Vision is the most powerful determinant of posture at work. It is impossible to maintain good postures throughout the workday, unless work materials and equipment are thoughtfully placed within the line of sight and within a comfortable focus distance. The use of copy holders, slant boards, and book stands have a positive impact on posture, and therefore, on the eyes.
The ideal focus angle
Your body follows your eyes. To preserve proper posture, your visual target should be nearly parallel to your face and within your line of sight. Poor visual target position forces your spine to compensate by bending. This occurs when you try to sit in an erect posture to write on a flat surface.
Ideal reading angles are at about 60°, give or take. If you wear bifocals or if your upper back is rounded, your line of sight may be lower.
Ideal writing surface angles are somewhere between 10° and 20°. This is not ideal for vision and your spine, as both your neck and back will have to bend forward somewhat. However, writing at a steeper angle is likely to strain your shoulder and neck muscles. Artists and draftsmen often find ways to write or paint at steeper angles to protect their backs and necks. Generally, they do better if they can support their arms directly on the writing/painting surface as they work.
The ideal focus distance
Ideal focus distances for reading and writing average between 15 to 25 inches from the eyes. All of us are a little different. If your visual acuity point is at 16 inches, you will strain your body forward to focus on work that is more than 17 inches away.
Computer work In recent times, especially since our dependence on computers has grown, an increasing number of people are seeking medical attention for eye strain and irritation, along with back, neck, shoulder, and wrist soreness. This collection of symptoms has been termed Computer Vision Syndrome (C.V.S.) that describes eye-related and other problems caused by prolonged computer use.
These problems are more noticeable with computer tasks than other near work because letters on the screen are formed by tiny dots called pixels, rather than a solid image. This causes the eye to work a bit harder to keep the images in focus.
There is no scientific evidence that computer screens are harmful to the eyes. A common myth is that eye strain caused by reading and close work is damaging to the eyes. This is not true; however, those who work at computers often experience many frustrating symptoms. This, like other problems related to using close vision, is more a function of the lighting and distance of the screen from the eyes.
Ideal focus distances for computer viewing is greater than for reading and writing. Research suggests there is less eye strain when your computer monitor at least 30 inches from your eyes. In the old days ( just a few short years ago) computer monitor resolution was too poor to allow an ideal focus distance. Newer computer monitors with better resolution can be seen at greater distances, and the text can be made enlarged to make distant viewing easier. However, if you have a traditional box-style C.R.T., your desk is probably not deep enough to allow you to place it that far away from you. If this is your problem, consider a detached keyboard support or place your desk further from the wall and keep the monitor as far back as possible. It would be best however, if you could invest in a new flat panel display or in a deeper desk.
Screen glare problems: Glare makes your screen difficult to see and fatigues your eyes. The glare from a window or overhead light can create a reflection in the screen which obscures the display. In situations where a bright light source (like a window) is behind the screen, the screen contrast can become too dark to see.
Solution: Reorient your screen so that it is perpendicular to the light source (for example, with the window at your side). Or fashion a screen shade or hood from cardboard and tape, being careful not to cover the screen’s ventilation holes. Vertical blinds can let in natural light while shading direct sunlight in your direction. It is best in such instances to purchase a glare screen or hood.