Computer Health Information - Eye Strain

The Biological Facts

Human bodies have evolved over hundreds of thousands of year to function certain ways based on environmental influences.  Only in the last couple of hundred years have we done so much “near work” which causes eyestrain. The muscles responsible for moving our eyes around – left and right, and up and down - are not likely to be strained by computer use.  The two groups of eye muscle can become strained when working with a computer are the ciliary muscles, and the muscles responsible for convergence.  The ciliary muscles change the shape of the lens for sharp focus on the retina (a function called accommodation). So think of the ciliary muscles as the "focus muscles".  The muscles responsible for convergence are the ones that turn both eyes in at the same time, toward our nose, as we focus on things close to us (this is when we go “cross-eyed”).

Eye Strain

Like all other muscles, the ciliary muscles of the eyes will get tired if they maintain the same state of contraction for an extended period of time.  When we sit in front of the computer there is no need for these muscles to expand or contract, since the focal length at which we are looking is not changing.  Regularly looking up from the screen and focusing on objects at different focal lengths away relieves the strain.

Viewing Angle

Based on the way we evolved, it turns out that both accommodation and convergence are easier when we are looking slightly downward.  So is it is best to have the computer monitor positioned slightly lower than eye level (an angle of around 15o is suggested).  Though you are looking slightly downward, do keep your head upright and balanced, not tilted forward which puts stress on your neck.

Monitor Distance

When our eyes have nothing in particular to look at, they will focus approximately 30 inches away.  As we look at things very close to us, convergence becomes very straining – think of the discomfort of going cross-eyed. The implication of these two facts is that the monitor should not be placed too close to you.  In fact you should have it as far away as you can manage while still being able to read what’s on the screen.  Changing the monitor’s resolution or increasing the zoom level of an application can help you position the monitor further away.

Dry Eyes

For some reason we blink less often when looking at a computer monitor compared to other activities.  And so our eyes get drier than they should be.  Lowering the angle at which you are looking at the monitor actually also helps this problem, because your eyelids partially close when you look down.  Trying to be conscious about blinking more, and increasing the humidity of your work environment are two other solutions to prevent dry eye problems.  A simple humidifier, like the one in the lab, is very helpful. And if your eyes become irritated for whatever reason, just closing them for a while can do wonders. The other thing you need to do is drink plenty of water, a good, healthy thing to do regardless.

Glare, Lighting & Brightness

Glare can be irritating to your eyes in addition to being annoying.  You can reduce glare by adding blinds to windows, or drawing curtains closed, and keeping them closed with a clothespin.  Often, placing your computer right beside a window can be the best location, not only for reducing glare, but to help relax your eyes by looking out the window occasionally. (Though if you can’t totally get rid of glare, you can actually use it to help relieve eyestrain by, focusing on an object reflected in the glare, which will change the focus of your eyes.) Also, assure a well-lit working environment, i.e. with good "ambient" light in the background. And make sure you keep your monitor at a good level of brightness; don't sacrifice your eyes due to bad re-charging habits!

But at the other extreme, beware (from my personal experience a short while ago) the following situation. Avoid working on your laptop outside in bright conditions - for example, under the "shade" of a palm tree next to the beach. The sun, or reflected sun, can be a major irritant of your eyes, especially if you are not wearing good quality polarized sunglasses, not blinking a lot, and staring at a screen.

You can also check out "gaming glasses", such as the ones produced by Gunnar, to help relieve eyes strain from these issues.

Added 2021, to edit, research more, and improve: Dark mode about "cool", not about eyes health. The iris is a muscle, and so being either dialated for an extended time, or constricted for an extended time, will cause strain. And either too dark or too bright will do this. So dark mode in a dark room at night is bad. There's the dynamic of contrast between dark and light, so that if it simply is dark, a darker monitor can help; but the better overall option for computer work is a well lit environment, matched with adequate monitor brightness. And note that you have a double-whammy with dark mode in a well lit classroom; both the edge contrast causing stress on edge rods & cones, and excessive dialation of pupils, at a time and place when that's the last thing that should be the problem.

Angle of Monitor

Studies have found that eye discomfort and strain occur when the top of the monitor is tilted forward.  When the top of the monitor is tilted back, eyestrain is less.  But glare should also be reduced.  Do note that none of the suggested changes stated in this document should be made at the expense of others; moderate correction to all factors is best.

Monitor Adjustments: Brightness (and Refresh Rate)

If you find your eyes irritated or tired, an easy thing to try is adjusting the brightness of the monitor up, or down. You may have to strain your eyes if the monitor is not bright enough, and if too bright, that can irritate your eyes as well.

Another thing you may be able to adjust on your monitor is the refresh rate It is the number of times per second that the pixels on the some monitor’s surfaces are re-energized. Many older monitors, and some new ones have a refresh rate - check in your Monitor/Display control panel.  Lower refresh rates can make the monitor image seem like it is vibrating, which may cause eyestrain.  So if your Monitor/Display control panel will allow you to increase the refresh rate, doing so can help ease eyestrain.

Other Adjustments/Apps & Utilities

There are other various adjustments you can do via the operating system and certain applications. For example, in the Mac OS X, you can reverse the colors of the screen (black/white), or use grayscale, by going to the Universal Access System Preference. And Microsoft Word has a feature in the general preferences in which you can give yourself a blue background, if this helps ease eye strain.

Many multimedia applications also now have the option to use a "light" or "dark" environment, for example the Adobe products, like Flash and Photoshop. A darker screen may be better for your eyes, though every person is different.

There are now applications such as f.lux, which adjust the "color" of the light being given off by your monitor according to the time of the day. So, for example, there is more "blue" light in the middle of the day, and less at night. Not only can this help your eyes, but it can help you get to sleep more easily, since your eyes are not exposed to "day" color light if using the computer late into the evening.


Implications & Suggestions For Eyes:

1. Number one is take breaks:
Momentary breaks – look up from the monitor every few minutes at least
            Mini breaks – every half an hour or so, get up and stretch for 5 minutes
            Regular breaks – totally change your activity from the computer
2. Place your monitor low enough so you can gaze down around 15o
3. Tilt the top of your monitor back
4. Place your monitor as far back as you can while still able to comfortably read text on it
5. Try to be conscious of blinking regularly
6. Assure a well-lit environment
7. Reduce glare
8. Increase the monitor’s refresh rate
9. Get a good night's sleep - your eyes, like the rest of your body, need it

A cute video about computer eyes health.


You are likely to listen to music often while at a computer.  Keep in mind that headphones area a major cause of hearing loss, when used inappropriately.  The problem is that the source of the sound is right next to your eardrum.  So even though tiny ear-buds can seem harmless when compared to the thundering speakers of dance clubs or concerts, headphones played loudly can be just as damaging, or even more so.


Colds & Flues & Public Keyboards

When using a public computer (including a school computer lab), keep in mind that germs can be spread effectively by way of keyboards and mice.  Hands that have been coughed onto, and which then work with a keyboard and mouse, can make an efficient means for germs to be passed on.  Therefore, particularly during cold and flu seasons, the good idea to wash your hands before eating is wise after working on public access computers.


Computer Health Conclusion

There are many health issues you need to keep in mind when working on a computer.  Some problems can arise quickly, and others accumulate over time.  The biggest point to consider as young people, is that you are now in the process of forming habits you will maintain for a life-time.  If you are conscious about each of these health issues now, then once good habits are formed, you will no longer need to think consciously about them.  Conversely, if you form bad habits now, they will be hard to break, and will result in pain, discomfort, and possible disability, in the future. 

Making healthy adjustments now could be said to boil down to:
- a bit of will power, leading to good habits (which once formed are easy to keep), all aided by a few initial, strategic ergonomic purchases.



And don't forget your favorite Health Mantra (sung as a round):

Wrists up, Look up, Shoulders Back.

Break, Break.... Break Break.

You've had e'nough', 'nough, na-na-nough.