2023学年完整公开课版BOOK7-Unit1Livingwell【全国一等奖】

Blindness

BlindnessClassificationsandexternalresources

TheBlindGirl(1856),apaintingbyJohnEverettMillais

Blindnessistheconditionoflackingvisualperceptionduetophysiologicalorpsychologicalfactors.

Variousscaleshavebeendevelopedtodescribetheextentofvisionlossanddefine"blindness".Totalblindnessisthecompletelackofformandlightperceptionandisclinicallyrecordedas"NLP",anabbreviationfor"nolightperception"."Blindness"isfrequentlyusedtodescribeseverewithresidualvision.Inordertodeterminewhichpeoplemayneedspecialassistancebecauseoftheirvisualdisabilities,variousgovernmentaljurisdictionshaveformulatedmorecomplexdefinitionsreferredtoaslegalblindness.InNorthAmericaandmostofEurope,legalblindnessisdefinedasvisualacuity(vision)of20/200(6/60)orlessinthebettereyewithbestcorrectionpossible.Thismeansthatalegallyblindindividualwouldhavetostand20feetfromanobjecttoseeitwiththesamedegreeofclarityasanormallysightedpersoncouldfrom200feet.Inmanyareas,peoplewithaverageacuitywhononethelesshaveavisualfieldoflessthan20degrees(thenormbeing60degrees)arealsoclassifiedasbeinglegallyblind.Approximatelytenpercentofthosedeemedlegallyblind,byanymeasure,arefullysightless.Theresthavesomevision,fromlightperceptionalonetorelativelygoodacuity.Thosewhoarenotlegallyblind,butnonethelesshaveseriousvisualimpairments,possesslowvision.

Bythe10thRevisionoftheWHOInternationalStatisticalClassificationofDiseases,InjuriesandCausesofDeath,lowvisionisdefinedasvisualacuityoflessthan6/18,butequaltoorbetterthan3/60,orcorrespondingvisualfieldlosstolessthan20degrees,inthebettereyewithbestpossiblecorrection.Blindnessisdefinedasvisualacuityoflessthan3/60,orcorrespondingvisualfieldlosstolessthan10degrees,inthebettereyewithbestpossiblecorrection.

Legalblindness

In1934,theAmericanMedicalAssociationadoptedthefollowingdefinitionofblindness:

"Centralvisualacuityof20/200orlessinthebettereyewithcorrectiveglassesorcentralvisualacuityofmorethan20/200ifthereisavisualfielddefectinwhichtheperipheralfieldiscontractedtosuchanextentthatthewidestdiameterofthevisualfieldsubtendsanangulardistancenogreaterthan20degreesinthebettereye."

TheUnitedStatesCongressincludedthisdefinitionaspartoftheAidtotheBlindprogramintheSocialSecurityActpassedin1935.In1972,theAidtotheBlindprogramandtwootherscombinedunderTitleXVIoftheSocialSecurityActtoformtheSupplementalSecurityIncomeprogramwhichcurrentlystates:

"Anindividualshallbeconsideredtobeblindforpurposesofthistitleifhehascentralvisualacuityof20/200orlessinthebettereyewiththeuseofacorrectinglens.Aneyewhichisaccompaniedbyalimitationinthefieldsofvisionsuchthatthewidestdiameterofthevisualfieldsubtendsananglenogreaterthan20degreesshallbeconsideredforpurposesofthefirstsentenceofthissubsectionashavingacentralvisualacuityof20/200orless.AnindividualshallalsobeconsideredtobeblindforpurposesofthistitleifheisblindasdefinedunderaStateplanapprovedundertitleXorXVIasineffectforOctober1972andreceivedaidundersuchplan(onthebasisofblindness)forDecember1973,solongasheiscontinuouslyblindassodefined."

Kuwaitisoneofmanynationsthatsharethesamecriteriaforlegalblindness.

Epidemiology(流行病学)

In1987,itwasestimatedthat598,000peopleintheUnitedStatesmetthelegaldefinitionofblindness.Ofthisnumber,58%wereovertheageof65.In1994-1995,millionAmericansreportedlegalblindness.

In2002,theWHOestimatedtherewere161million(about%oftheworldpopulation)visuallyimpairedpeopleintheworld,ofwhom124million(about2%)hadlowvisionand37million(about%)wereblind.

Causesofblindness

Seriousvisualimpairmenthasavarietyofcauses:

Diseases

Mostvisualimpairmentiscausedbydiseaseandmalnutrition.AccordingtoWHOestimatesin2002,themostcommoncausesofblindnessaroundtheworldare:

cataracts%),

glaucoma%),

age-relatedmaculardegeneration(AMD)%),

trachoma%),

cornealopacity%),and

diabeticretinopathy%),amongothercauses.

Peopleindevelopingcountriesaresignificantlymorelikelytoexperiencevisualimpairmentasaconsequenceoftreatableorpreventableconditionsthanaretheircounterpartsinthedevelopedworld.Whilevisionimpairmentismostcommoninpeopleoverage60acrossallregions,childreninpoorercommunitiesaremorelikelytobeaffectedbyblindingdiseasesthanaretheirmoreaffluentpeers.

Thelinkbetweenpovertyandtreatablevisualimpairmentismostobviouswhenconductingregionalcomparisonsofcause.MostadultvisualimpairmentinNorthAmericaandWesternEuropeisrelatedtoage-relatedmaculardegenerationanddiabeticretinopathy.Whilebothoftheseconditionsaresubjecttotreatment,neithercanbecured.

Indevelopingcountries,whereinpeoplehaveshorterlifeexpectancies,cataractsandwater-borneparasites—bothofwhichcanbetreatedeffectively—aremostoftentheculprits(seeRiverblindness,forexample).Oftheestimated40millionblindpeoplelocatedaroundtheworld,70–80%canhavesomeoralloftheirsightrestoredthroughtreatment.

Indevelopedcountrieswhereparasiticdiseasesarelesscommonandcataractsurgeryismoreavailable,age-relatedmaculardegeneration,glaucoma,anddiabeticretinopathyareusuallytheleadingcausesofblindness.

Abnormalitiesandinjuries

Eyeinjuries,mostoftenoccurringinpeopleunder30,aretheleadingcauseofmonocularblindness(visionlossinoneeye)throughouttheUnitedStates.Injuriesandcataractsaffecttheeyeitself,whileabnormalitiessuchasopticnervehypoplasiaaffectthenervebundlethatsendssignalsfromtheeyetothebackofthebrain,whichcanleadtodecreasedvisualacuity.

Peoplewithinjuriestotheoccipitallobeofthebraincan,despitehavingundamagedeyesandopticnerves,stillbelegallyortotallyblind.

Geneticdefects

Peoplewithalbinismoftensufferfromvisualimpairmenttotheextentthatmanyarelegallyblind,thoughfewofthemactuallycannotsee.

Recentadvancesinmappingthehumangenomehaveidentifiedothergeneticcausesoflowvisionorblindness.OnesuchexampleisBardet-Biedlsyndrome.

Poisoning

Asmallportionofallcasesofblindnessarecausedbytheintakeofcertainchemicals.Awell-knownexampleismethanolwhichisfoundinmethylatedspiritswhichissometimesusedbyalcoholicsasacheapsubstituteforregularalcoholicbeverages.

Blindnessprevention

Thereexistanumberoforganizations,suchasInternationalAgencyforthePreventionofBlindness,ORBISInternational,andSevaFoundation,whohavedevelopedprogramsaimedatpreventingblindness.

Adaptivetechniques

AtactilefeatureonaCanadianbanknote.

Visuallyimpairedandblindpeoplehavedevisedanumberoftechniquesthatallowthemtocompletedailyactivitiesusingtheirremainingsenses.Thesemightincludethefollowing:

Adaptationsofbanknotessothatthevaluecanbedeterminedbytouch.Forexample:

Insomecurrencies,suchastheeuro,poundsterlingandAustraliandollar,thesizeofanoteincreaseswithitsvalue.

Manybanknotesfromaroundtheworldhaveatactilefeaturetoindicatedenominationintheupperrightcorner.Thistactilefeatureisaseriesofraiseddots,butitisnotstandardBraille.

Itisalsopossibletofoldnotesindifferentwaystoassistrecognition.

Labelingandtaggingclothingandotherpersonalitems

Placingdifferenttypesoffoodatdifferentpositionsonadinnerplate

Markingcontrolsofhouseholdappliances

Mostpeople,oncetheyhavebeenvisuallyimpairedforlongenough,devisetheirownadaptivestrategiesinallareasofpersonalandprofessionalmanagement.

Tools

Watchfortheblind

Designers,bothvisuallyimpairedandsighted,havedevelopedanumberoftoolsforusebyblindpeople.

Mobility

Manypeoplewithseriousvisualimpairmentscantravelindependentlyassistedbytactilepavingand/orusingawhitecane,theinternationalsymbolofblindness.

Alongcaneisusedtoextendtheuser'srangeoftouchsensation,swunginalowsweepingmotionacrosstheintendedpathoftraveltodetectobstacles.However,somevisuallyimpairedpersonsdonotcarrythesekindsofcanes,optinginsteadfortheshorter,lighteridentification(ID)cane.Stillothersrequireasupportcane.

Eachoftheseispaintedwhiteformaximumvisibility,andtodenotevisualimpairmentonthepartoftheuser.Inadditiontomakingrulesaboutwhocanandcannotuseacane,somegovernmentsmandatetheright-of-waybegiventousersofwhitecanesorguidedogs.

Asmallnumberofpeople,aboutonepercent,employguidedogs.Thesecompanionsaretrainedtoleadblindindividualsaroundobstaclesonthegroundandoverhead.Thoughhighlyintelligent,guidedogscannotinterpretstreetsigns.Visuallyimpairedpeoplewhoemploytheseanimalsmustalreadybecompetenttravelers.

Readingandmagnification

Mostblindandvisuallyimpairedpeoplereadprint,eitherofaregularsizeorenlargedthroughtheuseofmagnificationdevices.Avarietyofmagnifyingglasses,someofwhicharehandheld,andsomeofwhichrestondesktops,canmakereadingeasierforthosewithdecreasedvisualacuity.

TherestreadBrailleandMoontypeorrelyontalkingbooksandreaders.TheyusecomputerswithspecialhardwaresuchasscannersandrefreshableBrailledisplaysaswellassoftwarewrittenspecificallyfortheblind,likeopticalcharacterrecognitionapplicationsandscreenreadingsoftware.

Somepeopleaccessthesematerialsthroughagenciesfortheblind,suchastheNationalLibraryServicefortheBlindandPhysicallyHandicappedintheUnitedStates,theNationalLibraryfortheBlindortheRNIBintheUnitedKingdom.

Closed-circuittelevisions,equipmentthatenlargesandcontraststextualitems,areamorehigh-techalternativetotraditionalmagnificationdevices.Sotooaremodernwebbrowsers,whichcanincreasethesizeoftextonsomewebpagesthroughbrowsercontrolsorthroughuser-controlledstylesheets.

Computers

AccesstechnologysuchasFreedomScientific'sJAWSforWindowsscreenreadingsoftwareenabletheblindtousemainstreamcomputerapplications.Mostlegallyblindpeople(70%ofthemacrossallages,accordingtotheLighthousefortheBlind)donotusecomputers.Onlyasmallfractionofthispopulation,whencomparedtothesightedcommuni