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Home > Issue by Date > February 2008

Just The Right Fit

Flexible options for display monitors can help to improve user comfort and productivity.

By Thomas J. Albin, P.E., C.P.E.

People like variety. Whether it’s a preference for a sports team or for clothing colors, every individual has his or her own personal likes and dislikes.

So it should not be surprising to the astute facility manager (fm) that computer users express a variety of preferences for the placement of their computer monitors with regard to height and distance. They want to be able to adjust the position of the monitor during the course of a workday to maintain their comfort levels as tasks change. In fact, it is not uncommon to find differences between users of as much as 14" in the preferred distance from the eyes to the front of the screen, and differences of as much as 10" between individuals with regard to the preferred height of the monitor.

Streamlined Screens

In the past, the weight and bulk of Cathode Ray Tube (CRT) displays made it difficult to adjust monitor positions quickly and easily. However, in the last few years, lighter, more compact flat panel monitors have begun to dominate the market.

Their lesser weight, bulk, and standardized mounting designs have facilitated development and increasing utilization of user adjustable monitor supports. These adjustable monitor supports offer individuals the ability to position the monitor easily in accord with his or her own comfort preferences.

Ergonomic research and experience support individual preferences for monitor position. Two of the most commonly expressed types of discomfort among office computer workers are visual discomfort and neck and shoulder pain. And monitor placement plays a key role in causing/alleviating these symptoms. [See Ergonomics in Computerized Offices by E. Grandjean (New York: Taylor and Francis, 1987).]

A monitor that’s too high (relative to the user) generally causes users to bend their necks back in order to look up. A monitor placed too low causes the user to bend the head and neck forward. Bending the neck and head back (extension) or forward (flexion) more than a slight amount becomes uncomfortable, due to the strain on the muscles of the neck and shoulders.

Similarly, the height and distance of the monitor can affect visual discomfort. The screen may be too close, causing discomfort as the eyes try to focus on it.

Conversely, the screen may be too far away for the user to read or see what is displayed. This often causes the user to lean forward to read the screen, subjecting the user’s neck, shoulders, and eyes to discomfort.

A monitor that is placed too high results in an upward gaze angle, exposing more surface of the eye. Because more surface of the eye is exposed, more of the tear layer that protects and lubricates the eyeball evaporates and leaves the eyes feeling dry and irritated.

Just Right

To paraphrase Goldilocks, some monitor positions are too high, some too far away, and some are just right. Finding the just right location makes the user more comfortable and productive.

The variation in users' preferences regarding monitor height is influenced by several variables. One obvious reason for this unpredictability is that people come in different sizes. For instance, when a tall man is seated, his eyes can be more than 36" above seat height, while a small woman’s eyes may be about 26" above seat height.

Accommodating this height variation is critical to the user’s comfort. A poor match between the monitor and the user’s height is commonly associated with ergonomic complaints.

It is perhaps less intuitive for monitor height to be adjustable independent of the work surface (e.g. where the keyboard sits). This is because, while there is about 10" of difference in seated eye height between a tall man and a small woman, there are only about 5" of difference in seated elbow height between the two. (Work surfaces are generally located at elbow height to minimize postural discomfort). Consequently, a monitor sitting on a work surface requires additional height adjustment in order to provide a range of monitor heights that will accommodate a wide variety of users.

Common practice has been to instruct computer users to adjust the monitor height so the top of the viewing area is at (or slightly below) eye level. More recently, a new American National Standard, ANSI/HFES 100-2007, Human Factors Engineering of Computer Workstations [available online at www.hfes.org/Publications/ProductDetail.aspx?ProductID=69], recommends that the monitor height should be adjusted so the center of the screen is about 15° to 25° below eye level.

A simple way to estimate this angle is to measure the horizontal distance between the user’s eyes and the front of the screen. The center of the viewable area of the screen should be no more than half that distance below the user’s eye level.

The Right Distance

A good rule of thumb is to place the monitor an arm’s length away from the user. This is consistent with ANSI/HFES 100, which recommends that the minimum monitor viewing distance should be at least 20" from the user’s eyes.

The maximum viewing distance is generally limited only by the space available and the size of what is displayed on the screen. To determine whether a type or font will be readable for a given viewing distance, ergonomists typically use the James Bond 007 rule. This says that, to be legible, the height of the character on the screen should be about 0.007 times the viewing distance. For a viewing distance of 20", a 12-point type font, which is approximately 1/6" high, meets this requirement.

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Special Placement Cases

One special case of monitor placement occurs when a laptop or notebook computer is used for extended periods of time as an individual’s primary workstation. Because the display and the keyboard are integrated into a single unit, it is generally difficult, if not impossible, to place the laptop so that the eyes, neck, shoulders, arms, and hands are simultaneously comfortable. If the laptop is placed so that the monitor is at an appropriate height and distance, the shoulders, hands, and arms are likely to be uncomfortable due to the long reach to the keyboard; if the laptop is placed so that the keyboard is appropriately located for hand arm comfort, the eyes, neck, and shoulders are likely to be stressed.

Consequently, supports have been developed for laptops that allow the screen to be placed at the appropriate height and distance. Hand and arm discomfort are avoided by using auxiliary keyboards and input devices as supplements to the built-in input devices.

Sit/stand workstations are a second special case for adjustable monitor supports. Alternating between sitting and standing while working can be very beneficial, particularly for back comfort.

Clearly, monitors (and input devices) need to be re-positioned when employees change from sitting to standing work positions. As a result, monitor supports have been developed that readily accommodate alternating between sitting and standing work positions.

Accommodating Multiple Monitors

It is becoming more common to encounter situations where multiple displays are in use within a single workstation. While only a small amount of ergonomic research has been conducted in this area, the principles discussed in this article can be applied here as well, especially those regarding monitor height and distance. Whether looking at one display or three, an employee who is looking at a display that is placed at the wrong height or distance will likely experience discomfort.

An issue that can arise with multiple displays is twisting of the neck and head to the side. ANSI/HFES 100 suggests that the monitors should not require the user to look more than 35° to either side without turning the entire body.

To illustrate this, two 19" diagonal monitors could be placed side by side if the user was sitting at least 27" away from the monitors. If more or larger monitors are in use, the viewer should be encouraged to swivel his or her chair and turn the whole body rather than twisting the neck.

Better Comfort And Performance

The lighter weight of flat panel displays and the affordability of auxiliary input devices has made it much more feasible to produce and use display and input supports that adjust for user comfort. Although not discussed in detail here, research has consistently shown that a combination of appropriately adjusted, ergonomic workstations and user training result in substantial productivity enhancements.

According to the Office Ergonomics Research Committee, a recent report of two independent studies of the effect of ergonomically well adjusted offices found that productivity was enhanced by between 10% and 17%.

Although the weight and bulk of older technology displays placed practical limits on the ability to adjust their position to suit individual requirements, the product landscape has changed. New technologies in lightweight, low volume displays, combined with innovative monitor support technologies, allow quick and easy adjustment of monitor position, enhancing user comfort and performance.

Albin, a certified professional ergonomist and licensed professional engineer, is a consultant for 3M Workspace Solutions. He is also a principal at High Plains Engineering Services, LLC and the executive director of the Office Ergonomics Research Committee (www.oerc.org).

Have you changed the monitors in your facilities to accommodate user needs and reduce desk clutter? Share your thoughts by writing to schwartz@groupc.com.

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