Contact Lenses and Work.pptx

Contact Lenses and Work for occupational optometry

1. Contact Lenses and Work

2. What are contact lenses? Contact lenses are small, thin discs made of a transparent material. The outer surfaces are custom-shaped to correct or improve vision and the inner side is carefully formed to fit the surface of the cornea (the clear, front covering of the eye including the iris and pupil). Today, the lenses are typically soft (flexible) but hard (rigid) are still available.

3. What is the controversy about wearing contact lenses at work? Dusts or chemicals can be trapped behind the lens and cause irritation or damage to the cornea or both. Gases and vapours can cause irritation and excessive eye watering. Chemical splash may be more injurious when contact lenses are worn. This increased risk is related to the removal of the lenses. If removal is delayed, first aid treatment may not be as effective and, in turn, the eye's exposure time to the chemical may be increased.

4. The critical point to remember is that contact lenses are not intended to be used as protective devices They are not a substitute for personal protective equipment (PPE) If eye and face protection is required for certain work operations then all workers, including contact lens wearers, should wear the proper protective devices. Safe work conditions for all workers are only possible when basic occupational health and safety practices and procedures are followed.

5. Are there situations where it may be hazardous to wear contact lenses? Soft lenses are made from a type of plastic that contains a large proportion of water. The soft lense adheres more tightly to the cornea and does not have as much fluid motion as the hard contact lens. For these reasons, some researchers think the soft lens offers some, but not total, protection against entrapment of foreign substances between the contact lens and the cornea.

6. The major risks for soft contact lens wearers are from chemical splashes and from hot, dry environments. Because of the high water content of the soft contact lens, some chemicals can pass through the lens and be held against the cornea by the lens itself. Hot, dry environments can lead to problems because they can cause the tear layer (upon which the lens 'sits') to dehydrate. This situation results in eye discomfort.

7. What are some other possible concerns when wearing contact lenses? The concern about the use of contact lenses with respirators or personal protective hoods arose because it was believed that dislodgement or sudden loss of a contact lens while wearing a respirator could lead to two potential problems. First, it is impossible to adjust or replace a contact lens while wearing such equipment in a hazardous environment. Secondly, the dislodged contact lens could become trapped in a part of the equipment that prevents its proper functioning.

8. Can you wear contact lenses when welding? The CSA(CANADIAN STD ASSOCIATION) Standard W117.2-12 states that contact lenses should not be worn by welders and welding personnel because foreign bodies in the eye can cause excessive irritation. Contact lenses do not provide protection from ultraviolet radiation and flying objects. Welders must wear appropriate eye protection according to the circumstances.

9. Reports of contact lenses being "welded" to the cornea (or lens of the eye) as a result of exposure to an arc flash have been proven to be incorrect. It is impossible for contact lenses to become "welded" to the cornea. Note that in Canada, Prince Edward Island's Occupational Health and Safety Act Regulations (E.C. 180/87) Section 45.11 specifically bans wearing contact lenses while welding.

10. Your Role… To determine whether contact lenses are advisable in a specific environment, consider the effect of the various risk factors both on the eye and in the individual who is not wearing contact lenses.   Once you determine this, you can evaluate the risk using the known physical parameters and physiological effects of the contact lens.

11. There may or may not be laboratory studies, epidemiological data or well documented case reports to support or refute your theoretical conclusions. An extensively referenced review of contact lens use in a large range of environments is available Some particular factors to consider: any toxic physical or chemical agent, any mechanical hazards, raw materials and byproducts, potential for exposure, protective equipment (provided/available/ worn) and other protective measures. Also, consider hygiene facilities, health personnel on staff and factors that affect compliance.

12. Additional Risks Barometric pressure . Extremes of barometric pressure occur at high altitudes and under water. Bubble formation occurs in haptic lenses at altitudes greater than 5,400m (more than 17,000 feet). Corneal thickening response with soft lenses increases with altitude. Bubbles may also form under gas permeable and soft lenses during decompression from hyperbaric exposure.   Even so, contact lenses have been safely used for various high altitude and underwater activities. One precaution: A potential microbial hazard from Pseudomonas aeruginosa has been reported in pressure chambers.

13. Vibration stress.   This may be encountered while operating machinery, such as pneumatic drills or chain saws, or while travelling in or on modes of transportation ranging from low-capacity motorcycles to aerospace vehicles. Visual acuity is impaired at vibration between 6 and 8Hz. This effect occurs with spectacles, contact lenses and the naked eye. Soft lenses are not dislodged regardless of vibration level.

14. Acceleration stress . We might expect high G forces to cause a contact lens to dislodge from the cornea. However, contact lenses are not displaced by more than a few millimeters under high acceleration forces. Indeed, combat pilots have worn contact lenses when exposed to forces up to +12G. Zero gravity of space flight has little negative effect on the cornea-contact lens relationship

15. Humidity.  The optimum range for comfort is 40% to 60%. Ambient temperature and humidity have not been found to be important factors for contact lens wearers, except for those wearing very thin high-water-content lenses. Wear of such lenses in very dry condition (i.e., low humidity) can result in slight corneal desiccation or aggravation of an existing dry eye conditions.

16. Wind.  Wind can be expected to have two effects in the eye: drying and stimulation of tearing. So, whether an individual worker in these and similar occupations can safely and comfortably wear contact lenses can only be evaluated by trial.

17. Computers . The computer user who wears contact lenses has fewer surface reflections and perhaps fewer aberrations than spectacle lens wearers. These advantages are offset by several potential disadvantages. Myopic wearers require a presbyopic addition earlier. Low levels of astigmatism may contribute to video display terminal (VDT) user discomfort. Also, computer tasks requiring concentration may reduce the blink rate, which in turn reduces lens movement and increases drying effects.

18. Commercial office buildings . In offices in which poor air quality contributes to so-called sick building syndrome, we can anticipate that factors such as temperature, relative humidity, air movement, CO2 levels, and airborne pollutants could adversely affect contact lens wear in a variety of ways.

19. Military.  Some occupations do not allow an individual to adhere to wearing schedules or lens care protocols. There may also be a lack of hygiene facilities and an increased level of chemical, mechanical, physical, microbial and biological hazards. This became apparent to the U.S. military during various deployments since the 1990s.

20. Recent events and reports have revealed non-compliance with USCENTCOM FHP (United States Central Command Force Health Protection) policy. According to USCENTCOM, due to the risks associated the lack of adequate hygiene, dust and dirt, of the deployed environment, lens wearers have experienced documented eye infection, damage, and loss of combat capability

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