Optometry's Meeting® |  Optometry's Career Center® |  Ask a Question |  AOA News  
ALOA Home
About the ALOA| Doctors| Paraoptometrics| Students and Educators| Media
 
Clinical Care and Practice Advancement
Occupational Vision Manual Part I: Introduction

Occupational Vision Manual: Part III: Ocular Protection



by: Gregory L. Stephens, O.D., Ph.D.

Part I | 2 | 3 | 4 | 5 | 6

Occupational Safety and Health Administration (OSHA) regulations require that workers' eyes be properly protected from potential hazards in the workplace. It is important that optometrists be aware of the regulations covering eye safety and of the protective devices available to workers.

Types of Hazards and Appropriate Protection

The major hazards against which protection is needed in the workplace are projectiles, chemicals (splashes and fumes), and radiation (especially visible light, ultraviolet radiation [UV], and heat or infrared radiation [IR]). Methods of eye protection differ for each type of hazard, although an eye protector may provide more than one type of protection. The protector must be matched to the potential hazard. Laser eye protection recommendations are provided by the ANSI Z136.1-2000 and ANSI Z136.3-1996 standards. The ANSI Z87.1-1989 standard provides guidelines for selection of the appropriate eye or face protector for other types of hazard.

Projectiles. A projectile posing a hazard to the eye can be of almost any size or shape, and it can travel at either high or low velocity. Common projectiles in an industrial setting might include pieces of a screwdriver blade, drill bit, grinding wheel, metal debris, rock, and steel rod. They can cause injuries ranging from corneal or conjunctival foreign bodies, to penetration of the eye, to blunt trauma. Some projectiles (especially metals) can be toxic to the eye.

There are many ways to protect the eyes from projectiles, but the first line of defense is almost always industrial safety glasses. OSHA requires sideshields on the frames whenever there is potential for injury from flying objects, but they are not mandatory in all situations and need not be permanently attached. In practice, hazard assessments show that sideshields are required in many situations.

Any lens material that meets the impact resistance requirements of the ANSI Z87.1-1989 standard may be used in prescription industrial safety glasses. Polycarbonate is the material of choice because of its superior impact resistance, but there may be situations where its use is not indicated. For example, in cold weather a carpenter may have problems with sawdust sticking to polycarbonate lenses because of static electricity. Glass lenses may also be preferable to polycarbonate when scratching of the surface is likely to occur. At one time, workers who wanted photochromic lenses were restricted to glass or CR-39 plastic. The polycarbonate photochromic lenses are now available and are the preferred photochromic lenses for industrial eye protection.

Standard dress eyewear does not meet the ANSI Z87.1-1989 requirements for industrial eye protection. Frames and lenses for industrial use must meet specific requirements, including impact testing and minimum thickness requirements. In addition, lenses and frames must be labeled so that they can be easily identified as meeting the industrial standard. ("Z87" must be stamped on the frame, while the lens manufacturer's or optical lab's logo must be etched on the lenses.) Dress lenses should not be placed in industrial frames or industrial safety lenses in dress frames, because the resultant spectacles will not meet the requirements of the ANSI Z87.1-1989 standard in providing adequate protection from projectiles.

The numbers of industrial eye injuries that occur because proper industrial eye protection is not worn suggest the need to provide employees with industrial eyewear that has a pleasing cosmetic appearance and that fits comfortably. Plano spectacles are available in many different price ranges. Spectacles that are not easily adjustable or are easily broken or bent may not be the best option. Higher quality, more expensive plano eyewear may be more cost efficient in the long run because workers are more likely to wear a protector that has been individually adjusted for maximum comfort. Moreover, when workers experience "ownership" of the spectacles, they may be less likely to regard them as disposable (which can lead to high replacement costs).

Faceshields and goggles may be used to provide protection against projectiles. These types of protectors must meet specific requirements such as impact resistance and optical quality. The ANSI Z87.1-1989 standard provides guidelines for their selection and use. A faceshield, which usually consists of a curved sheet of plastic attached to a headband, provides protection for both the face and eyes. Faceshields are usually recommended for relatively severe exposure situations, such as working with a grinding wheel that rotates at high speeds. When used improperly, the grinding wheel can break apart, sending large, highvelocity projectiles toward the face and eyes. Faceshields must always be used with a so-called "primary protector," i.e. safety glasses or goggles. Goggles might be worn in an environment in which it is necessary to keep dust or chemicals from reaching the eye (e.g., sandblasting, woodworking, handling of chemicals or exposure to fumes). These devices conform to the face around the eyes, provide ventilation to the eyes, and accommodate a spectacle prescription.

Chemicals. The industrial environment often includes hazardous chemicals. In many cases, the major concern is injury caused by a liquid chemical that splashes into the eye; however, fumes, vapors, and dry chemicals can also be sources of eye injury. Chemicals that could cause injury include acids, alkalis, organic solvents, and surfactants. The NIOSH Pocket Guide to Chemical Hazards (1996) is an excellent source of hazard and safety information on specific chemical compounds. Included in the NIOSH recommendations are the levels of eye and skin protection needed and the placement of the eyewash stations and showers required for workstations at which the listed chemicals are used.

Protecting the eyes from chemicals requires more than just safety glasses. In most cases, the best solution is face-fitting goggles. Goggles are considered primary protectors, and safety glasses need not be worn under them. However, when a spectacle prescription is required, the prescription must be provided either in safety glasses that fit under the goggle or as prescription lenses in the goggles. Goggles are usually vented to prevent fogging. Chemical goggles have covers over the vents (indirect ventilation) to protect against splashed liquids. Fully sealing goggles, with no ventilation, are also available. Depending upon the potential for exposure, the worker may need a faceshield, respiratory protection, or skin protection.

The ANSI Z87.1-1989 standard does not address the issue of protection from exposure to blood or other body fluids (as encountered by a surgeon or dentist, for example). It is not a good idea to assume that a protector meeting the Z87.1-1989 standard will also provide proper protection against body fluids.

Radiation. The most common types of radiation encountered in industry are infrared radiation (IR) or heat, ultraviolet radiation (UV), and visible light.

Sources of IR in industry are primarily molten materials, specifically glass and metals. Many industries are automated, so that employees are not exposed to large amounts of IR, but activities such as glassblowing may produce significant exposures from low-level, long-term exposure (Oriowo et al., 1997). Epidemiological studies have demonstrated that long-term (chronic) exposure to IR in the glass and steel industries is associated with the development of cataracts (Pitts and Kleinstein, 1993). Relatively few of the available spectacle lens materials provide protection from infrared radiation. The best protector is a lens with a metallic coating (copper) that reflects IR (Pitts and Kleinstein, 1993).

Produced by both artificial sources and the sun, UV radiation is commonly encountered in industrial situations. Probably the most common industrial source is an electric welding arc, which emits large amounts of UV-C, UV-B, UV-A, visible light, and IR. Both the eyes and the skin must be protected from this radiation, as well as from sparks and molten droplets of metal produced during arc welding. The most common eye and face protector is a welding helmet. The helmet contains a multilayered faceplate (filter plate) that allows the worker to view the work. The faceplate must meet the specific impact resistance and radiation absorption requirements described in the ANSI Z87.1-1989 standard.

When a weld is finished, the welder must raise the helmet to view the work, at which point his or her eyes are vulnerable to injury from projectiles, debris, and radiation from other welders or other workers nearby. For this reason, a welder must also wear UV-absorbing safety glasses, of which polycarbonate lenses are usually the best. Welders' assistants and observers also require protection. Welding curtains can be used to surround the welding site and prevent inadvertent exposure. Tinted spectacle sun lenses do not provide adequate protection and should not be used for arc welding.

Gas welding and the processes of brazing, soldering, and cutting with torches also require protection from radiation. Protectors must meet the specific requirements specified in the Z87.1-1989 standard for both impact resistance and radiation protection (see Tables 1 and 2).

Many employees who work outdoors require sunglasses for comfortable vision in bright sunlight. Such employees are also exposed to UV radiation, which is a risk factor for the development of cataracts. A sunlens that absorbs both UV-B and UV-A radiation provides the best protection from UV radiation. Gray, brown, or green polycarbonate lenses provide excellent UV protection and have the additional advantage of providing protection from flying projectiles. The gray color is best when good color discrimination is important.

AOA guidelines for UV protection recommend that sunglasses provide at least 99 percent protection from solar UV radiation (UV-A and UV-B) at wavelengths below 400 nm. Gray, green, and brown polycarbonate prescription sunglass lenses will provide this level of protection. Gray, green, and brown CR-39 plastic sunglass lenses may require a UV-protective dye to reach 99 percent UV protection. Gray glass prescription sunglass lenses do not usually meet this recommendation.

The effects of visible radiation on the eye are of most concern for persons who are welding or using lasers. Although outdoor workers can be exposed to high levels of visible light, neutral gray sunglasses provide adequate protection.

Lasers have a wide variety of industrial and engineering applications, including welding, cutting and etching, photochemical processes, electronics design and manufacture, metrology, and surveying. Lasers are found in printers, compact disk players, and laser pointers, and they have become important medical and surgical tools. Laser output can be IR, visible, or UV radiation and power levels can easily be high enough to cause damage to the eye and skin.

Guidelines for laser safety and eye protection are provided in the ANSI Z136.1-2000 and ANSI Z136.3-1996 standards. All ANSI standards are classified as "voluntary," and OSHA has not adopted specific laser safety standards; however, OSHA often relies on published voluntary standards when evaluating industry hazards. The U.S. Food and Drug Administration (FDA ) has its own specific laser requirements that manufacturers must meet. Lasers are classified primarily by their ability to cause eye and skin damage, as summarized in Table 3.

Engineering and administrative controls are just as important as eye protectors in preventing damage to the eyes from laser beams. Controls include safety interlocks, barriers that block viewing of the beam, shutters, alarms, master switches, door interlocks, and warning signs. Using the proper control can usually prevent laser injury, even in the absence of eye protection.

The ANSI Z136.1-2000 standard recommends eye protection for the use of Class 3b lasers and requires eye protection for Class 4 lasers when engineering and administrative controls do not provide proper protection. Two general types of laser protection are available (Pitts and Chou, 1998). Wrap-around polycarbonate eyeguards are most commonly used to protect against Class 3 lasers. Enclosed monogoggles with replaceable filter plates are recommended for use with Class 4 lasers. The filter plates are designed to resist a laser beam long enough for the wearer to become aware of the problem and to move out of the path of the beam. Laser eyewear must have very high absorption of the laser wavelength for which protection is required, while allowing maximum transmittance of the visible spectrum. Specific labeling requirements are included in both the ANSI Z136.1-2000 standard and in government standards (OSHA, 1991). Protectors should be comfortable and should not be too dark, especially if the employee works in an area with low ambient light levels.

The laser safety officer (LSO) plays an important role in a laser safety program, especially when higher-power (Class 3 and Class 4) lasers are being used. The LSO’s duties, as described in the ANSI Z136.1-2000 standard, include providing employee training on laser safety, evaluation of laser hazards, and monitoring compliance with standards.

X-rays (ionizing radiation), microwaves, radio waves, and the electromagnetic fields produced by A-C circuits may also be encountered in industrial settings, but their effects on the eye and methods of protection are beyond the scope of this manual. For further information, see Pitts and Kleinstein (1993) and Chou and Pitts (1998).

Worksite Hazard Assessment

Since 1994 OSHA has required a job site hazard assessment for all workstations in an industrial setting. A hazard analysis begins with an on-site tour and an analysis of all work areas. First-hand information must be obtained about each work area. Input from foremen/supervisors and individual workers regarding potential eye hazards should be solicited. Company safety records should be reviewed to identify areas where past eye injuries may have occurred. The ANSI Z87.1-1989 standard recommends that special attention be paid to:

  • sources of motion that can create projectiles
  • employee movement patterns that could result in impact with stationary objects
  • sources of heat that could cause injury or exposure to IR
  • chemical exposures
  • sources of dust
  • sources of UV, visible or other radiation
  • the layout of the workplace
  • electrical hazards.

Light levels should be evaluated to determine whether lighting fulfills Illuminating Engineering Society (IES, 2000) recommendations for each task.

Laser hazard analysis may require some additional steps. Laser eye protection needs can often be determined by consulting with the laser manufacturer; however, when this information is not available, the LSO or other qualified personnel may need to calculate the maximum permissible exposures (MPEs) for each laser system to evaluate protection needs. The area around a laser can be hazardous, too, because of reflections or equipment failures, in which case it is necessary for the LSO to determine the nominal hazard zone (NHZ) for each laser system. The NHZ is the space surrounding a laser within which the level of direct, reflected, or scattered radiation exceeds the MPE. Instructions for calculating MPEs and performing an NHZ analysis are presented in the ANSI Z136.1-2000 standard. Finally, non-beam hazards associated with lasers must be evaluated. These include the risk of fire from the laser beam, electric shock from beam power supplies and electronics, exposure to hazardous laser gases and liquids, hazards from compressed gas cylinders, and exposure to fumes, vapors, and particles formed when a laser interacts with a target material.

Whenever possible, the best means of protecting workers' eyes is elimination or containment of the hazard at its source. For a non-laser hazard this might include modification of equipment or the work area, hazard shielding, regular maintenance, and the installation of exhaust systems that remove dust, gases, or fumes from the work area (Collins, 1983). Laser protection is best provided by engineering controls such as safety interlocks and beam shields.

In many cases, complete elimination of all eye hazards is not possible, and some form of personal eye protection is required. Once areas or work tasks have been determined as being hazardous to the eyes, a firm policy should be established regarding the use of protective eyewear:

  • all persons working in, passing through, or visiting these areas must wear adequate eye protection
  • appropriate warning signs should be conspicuously placed in all eye hazardous areas
  • supervisors need to be thoroughly familiar with the eye protection requirements within their areas and strictly enforce their use.

Employers must recognize the existence of eye hazards and provide employees with the necessary protective eyewear and safety training and ensure that employees comply with their use. Company management and a workers' committee should jointly develop specific disciplinary policies to be followed for workers who fail to comply. Some companies have made the use of safety eyewear a condition of employment.

Once a hazard analysis has been completed and proper protective devices have been selected, it will be necessary to re-evaluate the workplace at appropriate intervals. The occupational optometrist and plant safety officer should evaluate new equipment, review accident records, and assess the suitability of previously selected eye protection for a specific task.

Standards and Regulations for Protection Against Hazards

The primary standard pertaining to non-laser eye protection in industry is ANSI Z87.1-1989. This standard was prepared by members of the eyecare professions, industry and the military, among others, and covers all facets of non-laser eye safety and protection, including both prescription and non-prescription industrial safety glasses, face protectors or faceshields, welding hoods or helmets, and goggles. Transmittance requirements for the filters used for welding eye protection are also included. This standard is revised on an ongoing basis every 5 years, so it is important for the optometrist to be aware of the most recent version. Although the American National Standards Institute (ANSI) is a nongovernmental body, the U.S. Occupational Safety and Health Administration (OSHA), a governmental regulatory agency, requires that all industrial eye and face protectors meet the requirements of the ANSI Z87.1-1989 standard. OSHA may also specify additional requirements, such as the requirement for sideshields when there is a potential for injury from flying objects.

Laser eye protection recommendations are provided in two separate standards, ANSI Z136.1-2000 and ANSI Z136.3-1996.

Standards for industrial eyewear differ considerably from those for everyday, non-industrial (dress) prescription eyewear. Some of the most important differences include the impact resistance requirements and, for the industrial standard, specific requirements for the design and strength of the frame. Approval of dress eyewear requires only the FDA-regulated drop-ball test, while industrial eyewear must meet all requirements of the ANSI Z87.1-1989 standard.

Eye Emergency Procedures

Regardless of an eye safety program’s effectiveness, eye injuries will occur. In such an emergency, knowing what to do and how to do it may mean the difference between a minor eye injury and permanent eye damage. Everyone who works in an eye-hazardous area should be familiar with the general principles of first aid needed to deal with eye emergencies.

Occupational eye injuries may occur due to trauma or mechanical injury, from contact with chemicals or gases, or from exposure to radiation. Although injuries to the eyes may not be life-threatening, they can result in serious eye damage and disability. Quick, effective treatment can often mean the difference between a return to normal and permanent loss of vision. This is particularly true in the case of a chemical splash into the eyes. Immediate and constant flushing of the eyes and face is essential. This flushing action serves to dilute the chemicals and minimize their effect on eye tissue. Whenever chemical eye injury is possible, workers must have immediate access to appropriate eye wash stations.

Today's legal climate suggests the need for caution when examining a patient with a job-related eye injury. First, the most basic step in the evaluation of any eye injury is a good case history. Although obviously important for diagnostic and treatment purposes, a good history, along with comprehensive record keeping, can minimize the legal problems commonly encountered following occupational eye injury. Likewise, it is important that visual acuity be measured before any other procedure is performed.

TABLE 1
Transmittance Properties of Welding Filters

Shade
number
Luminous1 (%)
transmittance
Far UV
Ultraviolet
transmittance
(%)
Ultraviolet
transmittance
at 313 nm (%)
Ultraviolet
transmittance
at 365 nm (%)
Infrared
transmittance
(%)
1.5 62 0.1 0.0003 30 25
1.7 50 0.1 0.0003 22 20
2.0 37 0.1 0.0003 14 15
2.5 23 0.1 0.0003 6.4 12
3.0 14 0.07 0.0003 2.8 9.0
4.0 5.2 0.04 0.0003 0.95 5.0
5.0 1.9 0.02 0.0003 0.30 2.5
6.0 0.72 0.01 0.0003 0.10 1.5
7.0 0.27 0.007 0.0003 0.037 1.3
8.0 0.10 0.004 0.0003 0.013 1.0
9.0 0.037 0.002 0.0003 0.0045 0.8
10.0 0.014 0.001 0.0003 0.0016 0.6
11.0 0.005 0.0007 0.0003 0.0006 0.5
12.0 0.002 0.0004 0.0002 0.0002 0.5
13.0 0.0007 0.0002 0.000076 0.000076 0.4
14.0 0.00027 0.0001 0.000027 0.000027 0.3

Sources: ANSI Z87.1–1989, Table 1, and Canadian Standards Association (CSA) Z94.3–1999, Table 3.

  1. Luminous transmittance values are nominal values for the waveband 380–780 nm with reference to CIE Illuminant A and the CIE 1931 Standard Observer (ANSI Z87.1–1989). For specific limits, see also CSA Z94.3–1999.
  2. Recommendations for waveband 200–315 nm; average transmittance in the waveband 315–385 nm should be less than 1/10 of the luminous transmittance (ANSI Z87.1–1989).
  3. Transmittance for wavelengths 210–313 nm shall not exceed this level (CSA Z94.3–1999).
  4. For wavelengths 313–365 nm, transmittance shall not exceed this level; for wavelengths 365–400 nm, mean spectral transmittance shall not exceed luminous transmittance (CSA Z94.3–1999).
  5. Recommendation for waveband 780–2000 nm (ANSI Z87.1-1989). Maximum mean transmittance values for wavebands 700–1300 nm and 1300–2000 nm (CSA Z94.3-1999).

TABLE 2
Recommended Shade Numbers for Welding Operations

Operation Shade Recommended Protector
Torch soldering 1.5-3 Spectacles or welding faceplate
Torch brazing 3-4 Welding goggles or faceshield
Cutting 3-6 Welding goggles or faceshield
Gas welding 4-8 Welding goggles or faceshield
Gas tungsten arc welding 8-10 Welding helmet or shield
Gas metal arc welding 7-11 Welding helmet or shield
Flux core arc welding 7-11 Welding helmet or shield
Plasma arc welding 6-11 Welding helmet or shield
Electric arc welding 10-14 Welding helmet or shield

Although recommended shade numbers prevent radiation-induced ocular injury (ANSI Z87.1-1989), Sliney and Wolbarsht (1980) have noted that filters with higher shade numbers may be needed to ensure visual comfort throughout a full working day of exposure to a welding arc.

TABLE 3
Summary of the ANSI Z136.1-2000 Laser Hazard Classification

Laser class General Description
1 Incapable of producing damaging radiation levels during operation and maintenance. No eye or skin hazard from full-day exposure.
2 "Low-power" laser. Emits in visible portion of the spectrum. No eye hazard from intrabeam exposure within aversion reflex time.
3 "Medium-power" laser. Eye hazard from intrabeam exposure and from specular reflection within aversion reflex time. Diffuse reflections do not usually present a hazard (unless laser beam is focused or of small diameter and viewed from a short distance).
4 "High-power" laser. Eye and beam hazard from intrabeam viewing or diffuse reflection. Fire hazard if combustible materials are exposed to beam. May also produce air contaminants and hazardous plasma radiation.