外报阅读18.docx
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外报阅读18.docx
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外报阅读18
文登考研英语钻石卡(VIP)外报阅读第18期
Passage1:
Contactlenses
Lookintomyeyes
Biotechnology:
Smartcontactlensesexploittheunusualcharacteristicsoftheeyetodiagnosedisease,deliverdrugsandmorebesides
Jun2nd2011|fromtheprintedition
EYEScanrevealanawfullotaboutsomebody.Lookintosomeone’seyesandyoucantellifheishappyorsad,truthfulorinsincere,soberordrunk.Bypeeringdeeperstill,ophthalmologistsareevenabletogaugeaperson’shealth,spottingfarmorethanjustconditionsthataffecttheeyeitself:
hypertensionandbraintumourscanalsobediagnosedbyexaminingtheretina.Eyesareinmanyrespectswindowsonthebody,eveniftheyarenotquitewindowsonthesoul.
Andnowcontactlenses,normallyusedtobringtheoutsideworldintofocus,aremakingitpossibletopeerbackinthroughthesewindows.Theideaof“smart”contactlensesthatcansuperimposeinformationonthewearer’sfieldofviewhasbeenaroundforawhile,butcontactlensesarealsobeingdevelopedthatuseembeddedsensorsandelectronicstomonitordiseaseanddispensedrugs.Suchdevicesmayeventuallybeabletomeasurethelevelofcholesteroloralcoholinyourbloodandflashupanappropriatewarning.
Thetechnologyhashugepotential,saysBabakParviz,aresearcherattheUniversityofWashington,inSeattle,whoisoneofthepioneersofsmartcontactlenses.Suchlensescouldactasbothsensorsanddisplays,providingnewwaysfordatatopassinandoutofthebody.Byaddingtinylight-emittingelementstocontactlenses,itisbecomingpossibletomapdigitalimagesdirectlyontothewearer’sfieldofvisiontocreateahead-updisplayoraugmented-realityoverlaythatrequiresnoglasses,screenorheadset.“Theultimategoalwouldbetohaveafullyfledgeddisplay,”saysDrParviz.
Thefirstsmartcontactlensesarealreadyonthemarket.TheTriggerfish,createdbySensimed,aspin-offfromtheSwissFederalInstituteofTechnologyinLausanne,isawirelesslypoweredcontactlensdesignedtohelppeoplewithglaucomamanagetheirtreatment.Itdoesthisbycontinuouslymeasuringthecurvatureoftheeyeovera24-hourperiodusingatinystraingauge,builtusingmicro-electromechanicalsystem(MEMS)technology,whichisincorporatedintothelens.
Inpatientswithglaucoma,fluidbuildsupwithintheeyeandputspressureontheopticnerve.Ifitisn’ttreatedcorrectlythiscanirreversiblydamagethepatient’svision,saysJean-MarcWismer,Sensimed’schiefexecutive.Butdeterminingthecorrectdrugtreatmentdependsuponfirstknowingwhenduringthedaytheintraocularpressure(IOP)peaks.
Theprofileofthispressureisbelievedtofollowcharacteristiccircadianpatterns.Butatthemomentthereisnotechnologythatcanmeasureitcontinuously.“Thestandardtodayistoplacepatientsinalaboratoryfor24hours,”saysMrWismer.Duringthistimeapatient’sIOPcanbemeasuredeveryfewhoursusingastandardmachinecalledaGoldmanntonometer.ButalthoughthisapproachcanmeasuretheIOPveryeffectively,itisunabletodosocontinuously.
Aneyeforaneye
Bymeasuringthechangesinthecurvatureoftheeyecausedbyabuild-upofinternalpressure,Sensimed’sTriggerfishlenscanbuildupamuchmoreaccurateprofile.Inadditiontothestraingauge,alltheelectronicsrequiredtohandlethesignal-processingandcommunicationsareembeddedwithinthesiliconelens(pictured).
Aninductionloopisusedtopowerthedeviceandtorelaydatafromthelenstoareceiverwornbythepatient.(Inductionloopsarealsousedtopowerhearing-aidimplantswithouttheneedfortroublesomewires.)Sincetheendof2010thetechnologyhasbeenavailableineightEuropeancountries,andapprovalinAmericaisexpectedbytheendofthisyear,accordingtoMrWismer.“Wecurrentlyhaveabout200patientsintotal,”hesays.
Tearscontainchargedatomswhichinterferewiththeoperationofasmartlens’sbuilt-inantenna
Thedevicedoeshaveonesignificantdrawback,however.Theshortrangeoftheinduction-loopantennainthelensmeanstheexternalantennahastobeveryclosetotheeye:
tapedaroundtheeyesocket,infact.Wearingasmallchipinyoureye(normalvisionisnotimpaired)looksstrangeenough,buthavingagiantmonocletapedtoyourheadlooksstrangerstill.
Itislessthanideal,MrWismeradmits,buthisfirm’sdeviceisnotmeanttobeworncontinuously.Instead,theideaisthatitwouldbewornfor24hoursonceeverysixmonthsorso.ThehopeisthatthisdevicewillhelptoimprovethetreatmentofglaucomabyilluminatingtherelationshipbetweenvariationsintheIOPandtheprogressionofthedisease.
Anothersmartcontactlensis,however,designedtobeworncontinuously.Althoughstillunderdevelopment,thislensisaimedattreatingdiseasesratherthanmonitoringthem.IthasbeendevelopedbyDanielKohane,aprofessorofanaesthesiologyanddirectoroftheLaboratoryforBiomaterialsandDrugDeliveryattheChildren’sHospitalinBoston.Hissmartlensesaredesignedtoreleasedrugsslowlyintotheeyeoveralongperiod.
Comparedwiththesimplicityofeyedropsthismayseemabitoverthetop,butthereareverygoodreasonstodevelopthissortoftechnology,saysDrKohane.“Eyedropsarenotveryefficient—onlyasmallfractionactuallygetsintotheeye,”hesays.“Butthebiggerproblemiscompliance.”Acommonproblemwithophthalmicdiseasesisthatpatientsfailtoapplytheireyedropsasprescribed.“Thingsthatshouldworkdon’twork,andthatleadstoanescalationofthediseaseandthetherapy.”
Anewperspectiveondrugdelivery
DrKohane’ssolutionistocreateatypeofcontactlensesthathasencapsulatedwithinitapouchcontainingadrug.“It’saflattoroidordoughnutmadeoutofapermeablepolymerthatcontainsthedrug,”hesays.“Asthefilmdegradesitreleasesthedrug,leachingoutslowly.”Thepayloadcouldbealmostanything,suchasapainkiller,anantibioticorananti-inflammatorydrug.Invitroexperimentshaveshowedthatsuchalenscouldcontinuetoreleaseciprofloxacin,anantibiotic,inacontrolledmannerformorethan100days.
Thecurrentdesignispurelypassive,butDrKohaneisnowworkingonaversionthatcanbetriggeredinresponsetoaparticularstimulus.IfhislensweretobecombinedwithsensorslikethosefoundintheTriggerfish,forexample,itwouldbepossibletomonitortheIOPanddeliverglaucomadrugswhenitpeaks.Butthereareotherthingsthathavetobetakenintoaccount.“IfIcough,myIOPgoesup,”saysDrKohane.Asmartcontactlenswouldhavetobecleverenoughtocopewiththis.
Anadditionalconcernistheeffecthistherapeuticlensmayhaveonthewearer’svision.“Aconcernisthatasthedrugisreleased,thechangeinshapewillalterthefocusofthepatient,”saysDrKohane.Thisisonereasonwhythepouchisdoughnut-shaped,sothatitwrapsaroundthepupilwithoutobscuringthewearer’svision.“Asfaraswecantellthatdoesn’tchangeitmuch,”hesays.
Smartcontactlensesdon’tjusthavetofocusonmonitoringortreatingtheeyes.DrParvizhasbeendevelopingadifferenttypeoflensintendedformonitoringglucoselevelsinpeoplewithdiabetes.Theeyeisasurprisinglygoodplacetodothisnon-invasively,becauseglucoselevelsintearfluidcorresponddirectlytothoseintheblood,hesays.Thismeanslevelscanbecontinuouslygaugedwithoutsomuchasapinprick.
TomeasuretheglucoselevelDrParvizusesatechniquecalledamperometricsensingthatinvolvesmeasuringthechangesintinycurrentsbetweensetsofelectrodes.LiketheTriggerfish,thelensispoweredandcommunicateswirelessly.Buthisdesignhasagreaterrange,sonoinductionlooparoundtheeyeisneeded.
Testsonrabbitshaveshowedthatthelensesworkandcandetectevenverylowglucoselevels,saysDrParviz.Butthereisaproblemwithusingamperometricsensing:
theelectrodesarenotsealedwithinthelens,andthereforeareexposed.Proteinsthenbuilduponthesensors,affectingtheiroperationandreducingtheusefullifespanofthelens.Itispossiblethatcleaningthelensregularlycouldreducethisproblem,butitisunclearwhateffectlens-cleaningfluidwouldhaveonitsbuilt-inelectronics.Tearsalsoposeaproblem,becausetheycontainelectricallychargedatoms,orions,whichinterferewiththeoperationofthesmartlens’sbuilt-inantenna.
AswithSensimed’sdevice,alltheelectronicsandsensorsinDrParviz’scontactlensarelocatedoutsidethecentralareaofthelens,toavoidinterferencewiththewearer’svision.ButDrParvizwantstoadddisplayelements,intheformoftinyembeddedlight-emittingdiodes(LEDs),tohislensessothattheycanoverlayinformationonthewearer’sfieldofview.
DrParvizhasalreadydemonstratedthatredandbluedots,orpixels,canindeedbeembeddedinlenses,thoughgreenwillalsoberequiredtocreateafull-colourdisplay.Hehasshownthatthepixelscanbepoweredwirelesslyandhehasdemonstratedthathecanshrinktheopticsrequiredtobringthesedotsoflightintofocus,evenwhentheyaresoclosetotheeye.Sofar,however,theclosestDrParvizhascometocreatinganactualdisplayisalenscontainingagridofjusteightpixels.
Giventheubiquityofhigh-definitionscreenscontainingmillionsofpixelsthismaynotseemveryimpressive.Butitisworthrememberingthatthisismuchmoredifficultthancreatingnormaldisplays.Quiteapartfromthechallengesofpoweringsuchasmalldeviceandbringingthepixelsintofocus,thesmallsizeofacontactlensmeansthatthepixelswillhavetobemuchsmallerthanthoseinatypicalcomputermonitorormobile-phonedisplayinordertoprovideasimilarresolution.
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