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Dyslexia and Visual Stress
Factsheet 2:  Display Screen Equipment, Visual Stress and Computer Vision Syndrome

Anti-Glare Screens and lighting

There are many anti glare screens on the market, the best-known probably being Kensington Screens, which are widely available online and in High Street stores. In addition to using a filter, ensure that other basic conditions are also met in order to minimise eye strain:

  • Reduce glare from windows (and other light sources) by ensuring that your monitor screen is placed at a 90 degree to them.  Although screen glare is reduced if you directly face the light source (with the light source thereby behind the screen), the high contrast of light could result in eye strain.
  • Close the curtains or blinds until  the sun is no longer shining directly through the window.
  • If this is in your control, use wall paint with a non-reflective surface, and avoid using bright whites and other  highly reflective colours. If not, ask if you can have posters and /or a wall planner (in relaxing colours) on the wall behind you on either side of your workstation.
  • Install light fixtures next to or parallel to the workstation. Do not have your light directly behind you.
  • Rest the eyes regularly ; try and move away from your computer at least every hour. The  eye muscles are like any other muscle in that they can become strained and fatigued if they are not rested.
  • Lighting : ensure that flourescent lights are fitted with the correct diffusers and comply to health and safety standards
  • Clip  the papers you are copying to your monitor or  use a copy stand, to keep your focus on the same plane. Repeatedly shifting from horizontal to vertical planes as you work increases eye fatigue, and also puts an increased load on the working memory. This is a particular problem for dyslexics, but can also be a contributory factor in causing VDU related workplace headaches.

Anti-glare screens such as the Kensington filters may increase comfort by reducing glare from reflections on the computer screen, but they do not reduce the visual problems related to the constant refocusing of your eyes when you work at a computer. Also  the reflective attributes of the white background are not removed by a propriety anti-glare screen, and will still result in visual stress symptoms being experienced by many users.  A  Crossbow monitor overlay in the right colour reduces both the reflective and the optical glare, minimising eyestrain and reducing or eliminating the symptoms of visual stress.

Where an anti-glare screen, such as a Kensington filter, is preferred or already in use, the Virtual Coloured Overlay software used in conjunction with the anti-glare screen  will complete the user's protection against eye strain.

Is Computer Vision Syndrome the same as Visual Stress?

Computer Vision Syndrome is not the same as Visual Stress, being prevalent to some degree among the majority of people who use the computer for extended periods on a daily basis (see below). For visual stress sufferers, the underlying symptoms will remain after practical steps to remove the causes of CVS have been removed. Everybody who suffers from Visual Stress is likely to experience Computer Vision Syndrome, but not everyone with CVS is a Visual Stress sufferer. However for the 20% who are, the symptoms are likely to be exacerbated if they are not addressed.

Computer vision syndrome (CVS)

Computer Vision Syndrome is a complex of eye and vision problems that are experienced during and related to computer use, is a rapidly growing repetitive strain disorder affecting up to 90 percent of workers who are using computers for more than 3 hours per day. Computer eye strain and computer vision syndrome are caused by the way our eyes and brain react to characters on a computer screen. Characters on a computer screen don't have the same degree of contrast and definition as printed text: they are created by combinations of tiny points of light (pixels), which are brightest at the centre and diminish in intensity toward their edges, making it more difficult for our eyes to maintain focus on the images. Instead, our eyes tend to drift involuntarily to a reduced level of focusing called the "resting point of accommodation" (RPA), and then strain to regain focus on the screen. This continuous flexing of the eyes' focusing muscles creates the fatigue and eye strain that commonly occur during and after computer use

The human eye is that of a hunter-gatherer spieces (98% of all humans are born farsighted), and the human body is designed for movement.  Our eye muscle systems are in their most relaxed state when we use our vision for distance objects and space, and it is unnatural for us to maintain a sitting posture for long periods of time. As a result, working at a computer for a long period of time without breaks can cause unnatural strain and other cumulative negative effects on the user including the worsening of farsightedness, nearsightedness, astigmatism, eye-focusing disorders and poor eye coordination.

Common symptoms of CVS are:

  • Eyestrain
  • Blurred vision
  • Difficulty concentrating
  • Headaches
  • Red, dry or burning eyes
  • Increase in nearsightedness
  • Slow refocusing
  • Excessive fatigue
  • Neck, shoulder and back pain

Causes:

  • Extending short distance focusing
  • Reduced average blinking time
  • Poor lighting
  • Poor posture

Limited awareness of Display Screen Equipment Hazards

University of Sheffield and UMIST conducted a stress survey on call centre workers for Health & Safety Executive (HSE) entitled "Psychosocial risk factors in call centres: An evaluation of work design and well-being".  As well as the stress factors involved in handling calls an exploratory study also pinpointed a range of other hazards that could also risk both the psychological and the physical well-being of call centre employees. These included display screen equipment, and call waiting information displays. Potential hazards specific to vocal and optical health were also highlighted. The study found that the understanding of good practice in relation to DSE, not only amongst frontline call handlers but also by managers and health and safety advisors, was sometimes very limited.

NHS Healthy Scotland and Visual Stress

NHS Healthy Scotland has a leaflet on Visual Stress available on the link below. In fact they have gone as far as to introduce this leaflet for potential sufferers to take to an optometrist (usually called an Orthoptist in Scotland) for an eye check to determine which colour overlay is the most effective. The leaflet states: Some people experience Visual Stress (referred to in the leaflet as Meares Irlen Syndrome, or MIS) symptoms after reading for a short time: others find that it takes longer for the symptoms to occur. The severity of symptoms also varies from person to person: the more marked the symptoms, the greater the barrier to successful reading. It is more common in children and adults with specific learning difficulties but it is thought to exist in a surprisingly large number of normal readers. In both groups, the symptoms of Visual Stress can prevent an individual reaching their maximum potential in education/ occupation.

NHS Healthy Scotland, Visual Stress Leaflet

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