Depending on which articles you read, it could very well seem that the lighting is the cause of the problems. However, in today's complex work environment with varying tasks and illuminance requirements, the answer is not so simple. There are many factors in today's work environment that did not exist even 10 years ago. Of these factors, several lighting and non-lighting related conditions affect the potential onset of eyestrain and temporal headaches. The type of work, the tasks performed and the needs of the people within a work environment have dynamically changed and altered. The demands on your lighting system have also changed.

Major potential causes of eyestrain and headaches include: contrast, reflected glare, inadequate illumination, layout of the lighting system, placement of work stations, and tasks performed. While it is unusual for all of these factors to be present, it is quite common that more than one of these factors to exist in a work environment.

Contrast

This is where many of the headache and eyestrain problems can start. The eye is a muscle. Each time the eye looks from one object of a set illumination to another object at a differing illumination level, it must adjust for the brightness and the contract between the two objects. The more often the eye muscles need to adjust, the more tired they get. Tired eyes can lead to eyestrain and temporal headaches. In today's work environment, the eye must adjust to the contrast between many differing visual tasks; general open space illumination, reading printed material, VDT screens and infiltration of natural sources. All of these impact the visual environment and increase the strain on the eyes.

Reflected Glare

Glare can result from both artificial and natural light sources. Reflected glare occurs when, directly or indirectly, light or images are reflected into the eye. This can be as light bouncing off of paper or other objects, or shadow images of luminaires reflecting off of computer screens. Regardless of the source, reflected glare causes the eye to "squint" to reduce the amount of glare entering into it. This is very tiring and also may affect a worker's ability to properly concentrate of the tasks at hand.

Inadequate Illumination

In the past, lighting systems had one task to perform: offer even illumination to all areas of a facility. This was an acceptable practice when buildings were designed and built more than 15 years ago. At that time the recommended light levels were between 70 and 100 footcandles. The advent of the computerized office has put new demands on your lighting system. Your lighting system is expected to meet three different lighting criteria: 50 footcandles on the desk, 30 footcandles for general lighting and 10 footcandles for computer related work. Can one lighting system meet the varying needs of these conflicting task requirements? In reality, it can't. As a result, many work environments are dramatically over lit. This increases contrast and reflected glare, which all contribute to the problem of eyestrain.

Layout of the Lighting System & Placement of Work Stations

As with illumination levels, the layout of the luminaires within a lighting system also greatly influences the resulting illumination levels on the tasks and the glare angle of the space. Many older work spaces have undergone several floor plan renovations. However, the placement of the lighting is frequently left untouched. As a result, the positioning of the lighting in relation to the tasks can be inadequate. A static lighting layout in a dynamic or changing floor plan area frequently results in some areas being over lit and other areas being under lit. Both of these conditions have contributory influences on eyestrain.

Tasks Performed

Lighting levels for computer related work tasks are quite different from general work environment illumination levels. This has significantly increased the potential for eyestrain and headaches for workers in these areas. The computer screen, VDT, is a light source. This creates a contrast problem when viewed in relation to other objects. It is also highly reflective and is susceptible to reflecting images of luminaires shining on or near the screen, thus creating a glare factor. In an environment where the lighting system was designed over two decades ago, for a paper task based work environment, the introduction of computer screens has created problems both unique and bothersome.

Example

Prism performed a lighting system upgrade where one worker's office was identified as a serious problem. For nine years this person had suffered headaches on an almost daily basis. Our audit revealed that the luminaires were grouped together over the task area with light levels ranging from 45 footcandles away from the desk to in excess of 150 footcandles in the task area. After reviewing the client's original plans for the site, it was discovered that the office was not part of the original layout. Renovations to the site had resulted in the office being created as an after thought and that the lighting had just been "put there" to light up
the space. The lighting layout was adjusted with the luminaires being repositioned and properly separated. The result of the adjustment was that the office had an even illumination of just over 55 footcandles. But most importantly, the worker has not suffered further headaches due to lighting issues.

Is There a Solution?

The factors listed here vary in intensity and influence from area to area, from task to task and from worker to worker. Not all of the factors listed here exist in all problem areas. As a result, there is no one solution that works for all situations. There are many products on the market such as different lenses, light sources and tube filters that promise to correct all your lighting problems. However, there is no panacea or cure-all for the problems of eyestrain and headaches. If your facility is over 15 years old, has undergone renovations, and has introduced computer based tasks, your workers could be suffering from the affects of eyestrain and possibly even headaches. A comprehensive review of your lighting systems may be a proactive step in correcting areas of concern before they can become problems and potentially impact productivity.