Avoiding Eye Strain

Avoiding Eye Strain
We have many senses. They are how we interact with the world. Our first learning experiences are through touch. As time goes on, other senses develop. We hear, we smell, we taste, we develop Proprioception (our sense of how the different parts of our bodies relate spatially to each other and how our body relates to the world around us). And we see.

Our eyes are marvelous instruments. More than the other sense, vision is learned. If a person is given prism glasses that make him or her see the world upside down, over a day or two the eyes relearn how to see – and the world is right side up. When the glasses are taken away, the world is upside down again until the eye receptor / brain connection re-sets and the world is back the way it started.

Eyes at Work

We look at our computers for hours a day. Even if part of it seems relaxing (playing solitaire, minesweeper or such), as long as we’re on the computer our eye muscles are working out.

The eye has many sets of muscles. They are matched on each eye, top to bottom and right to left. Large muscles move the eye in the socket and control blinking. Small muscles control pupil size. There is even a surface muscle that completely encircles the eye.

We tend to take our vision for granted. Every time your eyes move or you re-focus these muscles are involved. They must coordinate, not only each eye individually, but the two have to work together. Like every other muscle in your body, they can become overtired.

Generally, we don’t feel our eyes tire. Sometimes, we do. We may give them a break for a second or two. But ocular stress, just like any other muscle stress, can build up over time.

It Pays to Give Attention to your Eyes on a Regular Basis.

If you work all or most of the day at a computer, here are some tips to help those overworked muscles recover.
  • You eyes function best if they change focus distance frequently. Don’t stare at the screen. Stand up and look across the room for a few seconds every half hour.
    • Several times a day, look at things that are far away – out a window for example, and allow your eyes to focus in that more ‘at rest’ position.

  • Position your monitor about 20" to 26" from your eyes (roughly the distance from your eyes to the end of your index finger with arm outstretched).
    • This will help you avoid sitting on the edge of your chair or leaning forward with your neck in an awkward position so that you can clearly see the items on the screen.
    • Other things that may impact proper monitor distance are the size of your screen, your screen resolution, and the size of your actual visual target.

  • Set your screen height so that the top edge is even with your eye level when you look straight ahead.
    • This will seem very low at first, but it puts your eyes in the proper position for the most accurate and relaxed vision.
    • If it doesn’t produce excessive glare, tilt the screen upward slightly so you are not looking at the image appears on a flat plane to your eye angle.. The optimal screen position is 10 to 20 degrees below eye level.

  • Monitor screen resolution, the Internet browser text size, and the zoom and font default in the operating system and in software applications should be set so that text is easy to read. The only exception may be if you are working with objects that do not have text. Then, the ‘handles’ on the objects need to be easily visible (and mousable)
    • For CRT Monitors, start with a screen resolution of 600x800. LCD monitors should be faster, around 1024x768 or higher.
    • Monitor refresh rate should be set at or above 75 hertz (hz) on older CRT models. For LCD monitors the refresh rate is factory calibrated.

  • Blink often. As we work, our concentration will often be extreme and blinking often slows down – frequently to only 7 times per minute. . The average person blinks 22 times a minute. That is very frequent. Less blinking means less lubrication for the eye lens. This can result in real problems.
    • Use an eye moistener (saline solution) if you can't get into the habit of blinking more often. Systane or almost any other eye drop lubricant can help – but get one you can use frequently.

  • Place the palm of your hands over your eyes for a minute or so with a very light pressure. The pressure combined with the heat of your palm warms the muscles around the eyes and helps them relax.

  • Minimize glare.
    • Take a good look at the surface of your screen at different times of day. Notice if there are any visual ‘hot spots’ – places where you see actual reflected light or other bright areas. Try to identify what is causing them.

    • Move your monitor so that you can avoid 'hot spots' or use other items to block the source. Some people have used rice paper on windows, pictures on top of shelves, or other items. Be creative.

    • If there is excessive overhead light, you may want to wear a visor or baseball cap. This works well as an eye shade and often immediately reduces eye strain.

    • Ambient light is another source of glare – but this glare come from all around you. It’s best if the background light level around the monitor is about the same as the screen light level. If the light level is high or uneven, check your desk lighting. In cubicle, the ‘under bin lights’ are often culprits in creating issues.

copyright vhixson, sunnyvale ca 8/23/2011
Safety Daily Advisor [SafetyDailyAdvisor@nl.blr-news.com]

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