full face respirators Full face respirators are primarily for respiratory protection but because of their design also, offer protection for the face and eyes. Full face respirators are usually used where there is a hazard of infection.
Special mention should be made of the hazard due to different types of radiation. The most common form of radiation in the workplace is radiation from welding and ultra violet radiation. Protection is through use of shaded protective eyewear.
European Council Directives
Protective eye equipment falls under the classification of personal protective equipment (PPE) for the purpose of the European Council (EC) Directives.
The placing on the market of PPE is governed by the EC Directive 89/686/EEC.
The rationale of governing the placing on the market of PPE by an EC Directive is multi-purpose. Some of the reasons for controlling the marketing of PPE through an EC Directive are:
- Removal of trade barriers
- Unification of the various national requirements in forms of application and use of PPE
It should be noted that the Directive is not prescriptive. It only defines the basic requirements to be satisfied by personal protective equipment. Proof that PPE conforms to the basic requirements of the directive is by ensuring that the PPE is designed, manufactured and tested to the relevant harmonised European Standards. Attestation of compliance to conformity to all the provisions of the Directive is through CE marking. In some cases, compliance to the directive requires the involvement of a notified body.
EC Type Examination
Approved inspections bodies establish and certify that the PPE model in question satisfy the relevant provisions of the Directive.
Undertaking of the EC-Type examination entails inter-alia; the examination of the manufacturer’s technical file and the examination of the model.
The purpose of the examination of the manufacturers technical file is to establish compliance to all the relevant harmonised standards. The authorised inspection body verifies that the model has been produced in accordance with the manufacturer’s technical file and undertakes the necessary tests to establish the conformity of the model with harmonised standards.
It is important that the manufacturer of PPE ensures the quality of the end product as part of the quality assurance programme, a notified body undertakes random audits.
It is also mandatory that a manufacturer or his authorised representative established within the community, draws up a declaration of conformity certifying conformity of the PPE to the provisions of the directive. The manufacturer is also obliged to display the CE mark on the PPE.
When placing PPE on the market, the manufacturer must label it with the following information
- Name and address of manufacturer and/or his authorised representative in the community
- Information on storage, use, cleaning, and maintenance
- Results of tests undertaken indicating levels of offered protection
- Appropriate accessories
- Validity period of the equipment
- Significance of the markings
- The name address and identification number of the notified body involved in the design stage of the PPE
In the designing of PPE for the face and eyes, the following must be taken into account;
- The equipment must be designed such that any restriction of the users field of vision or sight is minimised
- The equipment must be designed to minimise moisture formation
- If applicable, the PPE must be compatible with the wearing of spectacles or contact lenses
Eye protective devices are used to prevent eye damage from radiation. Such protective devices must be capable of reflecting or absorbing most of the harmful radiation while transmitting the harmless part of the visible spectrum. The effects of radiation must not adversely affect the protective glasses. The appropriate protection-factor number must be marked on all specimens of filtering glasses by the manufacturers.
Eye protection is also worn to protect the surface of the eye from contact with dangerous substances and infective agents. Such protective glasses must be capable of preventing the penetration or diffusion of harmful substances.
Farayi A ManyikaProject EngineerTÜV International UK24 Bennetts HillBirminghamB2 5QPUnited Kingdom
Tel: +44 (0)121 634 8000 www.uk.tuv.com
For more information on Protective Eyewear please visit http://www.osedirectory.com/product.php?type=health&product_id=9
Published: 10th Apr 2006 in Health and Safety International