Illumination is a work place hazard that is often overlooked and is influenced by so many other non-workplace exposures that it is difficult to pin point the actual culprit when it comes to making a diagnosis on eye disease. The reason being, that it is difficult to quantify the difference between workplace light exposure and non-workplace light exposure.
Light is defined as the visible part of the electromagnetic radiation within a range of 380-780 nm. In humans (as in the case of all mammals), light acts directly on the retina of the eye to fulfil both visual function and non-image forming tasks. Visual function There are two types of photoreceptors in the human retina called rods and cones. Rods are responsible for scotopic (low light level) vision and do not medicate colour vision and have a low spatial acuity. Cones are responsible for photopic (higher light level) vision and are capable of colour vision and responsible for high spatial acuity. Non-image forming tasks Non-image forming tasks include: synchronisation of the circadian rhythms to a 24-hour solar cycle; pineal melatonin suppression; and pupil light reflexes.
Very bright light, like staring into the sun – even if just for a short period of time – can cause permanent damage to the retina. On the other hand, if the light is not so bright, permanent retinal damage may occur from chronic exposure. Chronic exposure is caused by what is called Photo-oxidative damage, when the light reacts with the retina producing reactive molecules that cause damage to the surrounding molecules. Blue light exposure increases the risk of agerelated macular degeneration (AMD). Blue light has a short wavelength with a range of 460-500 nm. Artificial light sources emit more blue light than natural solar light.
Modern society has increased its exposure to artificial illumination, causing changes in both the light/dark cycle and light wavelengths and intensities. This artificial illumination is also referred to as light pollution and may have a strong impact on people’s health, as it may produce retinal degeneration because of photoreceptor or retinal pigment epithelium cell death. Light pollution can be found all over in private homes, the work environment, the social environment – even the streets are illuminated at night. Urban development leads to an increased use of baby lights, televisions, computers, light produced by mobile phones and tablets, light bulbs, etc. and is constantly growing daily as the population demand increases.
Environmental brightness plays a major role in the synchronisation of human circadian rhythms to solar light-dark cycles. Interference with the environmental light-dark cycle can cause abnormal circadian rhythms and may result in dysfunctionality in the human psychological and physiological mechanisms. Excessive night time illumination could interrupt the normal sleep patterns of a person, thus decreasing total sleep time and sleep efficiency with an increase in REM sleep. REM sleep refers to that portion of sleep when there is rapid eye movement (REM); a person typically has three to five periods of REM sleep per night. Too much REM sleep can leave a person feeling tired the next day.
Ocular fatigue results from intolerance of the human eyes to excess light exposure and is even more aggravated by blue light. Ocular fatigue, also known as eye strain, manifests as a combination of eye discomfort and visual impairment. Tired eyes, blurry eyes, itchy eyes, burning eyes or increase in teary eyes are all symptoms of ocular fatigue. Continuous exposure to relatively low ambient luminance of 5-10 lux during sleep, significantly increased ocular fatigue in the morning.
Exposure to sunlight can cause inflammation of the eyes as a result of UV ray exposure and is called photokeratitis. Arc welding, as well as reflections from the sun on concrete, water, sand or snow can also cause photokeratitis. UV ray exposure to the cornea of the eye causes photokeratitis.
However, should the UV rays affect the retina of the eye, the risk is greater of getting permanent visual deficits. One should also keep in mind that indoor halogen and fluorescent lightbulbs emit ultraviolet light to a certain extent.
Cumulative UV radiation due to sunlight exposure can cause damage to the eyes and eyesight over time. UV radiation is invisible to the human eye and is composed of three main wavelengths: UVA, UVB and UVC. UVB rays are absorbed by the cornea and cannot reach the retina, but UVA radiation passes through the cornea to the lens and retina. As discussed above, the short-term exposure to high doses of UV radiation can cause photokeratitis, but it can also lead to a condition known as photoconjunctivitis.
The long-term effects of sunlight exposure to the eyes are the possibility of developing cataracts, pterygium, pingueculae, squamous cell cancer of the conjunctiva, skin cancer of the areas surrounding the eyes and even macular degeneration. Each of these conditions are discussed in short below.
Although cataracts are related to ageing, one of the causes is UV ray exposure over time. As one ages and the lens of the eye grows older, the cells of the lens die and accumulate over time, turning the lens yellowed and cloudy. Cataracts can be treated surgically.
Pterygium is a soft fleshy overgrowth of the conjunctiva that starts in the medial corner of the eye near the nose. It is usually painless, but if it grows across the cornea it causes visual impairment. Should visual impairment occur, it should be surgically removed.
Pingueculae is like pterygium, as above, but it will not grow across the cornea.
Squamous cell cancer of the conjunctiva
Squamous cell cancer appears as a nodule on the front of the eye and there may be visible blood vessels leading to the nodule. It is a slow growing tumour that may result in loss of sight. Advancedstage squamous cell cancer of the conjunctiva can be treated surgically, and an extensive surgical approach is sometimes inevitable. Early detection is core.
Skin cancers around the eyes, especially on the eyelids are common in sunny countries with high UV exposure indexes. Any spots, moles or other lesions around the eyes should always be examined by a doctor or dermatologist. Some lesions can be benign, and others may be malignant or cancerous, therefore it is important to seek medical advice should growths on the eyelids or around the eyes be detected.
“artificial blue light can increase certain types of cancers”
As long-term UVA is responsible for most of the damage to the macula, one should seek medical attention as soon as blurred vision or no vision at all occurs in the centre vision field of the eye(s). The disease rarely affects the peripheral or side vision. As with cataracts, macular degeneration is an age-related condition, but can be exacerbated by exposure to UV rays. Macular degeneration cannot be reversed; however, progression can be slowed by therapeutic approaches.
As one can see from the aforementioned medical eye conditions (that can be caused by UV ray exposures), employers should issue employees working in the sun (or where there is a possibility of UV ray exposure) with eye wear that protect the employees’ eyes from such exposure.
Blue light is everywhere. The sun, television sets, computers, laptops, smart phones and tablets, fluorescent and LED lighting are all sources of blue light. However, one needs to distinguish between natural blue light and artificial blue light. When the light from the sun travels through the atmosphere, the shorter, high energy blue wavelengths collide with the air molecules causing the blue light to scatter everywhere, resulting in the air looking “blue”. The body’s circadian rhythms use this natural form of blue light to regulate the natural sleep and wake cycles. Natural blue light therefore comes from the sun and helps boost alertness, heighten reaction times and increases the overall feeling of wellbeing. Artificial light sources are humanly created devices like cell phones, laptop computers, energy efficient fluorescent bulbs and LED lights.
As explained above, blue light is shorter in wavelength, in fact, it is among the shortest, highest energy wavelengths in the visible light spectrum. Blue light, also called High Energy Visible (HEV) wavelengths flicker more easily than longer, weaker wavelengths; creating a glare that can reduce visual contrast and affect sharpness and clarity. This results in the eyestrain, headaches, and physical and mental fatigue that is caused by sitting in front of computer screens or other electronic devices for extended periods of time. The human eye does not provide enough protection against blue light, be it natural or artificial. Prolonged exposure to blue light may cause retinal damage and macular degeneration that can lead to vision loss.
The beneficial effects of natural blue light can be summarised as follows:
- It helps regulate the circadian rhythm of the body
- It boosts alertness
- It helps with increased memory and cognitive function
- It can elevate the mood of a person
Some of the harmful effects of artificial blue light can be summarised as follows:
- It disrupts circadian rhythms and can keep a person awake at night if exposed to blue light before bedtime
- It can lead to digital eyestrain syndrome: blurry vision, dry and irritated eyes, headaches, neck and back pain and difficulty focusing may be some of the symptoms
- It can increase certain types of cancers
Both natural and artificial blue light may cause permanent eye damage and may contribute to age-related macular degeneration.
Hazards that need to be assessed must include:
- UV rays
- Bright light
- Blue light
- Insufficient light
- Improper contrast:
- Identify areas with great differences in light levels
- Identify objects that are hard to distinguish from the background
- Identify reading material where it is hard to make out the print or characters from the background
- Poorly distributed light:
- Identify dark areas or areas of uneven lighting
- Shadows on the work surface and stairways
- Improper fixture placement based on the luminaire’s spacing criteria
- Workers complaining of eye strain after a day’s work
- Visual discomfort when tasks require frequent shifting of view from underlit to higher illuminated areas
- Stroboscopic effect of lighting on rotating machinery
- General cleanliness of luminaires and lamps
- Emergency evacuation routes conforms to minimum lux of not less than 0.3 at floor level and are capable of being activated within 15 seconds of electricity failure. It should also be capable to last long enough to ensure safe evacuation of all indoor workers.
“insufficient light may pose a safety hazard but can also affect the quality of work, especially if precision work is required”
Protecting the eyes from damage caused by lighting
When working in the sun or other places where UV ray exposure may be possible, a person should wear sunglasses and a hat to protect them from possible retinal damage. SPF should be applied to the eyelid areas when constantly working in the sun, as this sensitive area around the skin is where ten percent of skin cancers occur.
As blue light can also cause retinal damage, ophthalmologists can now offer blue-blocking lens implants when cataract surgery is performed. This should be discussed with the treating physician prior to the cataract surgery.
Indoor lightbulbs must be swapped for UV-free bulbs like incandescent and LED bulbs.
Insufficient light may pose a safety hazard but can also affect the quality of work, especially if precision work is required. Poor lighting can also cause eye strain leading to discomfort and other health related complaints like headaches.
When assessing how much light is needed for different situations and activities, the following should be taken into consideration:
- The demands for speed and accuracy of the task being done
- Is the surface reflecting or absorbing the light?
- What does the general work area look like?
- What is the individual’s vision acuity? Adequate general lighting is usually between 500 and 1,000 lux (lumens per square metre) when measured at 76 centimetres (or 30 inches) above the floor.
In South Africa, the Occupational Health and Safety Act, Act 85 of 1993 provides the minimum average values of maintained illuminance in different workplaces under the Environmental Regulations for Workplaces. One can also refer to IESNA Lighting Handbook: Illuminating Engineering Society of North America for guidelines on workplace illuminance.
Glare is a term that is used when a bright light source or reflection interferes with how a person sees an object. In most cases, a person’s eyes will adapt to “insufficient light may pose a safety hazard but can also affect the quality of work, especially if precision work is required”
the brightest level of light causing eye strain and decreasing a person’s ability to see as the details in the duller or darker areas become faint. There are two types of glare:
- Reflected glare
- Direct glare Reflected glare is caused by the following:
- Light that is reflected from shiny or polished surfaces
- Monitors and screens
Direct glare is caused by the following:
- Very bright light shining from poorly positioned light fixtures
Contrast is the relationship between the luminance of an object and its
background. Contrast problems occurs because of one of two reasons:
- If there are different light levels from one area to another, and
- If there is contrast between the colours of objects
The immediate work area should be brighter than the surrounding working area to prevent the worker’s attention from being distracted away from the work area.
Poorly distributed light
When parts of the ceiling and/or general surroundings seem dark and gloomy, one can assume that light is poorly distributed causing workers to have trouble in visual acuity or to see properly. To correct this, one should replace light fixtures with ones that distribute some light upwards, paint the ceiling and walls in light colours that will reflect the light and clean the ceilings, walls and light fixtures on intervals depending on the type of environment. Some environments may need more regular cleaning than others.
Approved Inspection Authority
For an employer to ensure that the working environment is safe and does not pose any risks towards the health of its employees pertaining to illumination in the workplace, the employer must measure the employees’ exposure and compare these results with prescribed standards on illuminance. This “monitoring” process must be done by an Approved Inspection Authority (AIA). Two types of illuminance should be measured:
- Luminous flux (measured in lumens) as a measure of the total “amount” of visible light present; and
- The illuminance as a measure of intensity of illumination on a surface
Illumination surveys should include conducting day and night-time surveys as well as test the efficiency of emergency illumination installations. The AIA will measure the lighting levels with a lux meter and provide the employer with a report on the measurements with recommendations after completion of the surveys.
Good lighting increases productivity and is an important factor in assessing general health and safety in the workplace. Illumination risk assessment should form part of the health, safety and environmental risk assessment of a company and objectives and targets should flow from the risk assessment depending on the outcome of the assessment.