Guest Author - Anne Asher

Monitor set-up affects the eyes and the neck. The distance of the monitor influences posture and musculoskeletal alignment, but is controlled by the eyes. This article discusses the relationship between monitor distance and the eyes.

Monitor Distance
Eyes are the limiting factor in monitor distance. Eyes accommodate and converge in order focus on near and far objects. As you will see, this will help determine how far away to place the monitor.

A survey of research on monitor placement was done by Ergonomist Dennis Ankrum of Ankrum Associates. The review indicated that monitors should be placed as far away as possible with the text still legible and comfortable to read.

According to Ankrum, �If you can read the monitor, it is not too far away. If you can�t read the characters, it�s usually better to make them larger than to bring the monitor closer.�

Accomodation and Convergence

Accomodation
Ankrum defines accommodation as the change in lens shape to allow for focus on a close object. He says that the eyes have a default accommodation distance, which is the distance at which the eyes focus when there is nothing to focus on.

Previously ergonomic guidelines for monitor placement was determined by this default accommodation distance. Now there are other factors being taken into consideration.

Convergence
Research studies have shown that convergence of the eyes is the main determinant for eye fatigue and strain, more than accommodation.

Ankrum describes convergence as:
�when the eyes turn inward toward the nose when we view close objects. Without accurate convergence, we see double images. The closer the objects, the greater the strain on the muscles that converge the eyes�.

Simulate eyestrain
To simulate the kind of eyestrain created by viewing monitors that are too close, try this little exercise Hold your finger out in front of you with your arm fully extended, As you slowly bring it in toward your nose, follow it with your eyes. Do you feel discomfort or strain as your finger comes closer to you face?

OSHA
The U. S. Department of Labor�s OSHA agrees in general with Ankrum�s findings. It differs slightly in the area of longer distances. It warns that in the case of viewing distances that are �too long�, the worker will tend to lean forward to see small text. This causes eye fatigue and will stress the spine, �because the backrest is no longer providing support�. OSHA also says that monitors that are too close can result in awkward body posturing.

Benefits of Monitor Distance
Having the monitor further away rather than closer has shown by the research to have several benefits:
� Accurate clerical performance
� Reduced eyestrain
� Avoiding awkward, non-neutral body postures.

Eye to Screen Distance
The recommended eye to screen distance is 25� inches or more.