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Page 1: VIRTUAL- REALITY THERAPY - University of Washingtonhitl.washington.edu/projects/vrpain/index_files/SCIAMFin.pdf · the use of virtual reality as a tool for pain control. In other

VIRTUAL-REALITYTHERAPY

BURN PATIENT participates in a virtual-reality program to relieve the pain of his wound care at Harborview Burn Center in Seattle (above). Wearing a headset and manipulating a joystick, the patient maneuvers through the program calledSnowWorld (right), which was specifically designed to ease the pain of burn victims. Studies show that virtual-reality programsare more effective than ordinary video games in distracting patients from the often excruciating pain of wound care.

Patients can get relief from pain or overcome their phobias by immersing themselves incomputer-generated worlds BY HUNTER G. HOFFMAN

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COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

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For the past several years, I haveworked with David R. Patterson, a painexpert at the University of WashingtonSchool of Medicine, to determine whetherseverely burned patients, who often faceunbearable pain, can relieve their dis-comfort by engaging in a virtual-realityprogram during wound treatment. Theresults have been so promising that a fewhospitals are now preparing to explorethe use of virtual reality as a tool for paincontrol. In other projects, my colleaguesand I are using virtual-reality applicationsto help phobic patients overcome their ir-rational fear of spiders and to treat post-traumatic stress disorder (PTSD) in sur-vivors of terrorist attacks.

At least two software companies arealready leasing virtual-reality programsand equipment to psychologists for pho-bia treatment in their offices. And the Vir-

tual Reality Medical Center, a chain ofclinics in California, has used similar pro-grams to successfully treat more than 300patients suffering from phobias and anx-iety disorders. Although researchers mustconduct more studies to gauge the effec-tiveness of these applications, it seemsclear that virtual therapy offers some veryreal benefits.

SpiderWorld and SnowWorldFEW EXPERIENCES are more intensethan the pain associated with severe burninjuries. After surviving the initial trauma,burn patients must endure a long journeyof healing that is often as painful as theoriginal injury itself. Daily wound care—

the gentle cleaning and removal of deadtissue to prevent infection—can be so ex-cruciating that even the aggressive use ofopioids (morphine-related analgesics)

cannot control the pain.The patient’s healing

skin must be stretched topreserve its elasticity, to re-

duce muscle atrophy and toprevent the need for further

skin grafts. At these times,most patients—and especially

children—would love to trans-port their minds somewhere else

while doctors and nurses treattheir wounds. Working with the

staff at Harborview Burn Center inSeattle, Patterson and I set out in

1996 to determine whether immersivevirtual-reality techniques could be used

to distract patients from their pain. Theteam members include Sam R. Sharar,Mark Jensen and Rob Sweet of the Uni-versity of Washington School of Medi-cine, Gretchen J. Carrougher of Har-borview Burn Center and Thomas Fur-ness of the University of WashingtonHuman Interface Technology Laborato-ry (HITLab).

Pain has a strong psychological com-ponent. The same incoming pain signalcan be interpreted as more or less painfuldepending on what the patient is think-ing. In addition to influencing the way pa-tients interpret such signals, psychologi-cal factors can even influence the amountof pain signals allowed to enter the brain’scortex. Neurophysiologists Ronald Mel-zack and Patrick D. Wall developed this“gate control” theory of pain in the 1960s[see “The Tragedy of Needless Pain,” byRonald Melzack; Scientific American,February 1990].

Introducing a distraction—for exam-ple, by having the patient listen to music—

has long been known to help reduce painfor some people. Because virtual reality isa uniquely effective new form of distrac-tion, it makes an ideal candidate for paincontrol. To test this notion, we studiedtwo teenage boys who had suffered gaso-line burns. The first patient had a severeburn on his leg; the second had deep burnscovering one third of his body, includinghis face, neck, back, arms, hands and legs.Both had received skin-graft surgery andstaples to hold the grafts in place.

We performed the study during the re-moval of the staples from the skin grafts.

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■ One of the best ways to alleviate pain is to introduce a distraction. Becausevirtual reality immerses users in a three-dimensional computer-generatedworld, it is uniquely suited to distracting patients from their pain.

■ Burn patients undergoing wound care report that their pain drops dramaticallywhen they engage in virtual-reality programs. Functional magnetic resonanceimaging shows that virtual reality actually reduces the amount of pain-relatedactivity in the brain.

■ Virtual-reality programs can also help phobic patients overcome their fear of spiders, heights, flying or public speaking. A specially designed program is now being used to treat post-traumatic stress disorder in survivors of the September 11 attacks.

Overview/Virtual-Reality Therapy

In the science-fiction thriller The Matrix, the heroes “plugged in”

to a virtual world. While their bodies rested in reclining chairs,

their minds fought martial-arts battles, dodged bullets and

drove motorcycles in an elaborately constructed software

program. This cardinal virtue of virtual reality—the ability

to give users the sense that they are “somewhere else”—can

be of great value in a medical setting. Researchers are find-

ing that some of the best applications of the software focus

on therapy rather than entertainment. In essence, virtual

reality can ease pain, both physical and psychological.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

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The boys received their usual opioid med-ication before treatment. In addition,each teenager spent part of the treatmentsession immersed in a virtual-reality pro-gram and an equal amount of time play-ing a popular Nintendo video game (ei-ther Wave Race 64, a jet-ski racing game,or Mario Kart 64, a race-car game). Thevirtual-reality program, called Spider-World, had originally been developed asa tool to overcome spider phobias; weused it for this investigation because it

was the most distracting program avail-able at the time and because we knew itwould not induce nausea. Wearing astereoscopic, position-tracked headsetthat presented three-dimensional comput-er graphics, the patients experienced theillusion of wandering through a kitchen,complete with countertops, a windowand cabinets that could be opened. An im-age of a tarantula was set inside the vir-tual kitchen; the illusion was enhanced bysuspending a furry spider toy with wiggly

legs above the patient’s bed so that hecould actually feel the virtual spider.

Both teenagers reported severe to ex-cruciating pain while they were playingthe Nintendo games but noted largedrops in pain while immersed in Spider-World. (They rated the pain on a zero to100 scale immediately after each treat-ment session.) Although Nintendo canhold a healthy player’s attention for along time, the illusion of going inside thetwo-dimensional video game was found

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PAIN-RELATED BRAIN ACTIVITY

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When healthy volunteers receivedpain stimuli, functional magneticresonance imaging showed largeincreases in activity in severalregions of the brain that are knownto be involved in the perception ofpain (near right and below). Butwhen the volunteers engaged in avirtual-reality program during thestimuli, the pain-related activitysubsided (far right and bottom).

CHANGES IN BRAINACTIVITY IN

RESPONSE TO PAINGreatestincrease

Some increase

Some decrease

Greatestdecrease

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to be much weaker than the illusion of go-ing into virtual reality. A follow-up studyinvolving 12 patients at Harborview BurnCenter confirmed the results: patients us-ing traditional pain control (opioidsalone) said the pain was more than twiceas severe compared with when they wereinside SpiderWorld.

Why is virtual reality so effective in al-leviating pain? Human attention has beenlikened to a spotlight, allowing us to selectsome information to process and to ignoreeverything else, because there is a limit tohow many sources of information we canhandle at one time. While a patient is en-gaged in a virtual-reality program, thespotlight of his or her attention is nolonger focused on the wound and the painbut drawn into the virtual world. Becauseless attention is available to process in-coming pain signals, patients often expe-rience dramatic drops in how much painthey feel and spend much less time think-ing about their pain during wound care.

To increase the effec-tiveness of the virtual ther-

apy, our team created Snow-World, a program specifical-

ly customized for use withburn patients during wound

care. Developed with fundingfrom Microsoft co-founder Paul

G. Allen and the National Insti-tutes of Health, SnowWorld pro-

duces the illusion of flying throughan icy canyon with a frigid river and

waterfall, as snowflakes drift down[see illustration on pages 58 and 59].

Because patients often report that theyare reliving their original burn experienceduring wound care, we designed a glaciallandscape to help put out the fire. As pa-tients glide through the virtual canyon,they can shoot snowballs at snowmen,igloos, robots and penguins standing onnarrow ice shelves or floating in the riv-er. When hit by a snowball, the snowmenand igloos disappear in a puff of powder,the penguins flip upside down with aquack, and the robots collapse into aheap of metal.

More recent research has shown thatthe benefits of virtual-reality therapy arenot limited to burn patients. We con-ducted a study involving 22 healthy vol-unteers, each of whom had a blood pres-sure cuff tightly wrapped around one armfor 10 minutes. Every two minutes thesubjects rated the pain from the cuff; asexpected, the discomfort rose as the ses-sion wore on. But during the last two min-utes, each of the subjects participated intwo brief virtual-reality programs, Spi-

derWorld and ChocolateWorld. (In Choc-olateWorld, users see a virtual chocolatebar that is linked through a position sen-sor to an actual candy bar; as you eat thereal chocolate bar, bite marks appear onthe virtual bar as well.) The subjects re-ported that their pain dropped dramati-cally during the virtual-reality session.

What is more, improving the qualityof the virtual-reality system increases theamount of pain reduction. In anotherstudy, 39 healthy volunteers received athermal pain stimulus—delivered by anelectrically heated element applied to theright foot, at a preapproved temperatureindividually tailored to each participant—for 30 seconds. During this stimulus, 20of the subjects experienced the fully in-teractive version of SnowWorld with ahigh-quality headset, sound effects andhead tracking. The other 19 subjects sawa stripped-down program with a low-quality, see-through helmet, no sound ef-fects, no head tracking and no ability toshoot snowballs. We found a significantpositive correlation between the potencyof the illusion—how strongly the subjectsfelt they were immersed in the virtualworld—and the alleviation of their pain.

Seeing Pain in the BrainOF COURSE, all these studies relied onthe subjective evaluation of the pain by thepatients. As a stricter test of whether vir-tual reality reduces pain, I set out with mycolleagues at the University of Washing-ton—including Todd L. Richards, Aric R.Bills, Barbara A. Coda and Sam Sharar—

to measure pain-related brain activity us-

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VIRTUAL-REALITY PROGRAM re-creating a bus bombing is designed totreat post-traumatic stress disorder in survivors of terrorist attacks inIsrael and Spain. By gradually exposing the survivors to realistic images

and sounds of a bus bombing (three screen shots are shown here), theprogram helps them to process and eventually reduce the debilitatingemotions associated with the traumatic event.

Virtual reality is not just

changing the way patients

interpret incoming

pain signals; the programs

actually reduce the

amount of pain-related

brain activity.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

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ing functional magnetic resonance imag-ing (fMRI). Healthy volunteers underwenta brain scan while receiving brief painstimulation through an electrically heatedelement applied to the foot. When the vol-unteers received the thermal stimuli with-out the distraction of virtual reality, theyreported severe pain intensity and un-pleasantness and spent most of the timethinking about their pain. And, as expect-ed, their fMRI scans showed a large in-crease in pain-related activity in five re-gions of the brain that are known to be in-volved in the perception of pain: theinsula, the thalamus, the primary and sec-ondary somatosensory cortex, and the af-fective division of the anterior cingulatecortex [see illustration on page 61].

Creating virtual-reality goggles thatcould be placed inside the fMRI machinewas a challenge. We had to develop afiber-optic headset constructed of non-ferrous, nonconducting materials thatwould not be affected by the powerfulmagnetic fields inside the fMRI tube. Butthe payoff was gratifying: we found thatwhen the volunteers engaged in Snow-World during the thermal stimuli, thepain-related activity in their brains de-creased significantly (and they also re-ported large reductions in subjective painratings). The fMRI results suggest thatvirtual reality is not just changing theway patients interpret incoming pain sig-nals; the programs actually reduce theamount of pain-related brain activity.

Encouraged by our results, two largeregional burn centers—the William Ran-dolph Hearst Burn Center at New YorkWeill Cornell Medical Center andShriners Hospital for Children in Galves-ton, Tex.—are both making preparationsto explore the use of SnowWorld for paincontrol during wound care for severeburns. Furthermore, the Hearst Burn Cen-ter, directed by Roger W. Yurt, is helpingto fund the development of a new upgrade,

SuperSnowWorld, which will feature life-like human avatars that will interact withthe patient. SuperSnowWorld will allowtwo people to enter the same virtualworld; for example, a burn patient and hismother would be able to see each other’savatars and work together to defeat mon-strous virtual insects and animated seacreatures rising from the icy river. By max-imizing the illusion and interactivity, theprogram will help patients focus their at-tention on the virtual world during par-ticularly long and painful wound care ses-sions. Now being built by Ari Hollander,an affiliate of HITLab, SuperSnowWorldwill be offered to medical centers free ofcharge by the Hearst and Harborviewburn centers.

Virtual-reality analgesia also has thepotential to reduce patient discomfortduring other medical procedures. BruceThomas and Emily Steele of the Universi-ty of South Australia have found that vir-

tual reality can alleviate pain in cerebralpalsy patients during physical therapy af-ter muscle and tendon surgery. (Aimed atimproving the patient’s ability to walk,this therapy involves exercises to stretchand strengthen the leg muscles.) Our teamat the University of Washington is ex-ploring the clinical use of virtual realityduring a painful urological procedurecalled a rigid cystoscopy. And we haveconducted a study showing that virtualreality can even relieve the pain and fearof dental work.

Fighting FearA N O T H E R T H E R A P E U T I C applica-tion of virtual reality is combating pho-bias by exposing patients to graphic sim-ulations of their greatest fears. This formof therapy was introduced in the 1990sby Barbara O. Rothbaum of Emory Uni-versity and Larry F. Hodges, now at theUniversity of North Carolina at Char-lotte, for treating fear of heights, fear offlying in airplanes, fear of public speak-ing, and chronic post-traumatic stressdisorder in Vietnam War veterans. Likethe pain-control programs, exposuretherapy helps to change the way peoplethink, behave and interpret information.

Working with Albert Carlin of HIT-

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HUNTER G. HOFFMAN is director of the Virtual Reality Analgesia Research Center at the Uni-versity of Washington Human Interface Technology Laboratory (HITLab) in Seattle. He isalso an affiliate faculty member in the departments of radiology and psychology at the Uni-versity of Washington School of Medicine. He joined the HITLab in 1993 after earning hisPh.D. in cognitive psychology at the University of Washington. To maximize the effective-ness of virtual reality in reducing physical and psychological suffering, he is exploring waysto enhance the illusion of going inside a computer-generated virtual world.

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FEAR OF PUBLIC SPEAKING can be treated using a virtual-reality program developed byVirtually Better, a software company based in Decatur, Ga., that leases its programs topsychologists and psychiatrists. Ken Graap, the company’s chief executive, practices a speech in front of a virtual audience, shown on his headset and on the computer monitor.

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Lab and Azucena Garcia-Palacios ofJaume I University in Spain (a HITLab af-filiate), our team has shown that virtual-reality exposure therapy is very effectivefor reducing spider phobia. Our first spi-der-phobia patient, nicknamed MissMuffet, had suffered from this anxiety dis-order for nearly 20 years and had acquireda number of obsessive-compulsive behav-iors. She routinely fumigated her car withsmoke and pesticides to get rid of spiders.Every night she sealed all her bedroomwindows with duct tape after scanning theroom for spiders. She searched for thearachnids wherever she went and avoidedwalkways where she might find one. Af-ter washing her clothes, she immediatelysealed them inside a plastic bag to makesure they remained free of spiders. Overthe years her condition grew worse.When her fear made her hesitant to leavehome, she finally sought therapy.

Like other kinds of exposure therapy,the virtual-reality treatment involves in-troducing the phobic person to the feared

object or situation a little at a time. Bit bybit the fear decreases, and the patient be-comes more comfortable. In our first ses-sions, the patient sees a virtual tarantulain a virtual kitchen and approaches asclose as possible to the arachnid while us-ing a handheld joystick to navigatethrough the three-dimensional scene. Thegoal is to come within arm’s reach of thevirtual spider.

During the following sessions, theparticipant wears a glove that tracks theposition of his or her hand, enabling thesoftware to create an image of a hand—

the cyberhand—that can move throughthe virtual kitchen. The patient maneu-vers the cyberhand to touch the virtualspider, which is programmed to respondby making a brief noise and fleeing a fewinches. The patient then picks up a virtu-al vase with the cyberhand; when the pa-tient lets go, the vase remains in midair,but an animated spider with wiggling legscomes out. The spider drifts to the floorof the virtual kitchen, accompanied by a

brief sound effect from the classic horrormovie Psycho. Participants repeat eachtask until they report little anxiety. Thenthey move on to the next challenge. Thefinal therapy sessions add tactile feed-back to the virtual experience: a toy spi-der with an electromagnetic position sen-sor is suspended in front of the patient,allowing him or her to feel the furry ob-ject while touching the virtual spider withthe cyberhand.

After only 10 one-hour sessions, MissMuffet’s fear of spiders was greatly re-duced, and her obsessive-compulsive be-haviors also went away. Her success wasunusually dramatic: after treatment, shewas able to hold a live tarantula (whichcrawled partway up her arm) for severalminutes with little anxiety. In a subse-quent controlled study of 23 patients di-agnosed with clinical phobia, 83 percentreported a significant decrease in theirfear of spiders. Before treatment, thesepatients could not go within 10 feet of acaged tarantula without high anxiety; af-

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SPIDERWORLD is a virtual-reality program designed to help phobicpatients overcome their fear of spiders. The patient wears a headsetthat shows a virtual tarantula (screen shot from program is shown in

background). To provide tactile feedback, the system tracks thepositions of a toy spider (suspended by the author, at left) and thepatient’s hand, allowing her to “touch” the virtual creature.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

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ter the virtual-reality therapy, most ofthem could walk right up to the cage andtouch its lid with only moderate anxiety.Some patients could even remove the lid.

Similar programs can be incorporat-ed into the treatment of a more seriouspsychological problem: post-traumaticstress disorder. The symptoms of PTSDinclude flashbacks of a traumatic event,intense reactions to anything symbolizingor resembling the event, avoidance be-haviors, emotional numbing, and irri-tability. It is a debilitating disorder that af-fects the patient’s social life and job per-formance and is much more challengingto treat than specific phobias. Cognitivebehavioral therapy protocols, such as theprolonged exposure therapy developedby University of Pennsylvania psycholo-gist Edna Foa, have a high success rate forpatients with PTSD. The exposure thera-py is thought to work by helping patientsprocess and eventually reduce the emo-tions associated with the memories of thetraumatic event. The therapist graduallyexposes the patient to stimuli that activatethese emotions and teaches the patienthow to manage the unwanted responses.

Researchers are now exploring wheth-er virtual-reality programs can be used tostandardize the therapy and improve theoutcome for patients, especially thosewho do not respond to traditional meth-ods. JoAnn Difede of Cornell Universityand I developed a virtual-reality exposuretherapy to treat a young woman who wasat the World Trade Center during theSeptember 11 attacks and later developedPTSD. During the therapy, the patient puton a virtual-reality helmet that showedvirtual jets flying over the towers andcrashing into them with animated explo-sions and sound effects. Although theprogress of the therapy was gradual andsystematic, the scenes presented by thesoftware in the final sessions were grue-somely realistic, with images of peoplejumping from the burning buildings andthe sounds of sirens and screams. Thesestimuli can help patients retrieve memo-ries of the event and, with the guidance ofa therapist, lower the discomfort of re-membering what happened.

Our first patient showed a large andstable reduction in her PTSD symptoms

and depression after the vir-tual-reality sessions. Otherpatients traumatized by thetower attacks are now beingtreated with virtual-reality ther-apy at Weill Cornell MedicalCollege and New York Presbyter-ian Hospital. I am also collaborat-ing with a team of researchers led byPatrice L. (Tamar) Weiss of HaifaUniversity in Israel and Garcia-Pala-cios to create a virtual-reality treatmentfor survivors of terrorist bombings whodevelop PTSD.

Virtual Reality by the HourBECAUSE DOZENS of studies have es-tablished the efficacy of virtual-realitytherapy for treating specific phobias, thisis one of the first medical applications tomake the leap to widespread clinical use.Virtually Better, a Decatur, Ga.–basedcompany that was co-founded by virtual-reality pioneers Hodges and Rothbaum,has produced programs designed to treatan array of anxiety disorders, includingfear of heights, fear of flying and fear ofpublic speaking. The company is leasing itssoftware to psychologists and psychiatristsfor $400 a month, allowing therapists toadminister the treatments in their own of-fices. A Spanish firm called PREVI offerssimilar programs. Instead of reclining ona couch, patients interactively confronttheir fears by riding in virtual airplanes orby standing in front of virtual audiences.

In contrast, more research is neededto determine whether virtual reality canenhance the treatment of PTSD. Scien-tists have not yet completed any ran-domized, controlled studies testing the ef-fectiveness of virtual-reality therapy fortreating the disorder. But some of theleading PTSD experts are beginning toexplore the virtues of the technology, andthe preliminary results are encouraging.

Large clinical trials are also needed to

determine the value of virtual-reality anal-gesia for burn patients. So far the researchhas shown that the SnowWorld programposes little risk and few side effects. Be-cause the patients use SnowWorld in ad-dition to traditional opioid medication,the subjects who see no benefit from vir-tual reality are essentially no worse offthan if they did not try it. Virtual realitymay eventually help to reduce reliance onopioids and allow more aggressive woundcare and physical therapy, which wouldspeed up recovery and cut medical costs.The high-quality virtual-reality systemsthat we recommend for treating extremepain are very expensive, but we are opti-mistic that breakthroughs in display tech-nologies over the next few years will low-er the cost of the headsets. Furthermore,patients undergoing less painful proce-dures, such as dental work, can use cheap-er, commercially available systems. (Pho-bia patients can also use the less expensiveheadsets.)

The illusions produced by these pro-grams are nowhere near as sophisticatedas the world portrayed in the Matrixfilms. Yet virtual reality has maturedenough so that it can be used to help peo-ple control their pain and overcome theirfears and traumatic memories. And asthe technology continues to advance, wecan expect even more remarkable appli-cations in the years to come.

w w w . s c i a m . c o m S C I E N T I F I C A M E R I C A N 65

Virtual Reality Exposure Therapy for World Trade Center Post-Traumatic Stress Disorder: A Case Report. JoAnn Difede and Hunter G. Hoffman in CyberPsychology & Behavior, Vol. 5, No. 6,pages 529–535; 2002. Available at www.hitl.washington.edu/people/hunter/wtc.pdf

Virtual Reality Technology. Second edition, with CD-ROM. Grigore C. Burdea and Philippe Coiffet.John Wiley & Sons, 2003.

More information about virtual-reality therapy can be found on the Web at www.hitl.washington.edu/and www.e-therapy.info

M O R E T O E X P L O R E

Another therapeutic

application of virtual reality

is combating phobias by

exposing patients to

graphic simulations

of their greatest fears.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.