Computer Vision Syndrome: hours of screen time = eye strain

Infographic With Data on Computer Vision Syndrome

Graphic made available for sharing: CC BY-ND 3.0, by attribution. Infographic and story by K. Patricia Bouweraerts.

About 80 percent of adults in the U.S. view digital screens more than two hours each day, and close to 60 percent report symptoms of eye strain, according to The Vision Council.

Further, the American Optometric Association estimates the average worker is using a computer in the office or logging on remotely for as much as seven hours a day.

“Viewing a computer or digital screen often makes the eyes work harder,” the AOA posted. “As a result, the unique characteristics and high visual demands of computer and digital screen device viewing make many individuals susceptible to the development of vision-related symptoms. …Eyeglasses or contact lenses prescribed for general use may not be adequate for computer work.”

The AOA calls these symptoms digital eye strain, or Computer Vision Syndrome (CVS).

State University of New York College of Optometry researcher Mark Rosenfield found that Computer Vision Syndrome may significantly impact both visual comfort and occupational productivity, as 64 percent–90 percent of those who use digital screens experience effects such as eye strain, headaches, dry eye, double vision, or blurred vision after spending long sessions on the computer.

With such a large percentage of computer users experiencing visual symptoms, it follows that there would be a widespread awareness of options to manage digital eye strain. Yet, only 31 percent of Americans say they know about eyewear specifically designed to assist the eyes during digital device use, according to data from The Vision Council. Many more are unaware of the 20-20-20 rule, optimal settings for a monitor, or why Computer Vision Syndrome happens.

Infographic With Expanded Data on Computer Vision Syndrome

Graphic made available for sharing: CC BY-ND 3.0, by attribution. Infographic by K. Patricia Bouweraerts.

CVS symptoms include irritated eyes and blurred vision

Multiple sources describe the symptoms of Computer Vision Syndrome or digital eye strain as one or more of the following:

  • Eye strain
  • Headaches
  • Blurred vision
  • Dry eyes, burning and irritation
  • Neck and shoulder pain

Blurred distance vision may even persist after wrapping up a day’s screen-based work, the AOA posted.

If an eyeglass prescription is old or an individual needs glasses but hasn’t yet obtained an appropriate refraction,  CVS may become worse.

“Uncorrected vision problems can increase the severity of Computer Vision Syndrome or Digital Eye Strain symptoms,” according to the AOA. “…Even people who have an eyeglass or contact lens prescription may find it’s not suitable for the specific viewing distances of their computer screen. Some people tilt their heads at odd angles because their glasses aren’t designed for looking at a computer. Or they bend toward the screen in order to see it clearly. Their postures can result in muscle spasms or pain in the neck, shoulder or back.”

Why does CVS occur?

One of the primary root causes for Computer Vision Syndrome is that the human eye isn’t meant to maintain a fixed focus at the same intermediate distance for extended periods of time, according to multiple sources.

“Unlike printed text, each image or letter on a computer screen is made up of small pixels of light that are brightest in the center and become dimmer toward the edge of the pixel,” wrote Brent Motchan on EHSToday.com. “In addition, when viewing a computer screen, unconsciously the eyes repeatedly attempt to rest by shifting the focus of the eyes to a point somewhere beyond the screen. As a result, the eyes must constantly refocus back to the computer screen. This constant switch between screen and relaxation point creates eye strain and fatigue.”

Rosenfield’s study found that when primary gaze is on the computer for long stretches, individuals blink less often and sometimes only partially blink. This dries out the eyes, causing discomfort.

In fact, Christine Sindt, O.D. reported on the University of Iowa Hospitals & Clinics site that people blink 66 percent less during computer work, causing dryness and burning.

There is also the glare factor that applies to all screens, and flicker on CRT monitors. Windows and overhead lighting can reflect on digital screens, and monitors are sometimes set at lower than optimal refresh rates and resolution. Sindt wrote that a refresh rate of 70–85 Hz is better for the eyes.

Gary Heiting, O.D., agrees that a higher refresh rate is better, recommending a rate of 75 Hz or greater, and a high resolution screen with a dot pitch of .28 mm or smaller.

Strategies for managing digital eye strain

“Having a routine comprehensive eye exam every year is the most important thing you can do to prevent or treat computer vision problems,” according to The Vision Council. “During your exam, be sure to tell your eye doctor how often you use a computer and digital devices at work and at home.”

Optometrists and ophthalmologists can prescribe glasses or contacts specially refracted for intermediate viewing distances. They may offer additional strategies for relieving digital eye strain that are specific to an individual’s work requirements or lifestyle.

“Measure how far your eyes are from your screen when you sit at your computer, and bring this measurement to your exam so your eye doctor can test your eyes at that specific working distance,” Heiting added.

The AOA provides some general recommendations, such as taking a 15-minute break for every two hours of continuous work on the computer, and to follow the 20-20-20 rule. This rule is intended to be easy to remember — it consists of three steps, to look away from the screen every 20 minutes at an object about 20 feet away for 20 seconds.

In addition, the AOA advises that a screen be positioned 20–28 inches from the eyes, and about 4–5 inches below eye level as measured from the center of the monitor.

Other techniques to try involve adjusting screen brightness and text size.

“You want your monitor’s brightness to match your surrounding workspace brightness,” wrote Roberto Baldwin and Josie Colt on Wired.com. “To achieve this, look at the white background of this page. If it looks like a light source in the room, it’s too bright. If it seems dull and gray, it’s probably too dark.”

In addition, it may be helpful to reduce glare from strong sunlight shining through windows and from fluorescent or overhead lamps, according to several sources. Further, text can be viewed larger on many operating systems by clicking Control+ (PC) or Command+ (Mac) in the browser, or through the View menu of many software programs. A larger monitor may be another option.

“A good rule of thumb: text should be three times the smallest size you can read from a normal viewing position,” Baldwin and Colt added. “When it comes to color combinations, your eyes prefer black text on a white or slightly yellow background.”

Also, remember to blink — and blink fully — when using digital screens. This will moisten the eyes and keep them fresher between rest breaks.

“As modern society continues to move towards greater use of electronic devices for both work and leisure activities, it seems likely that the visual demands that these place upon our patients will only continue to increase,” Rosenfield wrote.

 

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