How to position your computer screen to reduce eye strain and improve posture
The best placement of your computer monitor height, angle and distance depends on your individual physical characteristics and abilities as well as the nature of your task. The right position can help reduce strain to your eyes, neck and upper back.
Monitor distance from the eye
The best distance from which to read a computer screen is generally greater than reading distances for papers and books. Typical distances for reading from a paper or book is from 15" to 25". Computer screens should be further away, sometimes 30" or more.
Maximum viewing distance: First of all, there is no maximum viewing distance. As long as you can comfortably discern the information on the screen it's not too far away. Maximum viewing distance is limited only by the size and clarity of the characters on the screen. Guidelines which specify a viewing distance of, say, 24" to 30" are misleading. The "arm's-length" recommendation for screen placment has even less basis - there is no physiological correlation between visual capability and arm length.
Minimum viewing distance: How close is too close depends on your Resting Point of Vergence (RPV). That's the distance at which your eyes converge with no stimulus for convergence, like in the dark. Studies show that people with far Resting Points of Vergence are less able to tolerate close viewing distances. Interestingly, people with short RPV's have no problem with farther viewing distances.
The RPV averages about 45" looking straight ahead and about 35" at a 30° downward gaze angle. Someone with an RPV of 15" might not have a problem with a 15" viewing distance which would cause eyestrain for someone with an RPV of 50". We commonly see inadequte distance between a computer user and their computer screen, even at "arm's length" positioning.
Place your computer screen as far away from you as possible, The greater the distance the better it is for your eyes, as long as you can comfortably view the image detail. If possible, you should also tip it back so the top of the screen is farther from your eyes than the bottom of the screen. Monitors are best viewed when tilted up a bit, however in this position, the screen may reflect overhead lights.
Laptop computer screens are too small for ideal screen placement at standard image resolutions. It is often necessary to use the "image zoom" feature to enlarge the image the laptop screen to reduce eye strain. In addition, we recommend that laptop users plug in a standard monitor for prolonged use.
Most desktop surfaces are too shallow for proper placement of a conventional CRT monitor. CRT monitors require a deeper desk, or the monitor needs to extend over the back edge of the desk, or you'll need to place your monitor on a separate table placed behind your desk. In an office setting, two workers could place their desks back-to-back, with each worker's monitor could be placed on the other worker's desk.
Flat panel monitors allow more distant placement of the computer screen on shallow desks.
Don't overlook other factors, such as glare, luminance balance, screen contrast, mental stress, and refraction. Some people need corrective eyeglasses or a different prescription for more comfortable viewing.
Monitor lateral viewing boundaries
The work station should enable the computer screen to be located directly in front of you. If you use more than one monitor simultaneously, your main screen should be placed directly in front of you, with secondary screens to the side. The lateral viewing boundaries of the computer or reference documents should not exceed 30° either side of your body mid-line.
You should be able to view the entire VDT screen at a position somewhere between horizontal eye level and 60° below eye level, preferably at a position between 20° and 50° below eye level. Monitor height may be lower if you use bifocals, prefer to work in forward postures, or have a rounded upper back posture (i.e., thoracic kyphosis). Monitor height may be higher if you work in a very reclined posture.
Monitor and keyboard position relationship
Heavy data entry and transcribing of information from paper into the computer may require a document holder positioned directly behind your keyboard and the monitor positioned to your side. For less demanding paper reference, in-line positioning is best, withe the documents positioned on a stand between the keyboard and screen. For operations which are dialogue in nature, the keyboard is placed directly in front of the monitor.