Characters on the Screen 

The characters on the screen should be well defined and clearly formed so that letters and numerals may be easily recognised and clearly distinguished. The spacing between characters and between lines should also allow for an easily legible text on the screen. The legibility of characters, which depends mainly on the way they are created, their size and shape, is particularly important for avoiding eyestrain.

A minimum character height of between 3.l mm to 4.2 mm in the 350 mm to 600 mm viewing range – with a maximum viewing range of not more than 700 mm – is recommended.

Image on the screen 

The image on the screen shall be stable, with no flickering or other forms of instability.

In order to keep the characters visible on the screen, the signal must be continuously refreshed, i.e. regularly rewritten on the DSE.

A flickering, swimming or shimmering effect which can arise may be minimised by operating DSEs at a recommended minimum 50 hertz refresh rate.

Contrast and brightness                                                       

The DSE should be capable of adjustment for contrast and brightness by the user to obtain a suitable working condition. This will help avoid eyestrain and should help to maintain the quality of work produced. Excessive contrast between the characters and the general background on the DSE should be avoided.

Dual-Monitor Setup                                                       

As with a single-monitor workstation, the focus of the DSE assessment is on maintaining a neutral neck posture. This can present challenges when you are trying to look at another monitor, or switching frequently between monitors.

Most people with dual monitors lie along the spectrum between 50/50 use and 80/20 use. In those cases, the split of the monitors should be placed along an arc between right in the middle (as in the 50/50 use) and all the way to the side of the dominant eye (such as in the 80/20 use). The more the primary monitor is used, the closer to directly in front of you the split should be.

When working for long periods of time on one monitor, use a swivel chair to physically turn to face that monitor, thus avoiding neck twisting. You should also re-orient your keyboard and mouse so that they are directly in front of the same monitor for the period you are performing the single-monitor work.

What percentage of use for each monitor? If both monitors used equally (50 percent)

1. Position both screens as close as possible in front of you so that their inner edges are touching and are exactly in front of your
2. Angle the screens so that they are slightly concave, creating a semi-circle around you. This will ensure a consistent focal distance between you and the monitors.

One monitor is the primary (>80 percent)

For the primary monitor, follow the steps described for single- monitor setup. For the secondary monitor, place it on the side of your dominant eye.

How to tell which eye is dominant:

1. Extend one arm out in front of you, holding the thumb (or index finger) of that hand in an upright position.

2. Keeping both eyes open and focused on a distant object, superimpose your thumb on that object. It is normal if your thumb appears to partially disappear.
3. Alternately close one eye at a time
4. The dominant eye is the eye that keeps your thumb directly in front of the object while the other eye is closed.