Computer Vision Syndrome and Eye Strain

Using Your Eyes and Your Computer

Studies suggest that most office workers are using video display terminals (VDTs), and most homes, schools and libraries are connected to the Internet. In short, most people spend a good portion of their day staring into a screen of some kind.

It's 11:30 in the morning. You've been working at your computer or video display terminal (VDT) since 9:00 AM. Your eyes feel irritated and fatigued, your vision is blurry and you still have several hours of work ahead of you.

The symptoms you are experiencing are common among people who work with VDTs. Computer Vision Syndrome (CVS) is "the complex of eye and vision problems related to near work which are experienced during or related to computer use."

CVS can cause the following symptoms:

Eye strain (nonspecific eye discomfort)
Fatigue
Headache
Blurred near or distance vision
Irritated eyes
Diplopia (double vision)
Squinting
Excessive tears
Dry eyes

These symptoms develop when the visual demands of the computer exceed the ability of the user to comfortably perform the task. Poor contrast, poor resolution, glare and reflections on the screen can excellerate CVS symptoms, which can also be associated with inadequate viewing distance and angles, bad room lighting, an improperly arranged workstation and excessive viewing. But they may also be, at least partly, the result of a vision problem. Anytime you experience symptoms like those listed above you should visit your doctor of optometry for a comprehensive eye examination. And when you do be sure to tell the doctor about the VDT work that you do.

Most people understand that computer screens can be hard on the eyes; what an eye doctor needs to know is the following:

The type of work performed on the computer;
The size and color of the VDT screen and character;
The number of hours per day;
The severity and frequency of CVS symptoms.

After you have had a comprehensive eye examination, there are a number of things that you can do to arrange and use the elements of your workstation to eliminate or minimize discomfort. Such factors are outlined on the pages to follow.

Factors to consider include:

Workstations should be properly arranged to minimize eyestrain or musculoskeletal symptoms.
Your feet should be flat on the floor (or on a slightly angled foot rest).
Your knees should extend 2 to 4 inches from the edge of your seat and bend at a 90 degree angle.
The distance from the front of your chair to the hollow of your knee should be 2" (5cm) to 4" (10cm).
Your chair should support your legs without excessive pressure on the back of your thighs.
You should sit with your back snug against the seat to fit your spinal contour and your thigh to trunk angle should be at 95 degrees.
The surface of your desk should be 26 inches high by 27 inches deep.
Your arms should reach out to the computer keyboard at a 90 to 100 degree angle.
Your wrist and hand should extend nearly straight from the elbow to the home row of the keyboard.
Adjust your keyboard so it does not lie flat.
The VDT screen should be 20 to 26 inches away from your eyes, and you should be looking down at the screen at a 10 to 20 degree angle.
If you type the printed material into the computer, you should put the material on a holder next to the screen at the same viewing distance as your VDT.
Keep the VDT screen free of dust and fingerprints to ensure clarity.

Lighting Unfortunately, most office lighting is designed to illuminate paper work on top of a desk. Computer users typically find light in their peripheral fields to be too bright, causing glare and reflections on their screens. Minimize reflected glare on your screen by using window treatments, dimmer switches on lights and anti-glare screens. The light on a VDT screen and in an office should be balanced, which means dimmer lights are needed for screens with darker backgrounds. You can use a screen filter, shades or curtains to make the lighting more comfortable. You may need to turn off a light when using a computer. In general lighting levels of 200 to 700 lux (20 to 70 foot candles) are recommended for the workstation.

Stress Levels All people respond differently to computer work, depending on their visual needs, focusing abilities, amount of time spent on the computer and types of computers worked on. Research shows that symptomatic patients spent more time (roughly 6 hours per day) on the computer and worked longer on computers (roughly 8 years) than asymptomatic patients. Elderly people were most at risk for symptoms.

VDT displays with dark characters on a light background are easier on the eyes than light characters on a dark background. But either of these contrasts is more visible than green, yellow-orange, blue or red characters.

Flicking characters can also cause strain to the eyes. To reduce stress, take a break from the computer work every 20 minutes, meaning in non-computer tasks whenever possible. To avoid eye-focusing spasms, look away from the computer periodically.

Environmental Issues The electrostatic charge of VDT screens attract dust that can reduce visibility of the screen. Many office environments are dry. This can be a problem because the patient blinks less when viewing a VDT. More of his ocular surface is also exposed to the drying air when he looks at the VDT, as opposed to looking down at papers on the desk. These conditions can lead to dry eyes, especially in contact lens wearers.

Eye examination and dispensing appropriate spectacles:

During an eye exam we will be reviewing visual acuities, (how well you see at distance and near position), your focusing abilities, eye coordination. We will perform an internal health exam, with measuring of your intraocular pressure and a dry-eye work up, if necessary.

Some advice on selecting frames:

Select a good quality frame that will hold its adjustment. There are special bifocal spectacles made for computer use - please ask a dispenser or myself.
Proper fit across the bridge (nose) is necessary to ensure stability, adjustable nose pads help with minor adjustments.

Coatings and special materials added to spectacle lenses:

UV protection Although VDT produce only minor amounts of radiation, UV protection is an advisable feature to have in Saskatchewan.
Anti-reflection coatings enhance appearance by removing all detracting reflections and help greatly for night driving, computer usage, and those who work under florescent lighting.
Tints Some tints may help with contrast and resolution in the computer, but careful consideration must be given.
Scratch resistant coatings help eliminate visual disturbances at the computer due to significant scratches.

Other considerations:

For people requiring bifocals or a reading correction:

A new bifocal lens, exclusively for the computer user has been designed which gives a wider area of vision for close up with less head or eye movement. Ask one of the dispensers or myself if you are a consideration.
Single vision lens for close up work with the appropriate coatings.

Other testing procedures include:

Convergence insufficiency Your eyes do not turn into focus or swell as they should - sometimes eye exercises will help.
Accommodation Focusing problems for close up may involve special assistance.
Dry eye Wetting agents and dry eye treatment may be suggested to give comfort while working at a computer.

Please remember eye examinations done regularly with properly fitted eyewear can increase productivity and job satisfaction and remedy many symptoms brought on by computer usage. Should you have any questions please contact the office.

The information provided in this article and elsewhere on this website are for informational purposes only, and should NOT be considered a medical diagnosis or advice. When in doubt, please visit your local optometrist for a complete professional evaluation.