Anyone who has driven a car in the late afternoon knows how light can increase the risk of accident and reduce ability to perform a task. At work, in addition to safety and efficiency, too much — or too little — light can also affect eye health. Straining to see throughout the day can cause problems from burning eyes to headaches.
It is important, then, for managers and workers to pay attention to light and know how to identify signs of insufficient or excessive lighting. On the bright side, getting the right amount of illumination may just be a screen or task lamp away.
When lighting is insufficient for the task at hand, a person has trouble focusing and must strain to see, says Gerry Culina, manager of general health and safety services at the Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton, Ont. One of the most common effects of eye strain is eye irritation. Poor lighting can also cause dry or burning eyes, blurred vision and headaches.
“Many times, eye strain, blurred vision or any type of strain over a period of time can develop into a headache, which can be debilitating for people,” he says.
Lighting should be appropriate to the task being performed and it is important, Culina adds, to thoroughly assess lighting if a worker is suffering from eye trouble or headaches.
According to a checklist provided by the CCOHS, the signs of proper lighting include: no troublesome reflections; no glare along or near normal line of sight; lamps covered to diffuse light evenly; adequate lighting of upper walls and ceilings; and no shadows on work surfaces.
One way to improve inadequate overhead lighting is to use a combination of general and task lighting, Culina says. The desk lamp is especially effective for anyone required to do fine work or read a great deal. Workers can use the lamp to highlight a specific work area — for example, where papers are located — and rely on the overhead lighting to look at their computer, which itself emits light.
“The papers require a different kind of light than the computer requires. So task lighting allows workers to see in the area in which they’re working — their desk. But they don’t have too much light over their head to look at their screen,” he says.
While insufficient lighting clearly makes tasks more difficult and reduces productivity, there is no evidence it causes long-lasting damage to the eyes, says Dr. Shaun MacInnis, president of the Nova Scotia Association of Optometrists.
“It doesn’t physically harm the eyes. A person can get the eye strain, the headaches, the burning, but these are temporary effects and we can fix them,” he says.
Too much light can also cause difficulty, says MacInnis, by creating glare that reduces ability to see. Excessive light or a light source that’s too bright will cause reflections to come off surrounding surfaces — producing an effect similar to that which a driver experiences when driving into the setting sun.
“Trying to do whatever your task may be becomes a lot more difficult with glare bouncing back into your eyes. Of course, it’s difficult too, if the light is shining directly into your eyes, but it’s the reflections that people tend to forget about,” he says.
Many factors affect the amount of reflection and glare in a room. One major factor is colour, MacInnis says. A pure-white area does not require much added light but will reflect a lot of light off walls. In contrast, an area painted dark, such as a warehouse, has much less reflection but may seem so much darker that workplace light becomes inadequate.
“You need to be aware that everything, between the lighting and the walls, plays a role — as well as the materials you’re using because some will reflect more than others,” he says.
Culina agrees, adding a matte finish on walls, floors and furniture will also reduce eye strain and visual fatigue.
“A high-gloss floor, or high- or semi-gloss paint on walls, can really increase the reflectivity of light. So, where there was no problem before, now all of a sudden, workers are exhibiting eye strain because the tables they’re using have a high gloss finish on them,” he says.
Many companies, Culina adds, rely on blinds to reduce the effect of bright sunlight. However, depending on the time of year and location of a workstation, blinds may not actually cut off enough light, and an adjustable secondary screen should be installed.
Artificial lights, such as fluorescent or sodium tubes, are high-efficiency but produce an intense light that generally needs to be buffered, he says. This is often done by fitting them with filters that diffuse the light and produce a “softer” effect.
In addition to affecting eye health, poor lighting can cause other health and safety hazards. There is, for example, a higher risk of musculoskeletal injuries, Culina says. Leaning in one direction to get out of direct sunlight creates unnatural postures that may lead to a stiff neck and pain in the shoulders, elbows, hips and back.
Poor lighting presents additional challenges to workers with low vision, says Roxanne Hazell-Blackman, a low-vision specialist at the Canadian National Institute for the Blind (CNIB) in Toronto. Inadequate light makes printed material and computer screens more difficult to read, and too much reflective glare makes monitors harder to see. Many people complain about fluorescent lights because they flicker — irritating and tiring the eyes — or because they provide insufficient light.
For many low-vision workers, she adds, the additional light provided by a task lamp or under-cabinet light makes a huge difference, causing eyes to strain less and improving workers’ ability to see.
Each worker’s situation is very individualized, Hazell-Blackman says. On an employer’s request, the CNIB will conduct a workplace accommodation.
“It may be a matter of rearranging a person’s workstation in relation to the windows or the overhead lights. We find out what their needs are and see how we can address them,” she says.
Dr. Ralph Chou, professor emeritus at the School of Optometry and Vision Science, University of Waterloo, says all workers, and especially those who must read a lot or perform near-tasks, should take brief breaks throughout the day. A convenient metric is the “20/20” rule: every 20 minutes, look away from your work for about 20 seconds.
“For younger folks, it means they can work a little more efficiently because they’re not stressing out their eyes’ focusing mechanisms. For older workers, it’s a break away from concentrating on what you’re doing. The break relieves the tension of trying to focus,” he says.
While LED and plasma computer screens have eliminated some of the problems that CRT (cathode ray tube) screens presented, Chou says, users should still take measures to guard against eye strain and fatigue.
Computer monitor brightness, for example, should be adjusted to avoid an overly bright screen, which produces after-images and increases eye strain. Displays should also be checked regularly to make sure they are operating properly and ensure brightness and contrast settings are adjusted for the individual worker.
Today’s larger screens and fonts help improve the visibility of text on the screen and makes work easier, Chou says. But remember to clean dust and dirt off the screen frequently. The constant touching on touchscreens leaves fingerprints and dirt, and the dirtier screens are the more difficult they are to see.
Proper placement of the computer display, Chou says, will help to reduce visual fatigue. The workstation should be designed so a worker can sit or stand comfortably and can look slightly downward at the screen. And again, users should look away from the screen for about 20 seconds every 20 to 30 minutes.
Placing the monitor parallel to overhead lights will help reduce glare on the screen, says Culina, adding he does not recommend the use of anti-glare screens.
“Anything between the operator and screen compromises the quality of the images. It’s far better to control the glare by proper lighting design and placement of the monitor,’ he says.
It is important, Culina adds, for managers to talk to workers and ask whether they are having problems seeing their work. Workers may be aware of difficulties but, thinking the problems are unfixable, don’t report them.
“They thought there was nothing anyone could do about it,” he says. “But if we assess the risk and eliminate or minimize it, we can work longer, smarter and safer.”
For the CCOHS checklist, go to