Understanding computer vision syndrome

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  • Understanding Computer Vision Syndrome

    Jon Torrey

    2003 Wiley Periodicals, Inc.Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ert.10073

    Computers have become a permanent partof our lives. Today, in virtually every cor-porate cubicle and backroom office, on thedesks of every secretary and executive, sits acomputer that allows us to write, design,compute, research, and communicate fasterthan we ever could before. Yet this conve-nience has not come without a price to ourhealth and general comfort level. Carpal tun-nel syndrome has become a universallyknown term. Not so widely known is com-puter vision syndrome, or CVS, which in factis far more widespread.

    There is no question that computers havemade our world smaller, allowed us torespond more quickly, put facts and figures atour fingertips, and made us more productive.Or have they? Are we unaware of some sim-ple steps that can ensure that we stay com-fortable and productive? Mounting evidenceshows that computer vision problems can sig-nificantly harm workplace productivity.

    Although computers have certainly madeour work lives easier and more efficient, theyplace an unusual strain on our physical well-being. The most widespread problem, CVS, ismarked by such symptoms as eyestrain;tired, burning eyes; headaches; blurredvision; neck and back pain; and musclespasms. The condition plays no favorites.Affected are computer users from all walksof lifeprogrammers, graphic artists, journal-ists, insurance adjusters, flight controllers,

    secretaries, teachers, editors, architects, andaccountants. It affects those who work at acomputer as much as ten hours a day andthose who spend as little as two hours a day.Although it my not be the hazard to life andlimb that unsafe conditions in the mines orthe factories were a century ago, its beencalled the number-one occupational hazardof the 21st century.

    Evidence of CVS is well documented. Con-sider these facts:

    The 2001 U.S. Census Report states thatmore than 143 million Americans spendtime at a computer every day, and that 54million of those are children. More than70 percent of these people are affected insome way by CVS (American OptometricAssociation, The Relationship of Com-puter Vision Syndrome and Musculoskele-tal Disorders, 1998).

    The U.S. Bureau of Labor Statisticsreported in 1998 that more than 75 mil-lion workers sit at computers every day.More than 70 percent of these people areaffected in some way by CVS.

    Nearly 88 percent of all computer userswill develop CVS at some time in theirlives (National Institute of OccupationalSafety and Health [NIOSH], Muscu-loskeletal Disorders Among VDT Work-ers: Individual, Ergonomic and the WorkOrganizational Factors, 1995).


  • Employment Relations Today

    Eyestrain is the number one complaint ofoffice workers. The more time you spendworking at a computer, the more likelyyou are to report problems with eyestrain(Cornell University, Computers in theSchools, 1999).

    Operating a VDT (video display terminal)may lead to visual, muscular, or mentalfatigue. Some people will need correctivelenses to avoid eyestrain and headaches(Occupational Safety and Health Adminis-tration [OSHA] Working Safely with VDTTerminals, 1996).


    How do computers cause CVS? Studies havelong shown that the computer screen is a verydifferent visual environment from the printedpage. Made up of tiny dots, or pixels, thecomputer screen is difficult for the eye tofocus on steadily. Poor definition of theseimages, compared with the clarity of a printedpage, causes the eyes to work harder. Thisforces our eye muscles to refocus continu-ously and subconsciously while we look atthe computer screen. This effort can amountto thousands of focusing cycles in a typicalworkday. Over time it creates the varioussymptoms known collectively as eyestrain. Itis similar to any musculoskeletal injury thatresults from overuse. One optometrist likensit to the eye doing hundreds, if not thousands,of pushups every day. Often, ergonomic chal-lenges compound the problem further, due tolimitations on placement of the monitor,increased susceptibility to glare, and poorselection of eyeglass lenses for computer use.

    Jon Torrey46

    Many computer users experience symp-toms of dry eyes, particularly people whowear contact lenses. Normally, when we reador do other close work, we hold the materialin our laps, as when we read a book or a mag-azine. Most of the surface of our eyes is cov-ered by our eyelids, so the tear film does notevaporate rapidly. Looking at a computer,however, typically means looking straightahead, not down. More of our eye surface isexposed, and the tear film can evaporate,causing a dry, burning, gritty sensation. Blinkrate can affect our comfort level, too. Accord-ing to a 1993 study in the New England Journalof Medicine, the blink rate in a relaxed state is22 blinks per minute, when reading printedmaterial, ten blinks per minute, and whenusing a computer, seven blinks per minute.When left untreated, vision problems canmove to other parts of the body and grow inseverity. An old adage is that the eyes leadthe body. This is certainly true when we usea computer. In order to see the screen clearly,computer users move their shoulders, heads,and necks, or hunch forward. Often, theydont realize their postures have deteriorateduntil they feel the muscular strain. Many peo-ple are familiar with the chicken-neck move-ment of those wearing bifocal lenses at thecomputerfirst they tip their heads back tosee through the reading segment, then theymove their heads forward to bring the screeninto focus. This results in tight, strained mus-cles in the shoulders and back. Often, thewrong symptoms are treated. If the eyes arenot treated, the back and shoulder pain willbecome progressively worse.

    Another cause of musculoskeletal problemscan be the type of lens design. Bifocals cancreate additional strain when using the com-puter, as previously described. This designoriginated in colonial times and provides clear

    When left untreated, vision problems can move to otherparts of the body and grow in severity.

  • Spring 2003

    vision only in the distance and up close forreading. Progressive lenses (also called no-linebifocals) are likewise not suitable for longperiods of computer use. They are excellentlenses for everyday tasks such as driving,walking, and reading. But the least effectivearea in a progressive lens is in the intermedi-ate area in the center of the lens, which isright where the wearers eyes will be lookingwhen using a computer. This is where thearea of clear vision becomes very narrow, asthe eyes move through the transition from dis-tance viewing to near viewing. The result canbe an excessive amount of head turning as theviewer looks from side to side while readingon screen, and additional strain from tippingthe head back to find the right power andkeep the screen clear. New lens designs,intended specifically for computer use, offermuch wider areas of clear vision and elimi-nate the constant head movement required byolder lens types.

    Health organizations such as NIOSH havelong viewed CVS as an occupational safetyissue and have called for more research in thisarea. However, more recently, studies haveshown that not only does CVS cause eye dis-comfort, but it also affects productivity in theworkplace. Evidence, in fact, shows that lowerproductivity is not limited to only the com-puter users who are symptomatic. A recentstudy clearly shows a performance decrease inworkers who report no CVS symptoms.


    Numerous clinical studies have documentedthe improvement in comfort, the reductionin symptoms, and the preference for eye-glasses containing the best possible pre-scription for computer viewing. But doesthe improvement in vision also make an

    Understanding Computer Vision Syndrome 47

    individual more productive? If so, does theimproved performance justify the expenseof providing the care?

    New data from recent studies show thatgood computer vision care easily pays foritself. Productivity studies were first con-ducted by the PRIO Corporation in the late1990s. PRIO, the leader in the growing com-puter vision-care market, developed and in1993 released the PRIO tester, an FDA-approved Class 1 medical device that allowseye doctors to accurately prescribe computer-specific eyewear for computer users. ThePRIO tester duplicates the poor edge defini-tion of typical computer pixels in a diagnos-tic instrument, inducing the same poorfocusing response a person experiences at acomputer. With this device, the eye doctor isable to determine the amount of correctionan individual needs to eliminate the ongoingfocusing effort, and allow his or her eyes torelax when at the computer. The companyalso markets a line of lenses and frames foruse at the computer.

    In 1998, PRIO initiated a comparativestudy with a national bank to see whetherproductivity or performance would beaffected with the intervention of PRIO-prescribed glasses in the work environment.The study parameters and conclusions wereas follows:

    A study population of 45 employees wasidentified within the banks largest creditcardprocessing facility as having symp-toms of eyestrain from computer use. Theseemployees were from several different

    New data from recent studies show that good computervision care easily pays for itself.

  • Employment Relations Today

    work groups, all spending significant timeeach day at a computer. The productivityof all employees at this facility is routinelymonitored on a variety of tasks, and thatinformation is used as part of their normalperformance evaluation.

    Members of this experimental group weregiven PRIO exams and eyeglasses withtheir PRIO-derived prescriptions for use atthe computer.

    A control group of the same size includedemployees from the same work groupswith similar levels of experience. Theseemployees did not receive exams orglasses, but their performance data wastracked and analyzed in the same manneras the experimental group.

    The bank performed its normal productiv-ity monitoring over an eight-week periodfor both groups.

    The control group showed an increase inproductivity of 6.1 percent over the eight-week period in terms of length of timerequired to locate information relative toa call being processed, number of callscompleted, etc.

    The PRIO group showed a productivityincrease of 15.7 percent over the sameperiod, exceeding the control groupsincrease by 9.6 percent.

    The PRIO groups improvement is signifi-cant. It amounts to approximately a 10:1return for the employer for an employee whocosts the company $30,000 per year in salaryand a total expense of $300 to provide an eyeexam and eyeglasses.

    Jon Torrey48


    Whenever human beings engage in a repetitiveactivity, particularly one as sedentary as com-puter use, the ergonomics of the workplaceneed to be addressed. Using a computer meanssitting in one position for long periods of time,exercising just a few sets of muscles. Whereasthe static parts of the body can get sore andstiff, the muscles being moved can getoverused. Fatigue and muscle or tendon sore-ness can result. In severe cases, computer usecan cause repetitive motion injuries (RMIs).

    Many companies have implemented veryeffective programs that identify and correctpotential physical problems before they occur.Articulated keyboards, wrist rests, and work-place exercises are frequently prescribed inorder to prevent carpal tunnel problems, forexample. Some companies expand this processto look at the effects on the vision system.Adding antiglare screens or moving workers tolarger monitors are steps often taken to reducethe specific vision complaints. Although thebenefits of good ergonomics programs are welldocumented elsewhere, the important ques-tion here is: How effective are these remediesat minimizing vision problems?

    A workplace study was conducted in 1999to answer these questions. It compared thereduction in visual symptoms from computer-specific eyewear with the reduction in symp-toms through ergonomic intervention. Thestudy, funded by PRIO, took place within thefacilities of a major telecommunicationsequipment manufacturer. The study identified22 employees within the company as havingCVS symptoms. These employees came fromseveral different work groups, all spendingsignificant time each day at a computer.

    Half of the workers had received a fullergonomic evaluation and optimization of

    Many companies have implemented very effective programsthat identify and correct potential physical problems beforethey occur.

  • Spring 2003

    their desks and workstations as part of theirnormal introduction and training, includingwhatever furniture or equipment changesthey needed. The other half of the subjectshad not received any ergonomic review orintervention. Both groups filled out a symp-tom questionnaire, identifying and detailingtheir visual symptoms over a one-weekperiod before receiving their computer eyeexams and computer glasses.

    Prior to receiving the eye exams andglasses, both groups reported the same levelof visual symptoms. The full ergonomic eval-uation and intervention had done nothing toreduce the vision symptoms, and these sub-jects experienced just as many symptoms asthe group that had not been given theergonomic evaluation.

    Both groups were given computer eye examsand glasses made up with their computer-specific prescriptions. After receiving theircomputer eyeglasses, the groups then contin-ued their normal job functions and filled outa symptom questionnaire once each week fora period of four weeks.

    Both groups reported a net decrease of 60percent in symptoms after four weeks ofwearing the computer-specific eyeglasses.Symptoms continued to decrease from thatpoint on, though at a slower rate. Both groupsequally experienced the reduction in symp-tom frequency and severity. The computervision care had produced improvements thatthe ergonomic intervention could not.


    A more extensive study was recently con-ducted by the University of Alabama at Birm-ingham (UAB) School of Optometry. Thestudy, funded by PRIO Corporation andVision Council of America, a national associa-

    Understanding Computer Vision Syndrome 49

    tion committed to furthering awareness ofvision care, examined the correlation betweenthe refractive corrections of workers usingcomputers and productivity in the workplace.

    The study has been submitted for publica-tion, but the preliminary results documentedthe following:

    There is a direct correlation between thecorrect prescription and productivity. Thisis particularly evident with more complexcomputer tasks such as data entry.

    There is a direct correlation between thetime the user takes to perform a task andthe correct prescription. The study taskstook much longer when the subjects werewearing less than the optimum correction.

    Computer users with moderately miscor-rected prescriptions may not be able totell the difference in their vision comfort,but t...