One of the most significant changes to the modern office in recent years has been the introduction of computers into the workplace. As a result we spend a lot more time using a VDU screen or computer monitor.
As with many success stories, there have been some unexpected problems. Eye strain and vision problems are among the most frequent complaints while using a computer monitor.
Visual demands on VDU operators
VDU work involves concentration on a task usually between 50 cm to 70 cm away. To see clearly at these distances requires an unconscious effort. Several different muscles are needed when the eyes adjust to focus on a near point. One muscle inside the eye changes the shape of the eye’s lens so that the eye is focused sharply and clearly on the VDU screen. Other muscles turn the eyes inward, directing them to the same point on the screen and moving the eyes quickly from one place to another.
Complaints of VDU operators
Common complaints reported by computer users are:
- blurred vision for either near or far viewing distances
- itching or burning eyes
- tired eyes
- flickering sensations of the eyelids
- double vision
- slow refocussing
- frequently losing their place when moving eyes from printed material to the screen
- difficulty seeing distant objects clearly after prolonged VDU use.
These complaints are symptoms of what is commonly called eye strain or near visual stress.
Furniture, posture and position
The use of well designed furniture and proper positioning of the hard copy can help prevent or reduce VDU operator discomfort induced by VDU use.
Use adjustable chairs that allow the user to set their chair for the most comfortable height and back support.
The top of the computer screen should be 10 degrees (and the centre of the screen 20 degrees) below the user’s eye height. The appropriate distance from the viewer’s eyes to the screen should be approximately 40 to 70 cm.
Reference material should be placed at the same distance from the eyes as the VDU screen. This avoids large head and eye movements which are tiring.
Tips on lighting and glare control for VDUs
Lighting needs vary with individuals, the nature of the task at hand and the layout of the office. It is usually desirable for the VDU screen brightness to be three to four times greater than ambient office lighting. Whenever possible a lower level of general room lighting should be maintained where VDUs are used.
It is not possible to specify the light level which should be used in an office due to the variety of activities which may be carried out at any one time.
Special monitor shields or filters are available which can be fastened to the front of the screen to eliminate troublesome glare and reflection.
Localised lighting sources such as flexible lamps may be used for other desk work. None of the light from lamps should shine directly onto the screen or be able to be seen directly from the computer user.
Avoid white or coloured clothing if it causes a reflection on the screen.
Rest breaks are important because VDU operation often requires intense concentration. If possible work with screen based equipment should be interspersed with other tasks. Rest breaks may need to be scheduled into a work routine if operators do not take sufficient time away from the screen of their own accord. Glancing away from the screen for a second or two every few minutes will make work with VDUs more comfortable.
Poor vision and VDU use – a bad combination
Vision problems that have not been noticed before often become a source of complaint for VDU operators. This is because VDU work imposes greater visual demands than traditional office work.
The Optometrical Association Australia recommends that staff have their eyes thoroughly examined before they begin work with screen-based equipment and then on a regular basis. The examining optometrist should be informed that the person is, or will be, a VDU operator and should also be told of any specific visual problems which the person has experienced.
Wherever possible the distance and angle of the VDU screen at which the operator is working should be described. Proper optometric care can solve most vision problems.
Vision that may affect VDU work
Long-sighted people see distant objects more clearly than close objects, but usually have to make an additional effort in both situations. A mildly long-sighted person who is generally able to perform normal seeing tasks such as driving or reading without prescription spectacles may require them to overcome blurred vision or visual discomfort when working at a VDU.
Presbyopia is a visual condition that is part of the natural aging process and usually is first noticed in the mid 40s. Presbyopia reduces a person’s ability to focus clearly on close work. Reading glasses for use while operating a VDU may be required. If mulitfocals are necessary they must be designed specifically with VDU operation in mind and a measurement of the distance from the operator’s eyes to the screen must be given to the optometrist.
Astigmatism is another common vision disorder that blurs vision at all distances and may cause discomfort to the VDU operator. It is a condition in which the front surface of the eye or cornea is not perfectly round, but is oval shaped. Prescription lenses that are worn only when using a VDU can help operators with mild astigmatism. People with a greater degree of astigmatism may need to wear glasses all the time.
There are many other conditions which make the VDU screen appear blurred, increase susceptibility to glare, or otherwise make VDU use difficult. Among these are poor eye co-ordination, short-sightedness and eye focusing problems. Your optometrist can diagnose these conditions and advise you on treatment suitable for VDU operation and normal seeing tasks.